Enhanced Hydrogen Production via Surface Oxygen Vacancy Regulation in Element-Doped Ni/CeO2 Catalysts

Abstract Steam reforming of methane (SRM) for H2 production is a critically important industrial H2 production pathway that has attracted extensive research. However, catalyst deactivation and instability at high reaction temperatures and low water-to-methane ratios remain pressing challenges. Herein, we constructed Ni metal catalysts supported on ceria doped with different elements (Pr, Sm, La, Tb, Zr). By regulating the concentration of surface oxygen vacancies, nickel dispersion, and the strength of metal–support interaction, highly efficient methane steam reforming for H2 production was achieved. Optimized Pr-doped ceria-supported Ni catalysts achieved a methane conversion rate of 56.8%, H2 selectivity of 46.6%, and an absolute H2 production rate of 936.62 mmol/gcat·h at 650 °C. XRD results confirmed successful incorporation of elements into the ceria lattice, enhancing Ni metal dispersion. HRTEM revealed that the Pr-doped Ni metal particle size decreased from 21 nm (undoped) to 17 nm, indicating significantly improved Ni metal dispersion. XPS analysis revealed a substantial increase in oxygen vacancy concentration on the catalyst surface after elemental doping, particularly for Pr-doped samples where the oxygen vacancy concentration rose to 42.9%. The characterization of spent catalysts demonstrated that elemental doping suppressed sintering of both ceria and metal phases, attributed to enhanced metal–support interactions mediated by oxygen vacancies induced by doping.