(621bs) Design of {100}-Terminated Bimetallic Electrocatalysts for CO2 Reduction to C2 Species

Authors: 
Ma, X., Virginia Polytechnic Institute and State University
Xin, H., Virginia Polytechnic Institute and State University

Electrochemical reduction of carbon dioxide (CO2) on metal electrodes has attracted increasing interest in recent years not only for the sustainable production of fuels and commodity chemicals but also as a means of mitigating greenhouse gas emissions  [1,2]. Among transition and post-transition metals, coinage metals (Cu, Ag, and Au) show pronounced activities for CO2 reduction owing to their moderate affinities toward molecules and their fragments, i.e., adsorbing CO2 and its derived intermediates strongly to break required chemical bonds and weakly enough for those species to be further reduced to carbon monoxide (CO), hydrocarbons, or oxygenates  [3,4] . This reaction is known to be sensitive to surface structure of the catalysts. For example, Cu (111) facets and steps can reduce CO2 to methane (CH4) with Faradaic efficiency up to 46%, albeit requiring very high overpotentials (~1.0 V). In contrast, Cu(100) electrodes displays a comparable selectivity toward more valuable C2 species, e.g., ethylene (C2H4), at somewhat lower overpotentials (~0.8 V)  [5–7]. While controlling the surface structure of metal nanoparticles with high fraction of {100} facets for CO2 electroreduction proves to be fruitful, further improvements in energy efficiency and selectivity to C2 products are needed for the implement of this technology.

In this regard, bimetallic catalysts have shown great promise for several technologically important reactions. By exploiting the synergy of metallic species alloyed, surface sites with novel physicochemical properties can be designed. However, it is very time-consuming and costly to search for highly optimized alloy materials by experimental trial-and-error. Herein we tackle this challenge by identifying descriptive and easily computable parameters (termed descriptor) for CO2 reduction to C2 species on {100}-terminated bimetallic electrocatalysts. To facilitate the computational screening, we extend the standard d-band model, developed by Hammer and Nørskov in 1990s, to Cu and other coinage metal alloys for large-scale exploration of DFT calculated descriptors in bimetallic materials space.

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