Polyoxometalate‐Based Au–Ag Alloy Nanocatalysts for Efficient Electrochemical CO 2 Reduction Reaction

ABSTRACT The electrochemical CO 2 reduction reaction (CO 2 RR) to carbon monoxide (CO) offers a promising strategy for mitigating global warming while providing a valuable industrial feedstock. Polyoxometalates (POMs), anionic metal–oxo clusters, are attractive precursors for CO 2 RR catalysts owing to their structural and compositional tunability, as well as their versatility of their countercations. However, POM‐based CO 2 RR catalysts often exhibit limited activity and require high overpotentials. Herein, we report a high performance CO 2 RR nanocatalyst derived from a Ba 2+ salt of an Au–Ag alloy nanocluster incorporated in a POM framework, [Au 8 Ag 26 (P 8 W 48 O 184 )] 24− ( AuAg ), supported on a carbon black (Ba‐ AuAg /C). This system achieves a high current density (171 ± 4 mA cm −2 ) and Faradaic efficiency (95.3 ± 4.2%) for CO production at a low overpotential (−0.39 V RHE ), outperforming previously reported POM‐based CO 2 RR catalysts. Postreaction analyses reveal the transformation of Ba‐ AuAg /C into small Au–Ag alloy nanoparticles with uniform elemental distribution, along with WO x nanoaggregates. Control experiments and detailed characterizations highlight the critical roles of the constituent elements, countercations, and catalyst structure in achieving superior catalytic performance. This work provides a new design strategy for the development of highly efficient and selective POM‐based nanocatalysts for electrochemical CO 2 conversion.