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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Electronic impact of Ni2P nanoparticle size on hydrogenation rates

Nickle phosphide, Ni2P, nanoparticles supported on SiO2 show a marked volcano shaped size dependence. Kinetic analysis and physicochemical characterization shows the electron density of Ni to increase with increasing Ni2P size, enhancing in turn the H2 adsorption strength. For particles below 15 nm, H adsorbs weakly causing a low surface coverage of H, gradually increasing with particle size. For large particles, hydrogen binds too strongly causing a high coverage but low catalytic activity. The remarkable size dependence of the electronic properties show that Ni2P particle size can be used to fine-tune its activity for hydrogenation.

Ni2P size effect, Electron density, H2 adsorption ↗
DOE OSTI2020

Materials Data on Ni2P by Materials Project

Ni2P crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Ni+1.50+ sites. In the first Ni+1.50+ site, Ni+1.50+ is bonded to five P3- atoms to form distorted NiP5 trigonal bipyramids that share corners with six equivalent NiP4 tetrahedra, corners with ten equivalent NiP5 trigonal bipyramids, edges with six equivalent NiP4 tetrahedra, and edges with six equivalent NiP5 trigonal bipyramids. There are one shorter (2.34 Å) and four longer (2.46 Å) Ni–P bond lengths. In the second Ni+1.50+ site, Ni+1.50+ is bonded to four P3- atoms to form NiP4 tetrahedra that share corners with ten equivalent NiP4 tetrahedra, corners with six equivalent NiP5 trigonal bipyramids, edges with two equivalent NiP4 tetrahedra, and edges with six equivalent NiP5 trigonal bipyramids. There are two shorter (2.21 Å) and two longer (2.27 Å) Ni–P bond lengths. There are two inequivalent P3- sites. In the first P3- site, P3- is bonded in a 9-coordinate geometry to nine Ni+1.50+ atoms. In the second P3- site, P3- is bonded in a 9-coordinate geometry to nine Ni+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Ni2P)2 by Materials Project

U(Ni2P)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. U is bonded to twelve equivalent Ni and six equivalent P atoms to form distorted face-sharing UNi12P6 octahedra. There are eight shorter (3.07 Å) and four longer (3.09 Å) U–Ni bond lengths. There are two shorter (2.80 Å) and four longer (2.83 Å) U–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent U and three equivalent P atoms. There are two shorter (2.31 Å) and one longer (2.33 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent U and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(Ni2P)2 by Materials Project

Tb(Ni2P)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Tb is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.81 Å) and four longer (2.86 Å) Tb–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.31 Å) and one longer (2.32 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Tb and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy(Ni2P)2 by Materials Project

Dy(Ni2P)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Dy is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.81 Å) and four longer (2.85 Å) Dy–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.30 Å) and one longer (2.32 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Dy and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(Ni2P)2 by Materials Project

Ho(Ni2P)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ho is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.79 Å) and four longer (2.83 Å) Ho–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.30 Å) and one longer (2.31 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Ho and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Ni2P)2 by Materials Project

YbNi4P2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Yb2+ is bonded to six equivalent P3- atoms to form a mixture of corner and edge-sharing YbP6 octahedra. The corner-sharing octahedral tilt angles are 38°. There are two shorter (2.78 Å) and four longer (2.85 Å) Yb–P bond lengths. Ni1+ is bonded in a trigonal planar geometry to three equivalent P3- atoms. There are two shorter (2.28 Å) and one longer (2.30 Å) Ni–P bond lengths. P3- is bonded in a 9-coordinate geometry to three equivalent Yb2+ and six equivalent Ni1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(Ni2P)2 by Materials Project

SmNi4P2 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. there are two inequivalent Sm2+ sites. In the first Sm2+ site, Sm2+ is bonded in a 6-coordinate geometry to six P3- atoms. There are a spread of Sm–P bond distances ranging from 2.89–2.94 Å. In the second Sm2+ site, Sm2+ is bonded to six P3- atoms to form SmP6 octahedra that share corners with six equivalent NiP4 tetrahedra, edges with two equivalent SmP6 octahedra, and edges with four equivalent NiP4 tetrahedra. There are two shorter (2.86 Å) and four longer (2.91 Å) Sm–P bond lengths. There are six inequivalent Ni1+ sites. In the first Ni1+ site, Ni1+ is bonded in a trigonal non-coplanar geometry to three P3- atoms. There are one shorter (2.18 Å) and two longer (2.27 Å) Ni–P bond lengths. In the second Ni1+ site, Ni1+ is bonded in a bent 120 degrees geometry to two P3- atoms. There are one shorter (2.25 Å) and one longer (2.31 Å) Ni–P bond lengths. In the third Ni1+ site, Ni1+ is bonded in a water-like geometry to two equivalent P3- atoms. Both Ni–P bond lengths are 2.30 Å. In the fourth Ni1+ site, Ni1+ is bonded to four P3- atoms to form NiP4 tetrahedra that share corners with three equivalent SmP6 octahedra, corners with three NiP4 tetrahedra, and edges with two equivalent NiP4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–58°. There are a spread of Ni–P bond distances ranging from 2.22–2.38 Å. In the fifth Ni1+ site, Ni1+ is bonded to four P3- atoms to form NiP4 tetrahedra that share corners with three NiP4 tetrahedra, edges with two equivalent SmP6 octahedra, and edges with two equivalent NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.30–2.48 Å. In the sixth Ni1+ site, Ni1+ is bonded in a trigonal planar geometry to three P3- atoms. There are two shorter (2.27 Å) and one longer (2.38 Å) Ni–P bond lengths. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 9-coordinate geometry to two equivalent Sm2+ and seven Ni1+ atoms. In the second P3- site, P3- is bonded in a 9-coordinate geometry to three Sm2+ and six Ni1+ atoms. In the third P3- site, P3- is bonded in a 9-coordinate geometry to four Sm2+ and five Ni1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(Ni2P)2 by Materials Project

