Mg-Doped CuFeO2 Photocathodes for Photoelectrochemical Reduction of Carbon Dioxide

Mg-doped CuFeO2 delafossite is reported to be photoelectrochemically active for CO2 reduction. The material was prepared via conventional solid-state methods, and subsequently assembled into an electrode as a pressed pellet. Addition of a Mg2+ dopant is found to substantially improve the conductivity of the material, with 0.05% Mg-doped CuFeO2 electrodes displaying photocathodic currents under visible irradiation. Photocurrent is found to onset at irradiation wavelengths of similar to 800 nm with the incident photon-to-current efficiency reaching a value of 14% at 340 nrn using an applied electrode potential of -0.4 V vs SCE. Photoelectrodes were determined to have a -1.1 V vs SCE conduction band edge and were found capable of the reduction of CO2 to formate at 400 mV of underpotential. The conversion efficiency is maximized at -0.9 V vs SCE, with H-2 production contributing as a considerable side reaction. These results highlight the potential to produce Mg-doped p-type metal oxide photocathodes with a band structure tuned to optimize CO2 reduction.