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DOE OSTI2020

Materials Data on In4Ag9 by Materials Project

Ag9In4 is gamma-brass-like structured and crystallizes in the cubic P-43m space group. The structure is three-dimensional. there are six inequivalent Ag sites. In the first Ag site, Ag is bonded in a 12-coordinate geometry to nine Ag and three equivalent In atoms. There are a spread of Ag–Ag bond distances ranging from 2.93–2.99 Å. All Ag–In bond lengths are 3.01 Å. In the second Ag site, Ag is bonded to six Ag and six In atoms to form distorted face-sharing AgIn6Ag6 cuboctahedra. There are three shorter (2.90 Å) and three longer (3.06 Å) Ag–Ag bond lengths. All Ag–In bond lengths are 3.01 Å. In the third Ag site, Ag is bonded in a 3-coordinate geometry to nine Ag and three equivalent In atoms. There are three shorter (2.99 Å) and three longer (3.09 Å) Ag–Ag bond lengths. All Ag–In bond lengths are 2.85 Å. In the fourth Ag site, Ag is bonded in a 4-coordinate geometry to seven Ag and six In atoms. There are one shorter (2.88 Å) and four longer (3.24 Å) Ag–Ag bond lengths. There are a spread of Ag–In bond distances ranging from 2.92–3.24 Å. In the fifth Ag site, Ag is bonded in a 11-coordinate geometry to six Ag and five In atoms. There are one shorter (2.84 Å) and one longer (3.12 Å) Ag–Ag bond lengths. There are a spread of Ag–In bond distances ranging from 2.93–3.00 Å. In the sixth Ag site, Ag is bonded in a 9-coordinate geometry to nine Ag and four equivalent In atoms. The Ag–Ag bond length is 2.90 Å. All Ag–In bond lengths are 3.17 Å. There are two inequivalent In sites. In the first In site, In is bonded in a 11-coordinate geometry to eleven Ag atoms. In the second In site, In is bonded in a 9-coordinate geometry to nine Ag atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In9Ag17 by Materials Project

