Computational screening of silver-based single-atom alloys catalysts for CO2 reduction.

Abstract

Electrocatalytically reducing CO2 into value-added products is a challenging but promising process. Catalysts have been proposed to reduce the potential necessary for the reaction to occur, among which single-atom alloys (SAAs) are particularly promising. Here, we employ density functional theory calculations and the computational electrode model to predict whether silver-based SAAs have the potential to be effective electrocatalysts to convert CO2 into C1 products. We take into account surface defects by using the Ag(211) surface as a model. We also verify whether the proposed materials are prone to OH poisoning or enhance the competing hydrogen evolution reaction. Our calculations predict that these materials show weak mixing between the host and the dopant, characterized by a sharp peak in the density of states near the Fermi energy, except when copper (also a coinage metal) is used as the dopant. This affects the adsorption energy of the different intermediate molecules, yielding different reaction profiles for each substrate. As non-doped silver, copper-doped SAA tends to spontaneously desorb carbon monoxide (CO) instead of proceeding with its reduction. Other elements of the fourth period (Fe, Co, and Ni) tend to bind to the CO molecule but do not favor more reduced products. These metals also tend to enhance the hydrogen evolution reaction. On the contrary, we show that the Ir and Rh dopants have significant potential as electrocatalysts, which favors the reduction of CO over its desorption while also suppressing the hydrogen evolution reaction at potentials lower than those required by copper. They have also been shown to not be prone to poisoning by OH radicals.