Tuning the product selectivity of CO/HO co-electrolysis using CeO-modified proton-conducting electrolysis cells

Co-electrolysis of CO 2 and H 2 O to produce fuels using proton-conducting electrolysis cells (PCECs) is a promising technology for effective CO 2 utilization. The direct production of hydrocarbon fuels using PCECs, nevertheless, remains challenging, and the mechanism of CO 2 hydrogenation during electrolysis is still unclear. Here, we demonstrate surface engineering as an effective strategy for promoting the CO 2 /H 2 O co-electrolysis to produce CH 4 using PCECs. A thin CeO 2 layer is impregnated selectively onto the BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3− δ (BZCYYb) surface of a Ni-BZCYYb fuel electrode. The PCEC with a CeO 2 -modified electrode exhibited more than 3 times CH 4 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 CeO 2 modulates the adsorption of reactants and facilitates proton transfer for the hydrogenation process, leading to accelerated CH 4 production. The result provides critical insight into the rational design of high-performance catalysts for other high temperature electrochemical devices. This work demonstrates surface engineering as an effective strategy to modulate the surface adsorption characteristics of reaction intermediates, hence promoting CO 2 /H 2 O co-electrolysis to produce CH 4 using PCECs.