Ag17In9 is gamma-brass-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are twenty-three inequivalent Ag sites. In the first Ag site, Ag is bonded in a 12-coordinate geometry to six Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.90–3.09 Å. There are a spread of Ag–In bond distances ranging from 2.97–3.01 Å. In the second Ag site, Ag is bonded in a 12-coordinate geometry to six Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.89–3.09 Å. There are a spread of Ag–In bond distances ranging from 2.97–3.02 Å. In the third Ag site, Ag is bonded in a 12-coordinate geometry to six Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.91–3.09 Å. There are a spread of Ag–In bond distances ranging from 2.97–3.03 Å. In the fourth Ag site, Ag is bonded in a 12-coordinate geometry to nine Ag and three In atoms. There are a spread of Ag–Ag bond distances ranging from 2.95–3.00 Å. All Ag–In bond lengths are 3.02 Å. In the fifth Ag site, Ag is bonded in a 12-coordinate geometry to eight Ag and four In atoms. There are a spread of Ag–Ag bond distances ranging from 2.94–3.01 Å. There are a spread of Ag–In bond distances ranging from 2.98–3.04 Å. In the sixth Ag site, Ag is bonded in a 12-coordinate geometry to seven Ag and five In atoms. There are a spread of Ag–Ag bond distances ranging from 2.95–3.01 Å. There are a spread of Ag–In bond distances ranging from 2.96–3.05 Å. In the seventh Ag site, Ag is bonded in a 11-coordinate geometry to five Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.96–3.23 Å. There are a spread of Ag–In bond distances ranging from 2.87–3.05 Å. In the eighth Ag site, Ag is bonded in a 11-coordinate geometry to six Ag and five In atoms. There are a spread of Ag–Ag bond distances ranging from 2.86–3.23 Å. There are a spread of Ag–In bond distances ranging from 2.95–2.99 Å. In the ninth Ag site, Ag is bonded in a 11-coordinate geometry to five Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.98–3.24 Å. There are a spread of Ag–In bond distances ranging from 2.89–3.06 Å. In the tenth Ag site, Ag is bonded in a 11-coordinate geometry to six Ag and five In atoms. There are a spread of Ag–Ag bond distances ranging from 2.87–3.23 Å. There are a spread of Ag–In bond distances ranging from 2.95–3.01 Å. In the eleventh Ag site, Ag is bonded in a 11-coordinate geometry to five Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.89–3.23 Å. There are a spread of Ag–In bond distances ranging from 2.96–3.21 Å. In the twelfth Ag site, Ag is bonded in a 11-coordinate geometry to five Ag and six In atoms. There are a spread of Ag–Ag bond distances ranging from 2.89–3.24 Å. There are a spread of Ag–In bond distances ranging from 2.96–3.20 Å. In the thirteenth Ag site, Ag is bonded in a 11-coordinate geometry to six Ag and five In atoms. There are a spread of Ag–Ag bond distances ranging from 2.87–3.22 Å. There are a spread of Ag–In bond distances ranging from 2.95–3.01 Å. In the fourteenth Ag site, Ag is bonded in a 12-coordinate geometry to seven Ag and five In atoms. The Ag–Ag bond length is 3.10 Å. There are a spread of Ag–In bond distances ranging from 2.89–3.12 Å. In the fifteenth Ag site, Ag is bonded in a 12-coordinate geometry to eight Ag and four In atoms. Both Ag–Ag bond lengths are 3.10 Å. There are a spread of Ag–In bond distances ranging from 2.86–3.11 Å. In the sixteenth Ag site, Ag is bonded in a 3-coordinate geometry to nine Ag and three In atoms. There are one shorter (3.09 Å) and two longer (3.10 Å) Ag–Ag bond lengths. All Ag–In bond lengths are 2.87 Å. In the seventeenth Ag site, Ag is bonded in a 4-coordinate geometry to seven Ag and six In atoms. The Ag–Ag bond length is 2.91 Å. There are a spread of Ag–In bond distances ranging from 2.90–3.27 Å. In the eighteenth Ag site, Ag is bonded in a 4-coordinate geometry to seven Ag and six In atoms. The Ag–Ag bond length is 2.88 Å. There are a spread of Ag–In bond distances ranging from 2.92–3.26 Å. In the nineteenth Ag site, Ag is bonded in a 4-coordinate geometry to seven Ag and six In atoms. There are a spread of Ag–In bond distances ranging from 2.89–3.25 Å. In the twentieth Ag site, Ag is bonded in a 4-coordinate geometry to seven Ag and six In atoms. There are a spread of Ag–In bond distances ranging from 2.91–3.27 Å. In the twenty-first Ag site, Ag is bonded in a 9-coordinate geometry to nine Ag and four In atoms. The Ag–Ag bond length is 2.91 Å. There are two shorter (3.16 Å) and two longer (3.18 Å) Ag–In bond lengths. In the twenty-second Ag site, Ag is bonded in a 1-coordinate geometry to eight Ag and five In atoms. There are a spread of Ag–In bond distances ranging from 2.88–3.21 Å. In the twenty-third Ag site, Ag is bonded in a 9-coordinate geometry to nine Ag and four In atoms. All Ag–In bond lengths are 3.17 Å. There are eleven inequivalent In sites. In the first In site, In is bonded in a 11-coordinate geometry to eleven Ag atoms. In the second In site, In is bonded in a 11-coordinate geometry to eleven Ag atoms. In the third In site, In is bonded in a 11-coordinate geometry to ten Ag and one In atom. The In–In bond length is 3.25 Å. In the fourth In site, In is bonded in a 11-coordinate geometry to ten Ag and one In atom. The In–In bond length is 3.22 Å. In the fifth In site, In is bonded in a 11-coordinate geometry to eleven Ag atoms. In the sixth In site, In is bonded in a 11-coordinate geometry to ten Ag and one In atom. The In–In bond length is 3.25 Å. In the seventh In site, In is bonded in a 11-coordinate geometry to nine Ag and two equivalent In atoms. Both In–In bond lengths are 3.21 Å. In the eighth In site, In is bonded in a 9-coordinate geometry to nine Ag and four In atoms. In the ninth In site, In is bonded in a 9-coordinate geometry to nine Ag atoms. In the tenth In site, In is bonded in a 9-coordinate geometry to nine Ag atoms. In the eleventh In site, In is bonded in a 9-coordinate geometry to nine Ag atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Membrane‐electrode assembly design parameters for optimal CO 2 reduction

Commercial-scale generation of carbon-containing chemicals and fuels by means of electrochemical CO 2 reduction (CO 2 R) requires electrolyzers operating at high current densities and product selectivities. Membrane-electrode assemblies (MEAs) have been shown to be suitable for this purpose. In such devices, the cathode catalyst layer controls both the rate of CO 2 R and the distribution of products. In this study, we investigate how the ionomer-to-catalyst ratio (I:Cat), catalyst loading, and catalyst-layer thickness influence the performance of a cathode catalyst layer containing Ag nanoparticles supported on carbon. In this paper, we explore how these parameters affect the cell performance and establish the role of the exchange solution (water vs. CsHCO 3 ) behind the anode catalyst layer in cell performance. We show that a high total current density is best achieved using an I:Cat ratio of 3 at a Ag loading of 0.01–0.1 mg Ag /cm 2 and with a 1.0 M solution of CsHCO 3 circulated behind the anode catalyst layer. For these conditions, the optimal CO partial current density depends on the voltage applied to the MEA. The work also reveals that the performance of the cathode catalyst layer is limited by a combination of the electrochemically active surface area and the degree to which mass transfer of CO 2 to the surface of the Ag nanoparticles and the transport of OH – anions away from it limit the overall catalyst activity. Hydration of the ionomer in the cathode catalyst layer is found not to be an issue when using an exchange solution. The insights gained allowed for a Ag CO 2 R MEA that operates between 200 mA/cm 2 and 1 A/cm 2 with CO faradaic efficiencies of 78–91%, and the findings and understanding gained herein should be applicable to a broad range of CO 2 R MEA-based devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ca2Al11Si13Ag7O48 by Materials Project