ErNi4P2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Er is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.80 Å) and four longer (2.83 Å) Er–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.30 Å) and one longer (2.31 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Er and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Ni2P)2 by Materials Project

YNi4P2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Y is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.80 Å) and four longer (2.85 Å) Y–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.30 Å) and one longer (2.32 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Y and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Applicability of the Delplot method for the determination of catalytic reaction sequences: Hydrodeoxygenation of $\gamma$-valerolactone on Ni 2 P/MCM-41

Contact-time measurements based on sites are used to investigate the reaction sequence of the hydrodeoxygenation of γ-valerolactone (GVL) on Ni 2 P/MCM-41. Here the study is carried out at 300 °C and 0.5 MPa with site times of 0.29–6.1 s. A reaction network is proposed in which pentanoic acid and 2-methyltetrahydrofuran (2-MTHF) are formed in parallel initially and pentanal, butane and pentane are formed subsequently. A first-rank Delplot analysis (selectivity) gives a good fit, but higher-rank Delplots do not. The lack of applicability is explained by the magnitude of the rate constants, in which the rate constant for one of the later steps (the consumption of pentanal) is substantially larger than those for the preceding steps. For this reason, pentanal demonstrated the characteristics of a primary product and consequently affected the discrimination of higher rank products. A simulation of a model sequence with assumed rate constants confirms the reason why the Delplot method does not work for this reaction. Since the rate constants cannot be determined a priori to be of close magnitude, the Delplot method cannot be generally used to ascertain reaction sequences.

42 ENGINEERING↗
DOE OSTI2025

Facet-Dependent Hydrogen Evolution Reaction on M 2 P (M = Ni, Co, Fe) Single Crystals

Transition-metal phosphides (MPs) are promising earth-abundant catalysts for hydrogen evolution reactions (HERs) due to their remarkable activity and stability. To further improve their properties, facet control is a key strategy. The growth of shape-selected nanoparticles may substantially enhance electrocatalytic activity, but this approach requires fundamental studies of facet-specific catalytic properties. There are only a few reports on the facet effects of MPs, which leads to a limited understanding of the activity of each facet and hampers catalyst design. Here, in this study, we grew large hexagonal-prism-shaped single crystals of three representative M 2 P (M = Ni, Co, and Fe) catalysts using metal flux routes. Two facets of M 2 P single crystals were tested to study facet-dependent HER activities, and it was consistently demonstrated that for all M 2 P crystals, a tip facet [(0001) for Ni 2 P/Fe 2 P and (010) for Co 2 P] had a higher activity than the side facet [(101̅0) for Ni 2 P/Fe 2 P and (100) for Co 2 P]. HER activity between the same facet elucidated the activity ordered between different transition metals as Fe 2 P > Co 2 P > Ni 2 P under low-potential regions. At high applied potentials, this trend is reversed due to the differences in Tafel slopes, with Ni 2 P becoming the most active catalyst, such that the activity of the (0001) facet of Ni 2 P approaches that of Pt. The calculated surface density of states (DOS) of each facet and its local curvature were found to be a useful descriptor for the activity trends among different transition metals of the same facets.

Co2P↗
DOE OSTI2020

Mild and Selective Hydrogenation of Nitrate to Ammonia in the Absence of Noble Metals

Motivated by increased awareness about nitrate contamination of surface waters and its deleterious effects in human and animal health, we sought an alternative, non-noble metal catalyst for the chemical degradation of nitrate. First row transition metal phosphides recently emerged as excellent alternatives for hydrogen evolution and hydrotreating reactions. We demonstrate that a key member of this family, Ni 2 P, readily hydrogenates nitrate (NO 3 – ) to ammonia (NH 3 ) near ambient conditions with very high selectivity (96%). One of the few non-precious metal-based catalysts for this transformation, and among ca. 1% of catalysts with NH 3 selectivity, Ni 2 P can be recycled multiple times with limited loss of activity. Both nitrite (NO 2 – ) and nitric oxide (NO) intermediates are also hydrogenated. Density functional theory (DFT) indicates that—in the absence of a catalyst—nitrite hydrogenation is the reaction bottleneck. A variety of adsorbates (H, O, N, NO) induce surface reconstruction with top-layer Ni-rich surface stoichiometry. Critically, H saturation coverage on Ni 2 P(001) is only ca. 3 nm –2 , significantly less than that on Pd(111) and Ni(111) of ca. 15–18 nm –2 , which may play a key role in allowing coadsorption of NO x – . Here the ability of Earth-abundant, binary metal phosphides such as Ni 2 P to catalyze nitrate hydrogenation could transform and help us to better understand the basic science behind catalytic hydrogenation and, in turn, advance the next generation of oxyanion removal technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