Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media
Artikel i vetenskaplig tidskrift, 2023

Ag-based catalysts have recently attracted much attentionas potentialcandidates to substitute costly Pt-based electrocatalysts for theoxygen reduction reaction (ORR) in alkaline media. Although the electrocatalyticactivity of Pt-based alloys is known to exhibit a strong dependenceon their electronic structures, a relationship between electronicstructure and the ORR mechanism in Ag-based alloys still remains tobe elucidated. Herein, by means of physical vapor deposition, we prepareAg binary thin films (CoAg, CuAg, AuAg, and FeAg) with well-controlledcompositions as a tool to investigate the ORR mechanism on Ag surfaces.The bimetallic thin films are evaluated for their ORR performancein alkaline media, and their specific activity at 0.8 V-RHE is shown to correlate with the Ag electronic structure. Even thoughall thin films show different responses to potential cycling, allbimetallic samples exhibit a surface Ag enrichment after ORR. It isshown that the ORR occurs through different mechanisms on these Ag-richsurfaces, which in turn is potential-dependent. Tafel slopes revealfaster ORR kinetics at low overpotentials on all surfaces, whereasonly CuAg surpasses pure Ag at higher overpotentials. Moreover, despitetheir incomplete O-2 reduction, CuAg and AuAg exhibit anoverall superior ORR activity over pure Ag, with a more than 2-foldincrease in specific activity at 0.8 V-RHE attributed toenhancements originating from electronic effects and surface defects,respectively. Since the potential-dependent improved ORR mechanismobserved for Ag bimetallic samples makes a rational design of Ag-basedelectrocatalysts difficult, these results aim to provide insightsfor a more tailored design of electrocatalysts by shedding light onthe mechanisms through which the ORR kinetics are improved on Ag surfacesin alkaline media.

oxygen reduction reaction

alkaline fuel cells

physical vapordeposition

thin films




Gerard Montserrat Siso

Chalmers, Fysik, Kemisk fysik

Björn Wickman

Chalmers, Fysik, Kemisk fysik

ACS Applied Energy Materials

25740962 (eISSN)

Vol. 6 12 6428-6442

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