Ca2Ag7Al11Si13O48 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a pentagonal planar geometry to five O atoms. There are a spread of Ca–O bond distances ranging from 2.19–2.48 Å. In the second Ca site, Ca is bonded in a pentagonal planar geometry to five O atoms. There are a spread of Ca–O bond distances ranging from 2.18–2.54 Å. There are seven inequivalent Ag sites. In the first Ag site, Ag is bonded in a distorted trigonal planar geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.17–2.50 Å. In the second Ag site, Ag is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.18–2.47 Å. In the third Ag site, Ag is bonded in a 4-coordinate geometry to four O atoms. There are a spread of Ag–O bond distances ranging from 2.26–2.57 Å. In the fourth Ag site, Ag is bonded in a 4-coordinate geometry to four O atoms. There are a spread of Ag–O bond distances ranging from 2.26–2.66 Å. In the fifth Ag site, Ag is bonded in a distorted L-shaped geometry to two O atoms. There are one shorter (2.29 Å) and one longer (2.37 Å) Ag–O bond lengths. In the sixth Ag site, Ag is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.19–2.48 Å. In the seventh Ag site, Ag is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.20–2.44 Å. There are eleven inequivalent Al sites. In the first Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.74–1.81 Å. In the second Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.83 Å. In the third Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.80 Å. In the fourth Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.74–1.78 Å. In the fifth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.74–1.80 Å. In the sixth Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.73–1.83 Å. In the seventh Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.80 Å. In the eighth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.68–1.85 Å. In the ninth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.81 Å. In the tenth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.68–1.83 Å. In the eleventh Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.68–1.86 Å. There are thirteen inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.57–1.67 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.58–1.66 Å. In the fifth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.59–1.66 Å. In the sixth Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.60 Å) and two longer (1.66 Å) Si–O bond length. In the seventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.69 Å. In the eighth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the ninth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the tenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the eleventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the twelfth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.63 Å) and two longer (1.64 Å) Si–O bond length. In the thirteenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. There are forty-eight inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the seventh O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the eighth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the ninth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the tenth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the eleventh O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the twelfth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the thirteenth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the fourteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixteenth O site, O is bonded in a distorted linear geometry to one Ag, one Al, and one Si atom. In the seventeenth O site, O is bonded in a linear geometry to one Al and one Si atom. In the eighteenth O site, O is bonded in a distorted linear geometry to one Ag, one Al, and one Si atom. In the nineteenth O site, O is bonded in a linear geometry to two Si atoms. In the twentieth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag, one Al, and one Si atom. In the twenty-first O site, O is bonded in a 2-coordinate geometry to one Ag and two Al atoms. In the twenty-second O site, O is bonded in a distorted bent 150 degrees geometry to one Ag, one Al, and one Si atom. In the twenty-third O site, O is bonded in a 2-coordinate geometry to one Ag and two Al atoms. In the twenty-fourth O site, O is bonded in a 2-coordinate geometry to one Ag and two Al atoms. In the twenty-fifth O site, O is bonded in a bent 120 degrees geometry to two Al atoms. In the twenty-sixth O site, O is bonded in a bent 120 degrees geometry to two Al atoms. In the twenty-seventh O site, O is bonded in a distorted bent 120 degrees geometry to one Al and one Si atom. In the twenty-eighth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Al atoms. In the twenty-ninth O site, O is bonded in a 2-coordinate geometry to one Ag and two Al atoms. In the thirtieth O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and two Al atoms. In the thirty-first O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and two Al atoms. In the thirty-second O site, O is bonded in a 3-coordinate geometry to one Ca and two Al atoms. In the thirty-third O site, O is bonded in a 2-coordinate geometry to one Ag and two Al atoms. In the thirty-fourth O site, O is bonded in a 4-coordinate geometry to two Ca and two Al atoms. In the thirty-fifth O site, O is bonded in a 3-coordinate geometry to one Ca and two Al atoms. In the thirty-sixth O site, O is bonded in a bent 150 degrees geometry to two Al atoms. In the thirty-seventh O site, O is bonded in a linear geometry to two Al atoms. In the thirty-eighth O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the thirty-ninth O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the fortieth O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the forty-first O site, O is bonded in a distorted bent 150 degrees geometry to one Ag, one Al, and one Si atom. In the forty-second O site, O is bonded in a 2-coordinate geometry to one Ca, one Al, and one Si atom. In the forty-third O site, O is bonded in a 2-coordinate geometry to one Ca, one Al, and one Si atom. In the forty-fourth O site, O is bonded in a 2-coordinate geometry to one Ca, one Al, and one Si atom. In the forty-fifth O site, O is bonded in a 2-coordinate geometry to one Ca, one Al, and one Si atom. In the forty-sixth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the forty-seventh O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the forty-eighth O site, O is bonded in a bent 150 degrees geometry to two Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Gaseous Iodine Sorbents: A Comparison between Ag-Loaded Aerogel and Xerogel Scaffolds

