Mg-Doped CuFeO₂ Photocathodes for Photoelectrochemical Reduction of Carbon Dioxide

Abstract

Mg-doped CuFeO 2 delafossite is reported to be photoelectrochemically active for CO 2 reduction. The material was prepared via conventional solid-state methods, and subsequently assembled into an electrode as a pressed pellet. Addition of a Mg 2+ dopant is found to substantially improve the conductivity of the material, with 0.05% Mg-doped CuFeO 2 electrodes displaying photocathodic currents under visible irradiation. Photocurrent is found to onset at irradiation wavelengths of ∼800 nm with the incident photon-to-current efficiency reaching a value of 14% at 340 nm 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 CO 2 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 CO 2 reduction.

Light-Driven Heterogeneous Reduction of Carbon Dioxide: Photocatalysts and Photoelectrodes

“…Gu et al reported that the Mg-doped delafossite CuFeO 2 can act as a photoelectrocatalyst under illumination of <800 nm light. 233 Although this system can be used to reduce CO 2 to formate at an underpotential of approximately 400 mV, the Faradaic efficiencies are generally poor, with a maximum efficiency of 10% at −0.9 V vs SCE.…”

Recent progress on advanced design for photoelectrochemical reduction of CO2 to fuels

“…In 2013, a Mg-doped CuFeO 2 delafossite photocathode was fabricated to achieve the PEC reduction of CO 2 to formate [95]. The Mg 2+ dopant extended the absorption of visiblelight and improved the conductivity of photocathode, offering an FE of 10% at −0.9 V versus SCE and an incident photon-to-current efficiency (IPCE) value of 14% at 340 nm using an applied potential of −0.4 V versus SCE.…”

Photoelectrochemical production of useful fuels from carbon dioxide on a polypyrrole-coated p-ZnTe photocathode under visible light irradiation

“…30 The conduction band edges could be calculated by subtracting the measured band gaps from the valence band edges. Flat band potential (V f ) can be calculated by subtracting k B T/e from the x-intercept in the linear plot of 1/C 2 vs V. The negative slope of Mott-Schottky plots means the p-type property of semiconductor and vice versa.…”