Catalytic Activity and Product Selectivity Trends for Carbon Dioxide Electroreduction on Transition Metal-Coated Tungsten Carbides

Abstract

Electrochemical reduction of CO2 is a promising technology to produce hydrocarbon and alcohol fuels in a carbon neutral cycle. To utilize the technology on a commercial scale, inexpensive and earth-abundant catalysts are needed. Here, we employ density functional theory calculations to investigate activity and product selectivity trends for CO2 electroreduction reaction on transition metal monolayer coated tungsten carbides, M/WC (M = Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Ir, Pt, and Au). Such core–shell systems have the potential to reduce the loading of precious metals, such as Ag and Au, while the catalytic properties for CO2-to-CO reduction of metal surfaces remain. We find that at low potentials (<0.5 V) Cu/WC and Pd/WC core–shell particles catalyze CO2 reduction to CO as the main product due to low COOH formation and CO desorption free energies. Furthermore, we show that the binding energies of the carbo- and oxo-intermediates on the M/WC catalyst surface obey scaling relations with the binding energies of CO and O, respectively. The binding energies of these two key intermediates exhibit linear relationships with the total d-band center of the surface metals; thus, the d-band center can be utilized as a unified electronic-structure-based descriptor to predict the product selectivity. Such a unified descriptor is useful for efficient screening for improved core–shell catalysts. This work illustrates the potential of core–shell metal/metal-carbide particles as a platform for the design of inexpensive CO2 electroreduction catalysts.