The general properties of aluminosilicate aerogels and xerogels with silver nanoparticles as sorbents for capturing iodine gas [I2(g)] were investigated. The structures, morphologies, compositions, and pore structures of aerogel and xerogel were compared using powder X-ray diffraction (PXRD), scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, as well as specific surface area (SSA) and pore size analyses. The as-made aerogels, xerogels, and heat-treated aerogels were impregnated with Ag by aqueous ion exchange using AgNO3 solutions, and PXRD patterns showed the presence of nanocrystalline Ag0 after Ag-impregnation. Iodine loadings of aerogels and xerogels were 0.33–0.41 g g-1. The Ag-impregnated aerogels without heat-treatment showed an 8 mass% higher iodine loading than Ag-impregnated xerogels and 3 mass% higher than heat-treated Ag-impregnated aerogels. All gels after iodine uptake showed the presence of AgI, indicating chemisorption of iodine to silver. The SSA values of the as-made gels were 419–598 m2 g-1 but decreased significantly to 34–120 m2 g-1 after Ag-impregnation and iodine uptake processes. Overall, changes in physical and chemical properties of aerogels and xerogels after iodine uptake were similar, and the difference in iodine loading capacities of the aerogels and xerogels was not significant while the synthesis process of xerogel is more practical because it does not require supercritical drying.

aerogel, xerogel, iodine capture↗
DOE OSTI2020

Materials Data on CoAg3(CN)6 by Materials Project

Co(Ag(CN)2)3 crystallizes in the trigonal P-31m space group. The structure is zero-dimensional and consists of one cobalt molecule and three Ag(CN)2 clusters. In each Ag(CN)2 cluster, Ag1+ is bonded in a linear geometry to two equivalent N3- atoms. Both Ag–N bond lengths are 2.05 Å. C+2.33+ is bonded in a distorted single-bond geometry to one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a linear geometry to one Ag1+ and one C+2.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeAg3(CN)6 by Materials Project

Fe(Ag(CN)2)3 crystallizes in the trigonal P-31m space group. The structure is zero-dimensional and consists of one iron molecule and three Ag(CN)2 clusters. In each Ag(CN)2 cluster, Ag1+ is bonded in a linear geometry to two equivalent N3- atoms. Both Ag–N bond lengths are 2.04 Å. C2+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a linear geometry to one Ag1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Layered and Low-Dimensional Lead, Silver, and Bismuth Halide Perovskites Directed by Halogen-Substituted Spacer Cations

Hybrid organic–inorganic metal halides provide a diverse parameter space in which the optoelectronic properties can be tuned through the composition. The compositional tunability extends to the metal site, which can be expanded from single valent metals (e.g., Pb 2+ ) to multivalent metals (e.g., Ag + and Bi 3+ ), and the dimension (2D, 1D, or 0D). However, a deeper understanding of how the organic cations template these metal halide structures is needed. Here, we synthesize and study the structures of a series of new layered and low-dimensional metal (Pb, Ag, and Bi) halides templated by the halogenated aryl spacer cations 2-chlorobenzylammonium (2ClBZ) and 3-chloro-2-fluorobenzylammonium (3Cl2FBZ). We report new lead perovskites, (3Cl2FBZ) 2 PbBr 4 , (2ClBZ) 3 PbI 5 , and (3Cl2FBZ) 2 PbI 4 , and compare them to their silver and/or bismuth analogs (2ClBZ) 4 AgBiBr 8 , (3Cl2FBZ) 4 AgBiBr 8 , (2ClBZ) 3 Bi 2 I 9 , and (3Cl2FBZ) 4 Bi 2 I 10 . In all structures, the halogen-substituted cations result in 2D or “pseudo-2D” layering, but the different halogen substituents introduce different distortions (tilting, octahedral distortion) and dimensional reduction to 1D or 0D depending on the metal and halide compositions. Optical absorption measurements reveal the bandgaps are tunable through metal sites, dimension, and cations to different extents. Furthermore, the 1D (3Cl2FBZ) 4 Bi 2 I 10 crystallizes in the noncentrosymmetric space group Cmc2 1 and exhibits second-harmonic generation (SHG). Furthermore, the organic–inorganic interactions and resultant structural distortions examined here provide insights toward the engineering of noncentrosymmetry and dimensional control in hybrid metal halide perovskites.

