Insight into the High Efficiency of Cu/CeO2(1 1 0) Catalysts for Preferential Oxidation of CO from Hydrogen Rich Fuel

•Synthesized CuO/CeO2(110) catalysts show excellent performance for PROX with best Con. 100% and Sel. 99.8% at 90 °C;•Quasi in-situ XPS and HS-LEIS, as well as CO-IR, evidence the dispersion of Cu+ under reaction condition;•Cu+/CeO2 plays the main role for CO oxidation;•Cu0 appears concurrently with the initiation of hydrogen oxidation during PROX reaction;•To stabilize Cu+ on CeO2 is the key to achieve high catalytic performance for PROX;