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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Unsupported and carbon-supported silver catalysts for oxygen reduction reaction in alkaline media

Quick and easy Ag catalysts preparation via wet chemical synthesis method using only reducing agent (pure-Ag); reducing agent and citric acid as the capping agent (Ag-CA); and carbon support (KetjenBlack 600J), capping agent, and the reducing agent (Ag/C) is demonstrated. The Ag-based electrocatalysts are characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of Ag catalysts for O 2 reduction reaction (ORR) in 1 M KOH is evaluated using the rotating (ring)-disc electrode method. SEM and HAADF-STEM results show that the unsupported pure-Ag and Ag-CA catalysts consist mainly of big agglomerates, and Ag/C has the smallest agglomerates and some sub-3 nm Ag nanoparticles. The XPS results reveal that Ag in all the catalysts is in the metallic form (Ag 0 ). Despite consisting of big agglomerates, the Ag-CA catalyst exhibits similar ORR electrocatalytic activity to that of Ag/C. Ag-CA (unsupported) shows the lowest hydrogen peroxide yield. These results are of great importance for the development of Ag-based catalysts that can be prepared in a fast, simple and easily up scalable fashion, for anion exchange membrane fuel cells.

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

Materials Data on CaAg2 by Materials Project

Ag2Ca crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ca is bonded in a 12-coordinate geometry to twelve equivalent Ag atoms. There are a spread of Ca–Ag bond distances ranging from 3.27–3.51 Å. Ag is bonded in a 10-coordinate geometry to six equivalent Ca and four equivalent Ag atoms. There are three shorter (2.78 Å) and one longer (2.93 Å) Ag–Ag bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2Ag7 by Materials Project

Ag7Ca2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to fourteen Ag atoms. There are a spread of Ca–Ag bond distances ranging from 3.22–3.42 Å. There are three inequivalent Ag sites. In the first Ag site, Ag is bonded to four equivalent Ca and eight Ag atoms to form a mixture of face, edge, and corner-sharing AgCa4Ag8 cuboctahedra. There are a spread of Ag–Ag bond distances ranging from 2.78–2.94 Å. In the second Ag site, Ag is bonded to four equivalent Ca and eight Ag atoms to form a mixture of face, edge, and corner-sharing AgCa4Ag8 cuboctahedra. There are a spread of Ag–Ag bond distances ranging from 2.79–2.96 Å. In the third Ag site, Ag is bonded in a 12-coordinate geometry to four equivalent Ca and eight Ag atoms. There are a spread of Ag–Ag bond distances ranging from 2.86–3.23 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca5Ag3 by Materials Project

Ag3Ca5 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded to five Ag atoms to form a mixture of distorted edge, corner, and face-sharing CaAg5 trigonal bipyramids. There are a spread of Ca–Ag bond distances ranging from 3.19–3.37 Å. In the second Ca site, Ca is bonded in a distorted square co-planar geometry to six Ag atoms. There are four shorter (3.16 Å) and two longer (3.74 Å) Ca–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 10-coordinate geometry to ten Ca atoms. In the second Ag site, Ag is bonded in a 9-coordinate geometry to eight Ca and one Ag atom. The Ag–Ag bond length is 2.88 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaAg by Materials Project

AgCa crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ca is bonded in a 7-coordinate geometry to seven equivalent Ag atoms. There are a spread of Ca–Ag bond distances ranging from 3.20–3.22 Å. Ag is bonded in a 9-coordinate geometry to seven equivalent Ca and two equivalent Ag atoms. Both Ag–Ag bond lengths are 2.91 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3Ag8 by Materials Project

Ca3Ag8 crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Ca is bonded in a 12-coordinate geometry to twelve Ag atoms. There are a spread of Ca–Ag bond distances ranging from 3.15–3.56 Å. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 2-coordinate geometry to four equivalent Ca and eight Ag atoms. There are a spread of Ag–Ag bond distances ranging from 2.84–3.14 Å. In the second Ag site, Ag is bonded to six equivalent Ca and six equivalent Ag atoms to form a mixture of face and corner-sharing AgCa6Ag6 cuboctahedra.

36 MATERIALS SCIENCE↗