Cations↗
DOE OSTI2025

Trinuclear Copper(I) and Silver(I) Complexes of a Pentafluorosulfanyl-Decorated Pyrazolate

Here, this study reports the synthesis and characterization of the first fluorinated coinage metal pyrazolates with SF 5 groups, specifically {[3-(SF 5 )­Pz]­M} 3 (M = Cu, Ag), and compares them to trifluoromethylated analogs. X-ray analysis reveals different pyrazolyl ligand orientations and metallophilic interactions, as well as supramolecular structures influenced by fluorinated substituents and metals. The {[3-(SF 5 )­Pz]­M} 3 complexes form face-to-face sandwich adducts with benzene. Photophysical investigations show that copper complexes exhibit long-lived phosphorescence, while silver analogs display fast fluorescence, with emission properties modulated by substituents, solvent environment, and intermolecular interactions. Computational studies confirm the experimental geometries and demonstrate that SF 5 substituents increase the π-acidity and enhance arene binding over the analogs featuring the smaller and less-electron-withdrawing CF 3 groups and provide insights into metallophilic interactions and photoluminescence. These newly uncovered SF 5 decorated materials, with enhanced π-acidity and arene-binding ability, are promising materials for molecular sensing and tunable luminescence.

Vanga, Mukundam [University of Texas, Arlington, T↗
DOE OSTI2025

Optimization and quantification of silver( II ) for mediated electrochemical oxidation applications

Mediated electrochemical oxidation (MEO) is a low-temperature, low-pressure, aqueous mineralization process used to treat organic waste. A powerful metal oxidant is used as a mediator in an acidic solution. Although Ce and Co are thoroughly studied mediators, Ag is a preferred choice because of the higher efficiency rates of mineralization observed with this system. Importantly, the quantification methodology and spectroscopic characteristics of the Ag(II) ion must be obtained. In this study, we determined molar extinction coefficients of the primary absorption band associated with the Ag(II) ion in 2–9 M HNO 3 solution. The optimization of Ag(II) electrooxidation was also determined by altering parameters such as HNO 3 concentration, mediator concentration, and temperature. The optimization studies and extinction coefficient data provide parameters for implementation of Ag as a suitable mediator for MEO processing of organic waste.

Schrage, Briana R. [Oak Ridge National Laboratory ↗
DOE OSTI2022

Silver-Loaded Xerogel Nanostructures for Iodine Capture: A Comparison of Thiolated versus Unthiolated Sorbents

Here this paper describes the development and provides comparisons of thiolated (-SH) and unthiolated Ag-Al-Si-O xerogels for iodine gas capture. These xerogels were produced from alkoxides and then heat-treated at 350 °C to provide mechanical strength for subsequent processing steps. Then, a portion of the xerogels was thiolated using (3-mercaptopropyl)trimethoxysilane. Next, thiolated and unthiolated batches were ion-exchanged in AgNO 3 solutions where Ag + replaced Na + in the gel network on a near 1:1 molar basis. Subsamples of the Ag-exchanged xerogels were subjected to a reduction step in H 2 /Ar to convert Ag + to Ag 0 where the rest of the Ag-exchanged (Ag + ) were not reduced. X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy revealed nanoscale Ag 0 in the Ag + samples despite no active reduction where actively reduced samples had bimodal Ag 0 distribution of ~2-3 nm hexagonal and ~6-7 nm cubic crystallites. Synchrotron X-ray absorption spectroscopy was used to assess the oxidization states of Ag, S, and I within the different xerogel samples. The specific surface areas of the base xerogels decreased as subsequent treatments were performed on the as-made samples, albeit the decreases were smaller than aerogel equivalents of these samples from a previous study. All iodine-loaded Ag-based samples showed a mixture of β-AgI and γ-AgI. Comparisons of iodine-loading results with other Ag-based iodine sorbents show that the thiolated Ag 0 -xerogels in this work have one of the highest iodine-loading capacities (q e ) reported to date in saturated conditions with the thiolated Ag 0 -xerogel showing 522 mg iodine per g of the sorbent.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Chemical Modifications of Ag Catalyst Surfaces with Imidazolium Ionomers Modulate H 2 Evolution Rates during Electrochemical CO 2 Reduction

Bridging polymer design with catalyst surface science is a promising direction for tuning and optimizing electrochemical reactors that could impact long-term goals in energy and sustainability. Particularly, the interaction between inorganic catalyst surfaces and organic-based ionomers provides an avenue to both steer reaction selectivity and promote activity. In this work, we studied the role of imidazolium-based ionomers for electrocatalytic CO 2 reduction to CO (CO 2 R) on Ag surfaces and found that they produce no effect on CO 2 R activity yet strongly promote the competing hydrogen evolution reaction (HER). By examining the dependence of HER and CO 2 R rates on concentrations of CO 2 and HCO 3 –, we developed a kinetic model that attributes HER promotion to intrinsic promotion of HCO 3 – reduction by imidazolium ionomers. We also show that varying the ionomer structure by changing substituents on the imidazolium ring modulates the HER promotion. This ionomer-structure dependence was analyzed via Taft steric parameters and density functional theory calculations, which suggest that steric bulk from functionalities on the imidazolium ring reduces access of the ionomer to both HCO 3 – and the Ag surface, thus limiting the promotional effect. Our results help develop design rules for ionomer–catalyst interactions in CO 2 R and motivate further work into precisely uncovering the interplay between primary and secondary coordination in determining electrocatalytic behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Elucidating the Roles of Local and Nonlocal Rate Enhancement Mechanisms in Plasmonic Catalysis

