Exploring the Remarkable Heterogeneity of Bimetallic Alloy Facet Reactivity for the Electrocatalytic Reduction of CO2

Bimetallic alloys alloy make promising catalysts due to heterogenous active sites that allow small molecule adsorbates to be stabilized compared to single-metal active sites. The number of possible active sites for such intermetallics is much larger than for single-metal catalysts due to the compositional design space and the much larger number of possible facets resulting from a loss of some crystal symmetries. Screens that have worked for single-metal systems, such as systematically identifying activity for 111 or 211 metal facets, fail to capture the most exciting active sites for these alloys. We demonstrate this challenge for the case of nickel/gallium alloy catalysts, which have shown experimental reactivity for the electrocatalytic reduction of CO2. Using DFT, we show that the limiting potential for the rate-limiting step of CO hydrogenation can vary by approximately 1eV over alloy composition and facet, and that alloys can demonstrate a number of possible sites with interesting stabilization. We use the insights from this systematic study to develop rules and methods to make exploring future bimetallic alloys more computationally efficient in light of this large design space.