Photoelectrochemical (PEC) water splitting has been regarded as an ideal strategy to solve the current energy crisis and realize net-zero carbon dioxide emissions, and the key for an efficient PEC process is highly active photoanode catalysts. Herein, we developed a simple hydrothermal-calcination approach to fabricate Fe2O3 nanorods (NRs) doped with Ni2+, Ca2+, and Mg2+, respectively, which exhibited improved PEC performance than bare Fe2O3 NRs. The experimental results indicate that Ni2+, Ca2+, and Mg2+ were successfully doped into the lattice of Fe2O3, which can change the electronic structure of α-Fe2O3 and thus increase the density of charge carriers and reduce charge transfer resistance. Meanwhile, abundant oxygen vacancies were induced simultaneously with the Mg-doping process, which realize the synergy promotion of elemental doping and oxygen vacancies. Therefore, the optimized Mg-doped Fe2O3 NRs exhibited the highest photocurrent density of 0.763 mA·cm–2, which is 4.86-fold higher than that of the pure Fe2O3 NRs. This work indicates that the synergy of elemental doping and oxygen vacancies is an effective approach to improve the PEC performance of Fe2O3 NRs.

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