Plasmonic metal nanoparticles (e.g., Ag, Au, and Cu) constitute a class of materials that interact with light via the excitation of localized surface plasmon resonance (LSPR). Numerous studies have reported substantial enhancements in the rates of chemical reactions on illuminated plasmonic nanoparticle catalysts compared to corresponding systems in the absence of illumination. There are two mechanisms that have been proposed to explain the LSPR-induced chemical reactivity. One mechanism assumes a local plasmon-induced hot charge-carrier-mediated activation of the reactants, while the other assumes an LSPR-induced equilibrium heating of the catalyst, which leads to energy transfer to and chemical reaction of the adsorbed reactants. Here, in this contribution, we developed a setup amenable to accurate in situ catalyst temperature and kinetic reaction rate measurements. We employed this setup to study the LSPR-induced rate enhancement in a case study of the CO oxidation reaction on plasmonic, monometallic Ag nanoparticle catalysts supported on α-Al 2 O 3 . We explored various Ag loadings and clustering levels. Our data show that the equilibrium heating of the catalyst cannot fully explain the illumination-induced plasmonic rate enhancements. This is the case even for high loading and clustering of Ag nanoparticles, where the equilibrium heating significantly increases. Based on the analysis, we propose that local effects, related to the plasmon-induced activation of adsorbates (reactants) via electronic excitation of the reactant or photothermal heating of the reactants that is highly localized to the individual nanoparticles, play a critical role in driving LSPR-induced chemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Al12Si12Ag16S5O48 by Materials Project

