Abundant Ce3+ Ions in Au-CeOx Nanosheets to Enhance CO2 Electroreduction Performance.

The electroreduction of CO2 to CO provides a potential way to solve the environmental problems caused by excess fossil fuel utilization. Loading transition metals on metal oxides is an efficient strategy for CO2 electroreduction as well as for reducing metal usage. However, it needs a great potential to overcome the energy barrier to increase CO selectivity. This paper describes how 8.7 wt% gold nanoparticles (NPs) loaded on CeOx nanosheets (NSs) with high Ce3+ concentration effectively decrease the overpotential for CO2 electroreduction. The 3.6 nm gold NPs on CeOx NSs containing 47.3% Ce3+ achieve CO faradaic efficiency of 90.1% at -0.5 V in 0.1 m KHCO3 solution. Furthermore, the CO2 electroreduction activity shows a strong relationship with the fractions of Ce3+ on Au-CeOx NSs, which has never been reported. In situ surface-enhanced infrared absorption spectroscopy shows that Au-CeOx NSs with high Ce3+ concentration promote CO2 activation and *COOH formation. Theoretical calculations also indicate that the improved performance is attributed to the enhanced *COOH formation on Au-CeOx NSs with high Ce3+ fraction.