Tuning the product selectivity of CO2/H2O co-electrolysis using CeO2-modified proton-conducting electrolysis cells

Abstract

Co-electrolysis of CO₂ and H₂O to produce fuels using proton-conducting electrolysis cells (PCECs) is a promising technology for effective CO₂ utilization. The direct production of hydrocarbon fuels using PCECs, nevertheless, remains challenging, and the mechanism of CO₂ hydrogenation during electrolysis is still unclear. Here, we demonstrate surface engineering as an effective strategy for promoting the CO₂/H₂O co-electrolysis to produce CH₄ using PCECs. A thin CeO₂ layer is impregnated selectively onto the BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3−δ (BZCYYb) surface of a Ni-BZCYYb fuel electrode. The PCEC with a CeO₂-modified electrode exhibited more than 3 times CH₄ selectivity at 550 °C and 1250 mA cm⁻² than the cell with a pristine electrode. The combination of advanced spectroscopic techniques and density functional theory calculations demonstrates that the decorated CeO₂ modulates the adsorption of reactants and facilitates proton transfer for the hydrogenation process, leading to accelerated CH₄ production. The result provides critical insight into the rational design of high-performance catalysts for other high temperature electrochemical devices.