Ag16Al12Si12S5O48 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are sixteen inequivalent Ag sites. In the first Ag site, Ag is bonded to one S and three O atoms to form distorted AgSO3 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Ag–S bond length is 2.43 Å. There are a spread of Ag–O bond distances ranging from 2.46–2.53 Å. In the second Ag site, Ag is bonded to one S and three O atoms to form AgSO3 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Ag–S bond length is 2.40 Å. There are a spread of Ag–O bond distances ranging from 2.35–2.40 Å. In the third Ag site, Ag is bonded to one S and three O atoms to form AgSO3 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Ag–S bond length is 2.41 Å. There are two shorter (2.36 Å) and one longer (2.41 Å) Ag–O bond lengths. In the fourth Ag site, Ag is bonded to one S and three O atoms to form distorted AgSO3 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Ag–S bond length is 2.57 Å. There are a spread of Ag–O bond distances ranging from 2.46–2.49 Å. In the fifth Ag site, Ag is bonded in a distorted rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.40 Å. There are a spread of Ag–O bond distances ranging from 2.51–2.59 Å. In the sixth Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.42 Å. There are a spread of Ag–O bond distances ranging from 2.55–2.61 Å. In the seventh Ag site, Ag is bonded to one S and three O atoms to form distorted AgSO3 trigonal pyramids that share corners with three AlO4 tetrahedra, corners with three SiO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. The Ag–S bond length is 2.40 Å. There are a spread of Ag–O bond distances ranging from 2.51–2.57 Å. In the eighth Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.40 Å. There are a spread of Ag–O bond distances ranging from 2.51–2.62 Å. In the ninth Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.42 Å. There are a spread of Ag–O bond distances ranging from 2.50–2.61 Å. In the tenth Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.41 Å. There are a spread of Ag–O bond distances ranging from 2.50–2.60 Å. In the eleventh Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.40 Å. There are a spread of Ag–O bond distances ranging from 2.52–2.64 Å. In the twelfth Ag site, Ag is bonded to one S and three O atoms to form distorted AgSO3 trigonal pyramids that share corners with three AlO4 tetrahedra, corners with three SiO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. The Ag–S bond length is 2.41 Å. There are one shorter (2.50 Å) and two longer (2.54 Å) Ag–O bond lengths. In the thirteenth Ag site, Ag is bonded to one S and three O atoms to form AgSO3 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Ag–S bond length is 2.41 Å. There are a spread of Ag–O bond distances ranging from 2.35–2.41 Å. In the fourteenth Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.41 Å. There are a spread of Ag–O bond distances ranging from 2.45–2.64 Å. In the fifteenth Ag site, Ag is bonded in a rectangular see-saw-like geometry to one S and three O atoms. The Ag–S bond length is 2.40 Å. There are a spread of Ag–O bond distances ranging from 2.51–2.56 Å. In the sixteenth Ag site, Ag is bonded to one S and three O atoms to form AgSO3 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Ag–S bond length is 2.41 Å. There are a spread of Ag–O bond distances ranging from 2.34–2.40 Å. There are twelve inequivalent Al sites. In the first Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra and corners with four SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.75–1.78 Å. In the second Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with four SiO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. There are a spread of Al–O bond distances ranging from 1.75–1.77 Å. In the third Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra, corners with four SiO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. There are a spread of Al–O bond distances ranging from 1.75–1.77 Å. In the fourth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra, corners with four SiO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. There is one shorter (1.76 Å) and three longer (1.77 Å) Al–O bond length. In the fifth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four SiO4 tetrahedra. There is two shorter (1.75 Å) and two longer (1.77 Å) Al–O bond length. In the sixth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four SiO4 tetrahedra. There is two shorter (1.76 Å) and two longer (1.77 Å) Al–O bond length. In the seventh Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra and corners with four SiO4 tetrahedra. There is two shorter (1.76 Å) and two longer (1.77 Å) Al–O bond length. In the eighth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four SiO4 tetrahedra. All Al–O bond lengths are 1.76 Å. In the ninth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with four SiO4 tetrahedra, and corners with two AgSO3 trigonal pyramids. There is one shorter (1.76 Å) and three longer (1.77 Å) Al–O bond length. In the tenth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra and a cornercorner with one AgSO3 trigonal pyramid. There is three shorter (1.76 Å) and one longer (1.77 Å) Al–O bond length. In the eleventh Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four SiO4 tetrahedra. There is two shorter (1.75 Å) and two longer (1.77 Å) Al–O bond length. In the twelfth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four SiO4 tetrahedra. There is two shorter (1.76 Å) and two longer (1.77 Å) Al–O bond length. There are twelve inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There is three shorter (1.64 Å) and one longer (1.65 Å) Si–O bond length. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AgSO3 tetrahedra, corners with four AlO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with four AlO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. All Si–O bond lengths are 1.64 Å. In the fifth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There is one shorter (1.63 Å) and three longer (1.64 Å) Si–O bond length. In the sixth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with four AlO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. There is three shorter (1.64 Å) and one longer (1.65 Å) Si–O bond length. In the seventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There is one shorter (1.63 Å) and three longer (1.64 Å) Si–O bond length. In the eighth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the ninth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with four AlO4 tetrahedra, and a cornercorner with one AgSO3 trigonal pyramid. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the tenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There is two shorter (1.64 Å) and two longer (1.65 Å) Si–O bond length. In the eleventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AgSO3 tetrahedra and corners with four AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the twelfth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AgSO3 tetrahedra, corners with four AlO4 tetrahedra, and corners with two AgSO3 trigonal pyramids. There is two shorter (1.64 Å) and two longer (1.65 Å) Si–O bond length. There are five inequivalent S sites. In the first S site, S is bonded in a 3-coordinate geometry to two Ag and one S atom. The S–S bond length is 1.97 Å. In the second S site, S is bonded in a tetrahedral geometry to four Ag atoms. In the third S site, S is bonded in a tetrahedral geometry to four Ag atoms. In the fourth S site, S is bonded in a tetrahedral geometry to four Ag atoms. In the fifth S site, S is bonded in a 3-coordinate geometry to two Ag and one S atom. There are forty-eight inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the second O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the third O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the fourth O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the fifth O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the sixth O site, O is bonded in a distorted trigonal planar geometry to one Ag, one Al, and one Si atom. In the seventh O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the eighth O site, O is bonded in a 3-coordinate geometry to one Ag, one Al, and one Si atom. In the ninth O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the tenth O site, O is bonded in a distorted trigonal planar geometry to one Ag, one Al, and one Si atom. In

36 MATERIALS SCIENCE↗
DOE OSTI2024

Structural Distortions and Short‐Range Magnetism in a Honeycomb Iridate Cu 3 ZnIr 2 O 6

Layered honeycomb iridates receive significant attention in the materials chemistry and physics fields due to the relevance of their crystal structures to the Kitaev model of a quantum spin liquid (QSL). In quest of liquid‐like magnetic ground state signatures, first‐generation alkali metal iridates A 2 IrO 3 ≡ A 3 [AIr 2 ]O 6 (A = Li, Na) and second‐generation iridates T 3 [AIr 2 ]O 6 ( T = Cu, Ag, H) are developed. T 3 [AIr 2 ]O 6 is synthesized from A 3 [AIr 2 ]O 6 via metathesis reactions replacing alkali ions located between honeycomb layers. Herein, the next level of chemical and structural complexity is introduced by synthesizing the honeycomb iridate, Cu 3 ZnIr 2 O 6 , in which alkali ions between and within the honeycomb layers are both selectively exchanged with two different transition metals. Analysis of powder X‐Ray diffraction data reveals corrugation of the honeycomb layers in Cu 3 ZnIr 2 O 6 that hinders complete magnetic frustration and results in a spin glass behavior observed from magnetization and specific heat data. Thus, Cu 3 ZnIr 2 O 6 represents yet another model, which broadens understanding of intricate relationships between intralayer distortions and magnetism of prospective Kitaev QSL compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr5Al4(AgGe2)2 by Materials Project

Pr5Al4(AgGe2)2 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are five inequivalent Pr sites. In the first Pr site, Pr is bonded to two equivalent Ag, eight Al, and two equivalent Ge atoms to form a mixture of edge and face-sharing PrAl8Ag2Ge2 cuboctahedra. Both Pr–Ag bond lengths are 3.49 Å. There are four shorter (3.25 Å) and four longer (3.39 Å) Pr–Al bond lengths. Both Pr–Ge bond lengths are 3.22 Å. In the second Pr site, Pr is bonded to six Ag, two equivalent Al, and four equivalent Ge atoms to form a mixture of distorted edge and face-sharing PrAl2Ag6Ge4 cuboctahedra. There are two shorter (3.25 Å) and four longer (3.40 Å) Pr–Ag bond lengths. Both Pr–Al bond lengths are 3.51 Å. All Pr–Ge bond lengths are 3.24 Å. In the third Pr site, Pr is bonded to four equivalent Ag, two equivalent Al, and six Ge atoms to form a mixture of edge and face-sharing PrAl2Ag4Ge6 cuboctahedra. All Pr–Ag bond lengths are 3.33 Å. Both Pr–Al bond lengths are 3.26 Å. There are four shorter (3.29 Å) and two longer (3.44 Å) Pr–Ge bond lengths. In the fourth Pr site, Pr is bonded to six Al and six Ge atoms to form a mixture of edge and face-sharing PrAl6Ge6 cuboctahedra. There are two shorter (3.28 Å) and four longer (3.30 Å) Pr–Al bond lengths. There are two shorter (3.28 Å) and four longer (3.30 Å) Pr–Ge bond lengths. In the fifth Pr site, Pr is bonded to six Al and six Ge atoms to form a mixture of edge and face-sharing PrAl6Ge6 cuboctahedra. There are four shorter (3.29 Å) and two longer (3.33 Å) Pr–Al bond lengths. There are two shorter (3.26 Å) and four longer (3.30 Å) Pr–Ge bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 3-coordinate geometry to six Pr, two equivalent Al, and one Ge atom. Both Ag–Al bond lengths are 2.51 Å. The Ag–Ge bond length is 2.58 Å. In the second Ag site, Ag is bonded in a 9-coordinate geometry to six Pr and three Ge atoms. All Ag–Ge bond lengths are 2.55 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded in a distorted trigonal planar geometry to six Pr and three Ge atoms. There are two shorter (2.49 Å) and one longer (2.50 Å) Al–Ge bond lengths. In the second Al site, Al is bonded in a distorted trigonal planar geometry to six Pr and three Ge atoms. All Al–Ge bond lengths are 2.49 Å. In the third Al site, Al is bonded in a distorted bent 120 degrees geometry to six Pr, one Al, and two equivalent Ge atoms. The Al–Al bond length is 2.58 Å. Both Al–Ge bond lengths are 2.52 Å. In the fourth Al site, Al is bonded in a distorted bent 120 degrees geometry to six Pr, two equivalent Ag, and one Al atom. There are four inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six Pr and three Ag atoms. In the second Ge site, Ge is bonded in a 3-coordinate geometry to six Pr, one Ag, and two equivalent Al atoms. In the third Ge site, Ge is bonded in a distorted trigonal planar geometry to six Pr and three Al atoms. In the fourth Ge site, Ge is bonded in a 3-coordinate geometry to six Pr and three Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Polymorphic Metastability in Colloidal Semiconductor Nanocrystals

Metastable polymorphs of inorganic solids often possess material properties not present in the corresponding thermodynamic polymorphs, making them targets for the development of new functional materials. In contrast with isolating metastable bulk materials, syntheses of metastable polymorphs on the nanoscale are aided by fast non-equilibrium reaction kinetics and the favorable thermodynamic influence of surface energies, giving rise to greater ease of access to metastable high-temperature polymorphs and, in some cases, new polymorphs that do not exist in the bulk. The syntheses of metastable semiconductor nanocrystals are of interest for their potentially unique optoelectronic and physicochemical properties. However, in many material systems, synthesizing nanocrystalline products away from thermodynamic equilibrium in a predictable manner remains an outstanding challenge. This review outlines direct synthetic methodologies that have been developed to enable control over the nucleation and growth of metastable polymorphs of semiconductor nanocrystals by tailoring reaction conditions, precursor kinetics, ligand and surface effects, and other synthetic levers. The case studies reviewed herein expound on the direct syntheses of metastable ZnSe, Cu 2 SnSe 3 , CuInSe 2 , Ag 2 Se, and AgInSe 2 nanocrystals, and although there remain numerous examples of metastable nanocrystal syntheses outside of these metal chalcogenide systems, the concepts discussed are of general utility to the field of metastable nanocrystal syntheses as a whole. Explicit examples in which new functional properties are afforded by metastable polymorphs of the aforementioned material systems are presented within the context of applications for solar cells, photonics, and optical sensing. Finally, the factors that affect the kinetic persistence of metastable nanocrystalline polymorphs are discussed at length for these material systems.

36 MATERIALS SCIENCE↗