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Bismuth ferrite (BiFeO 3) holds great potentials in the photoelectrocatalysis due to the advantages of low cost, narrow band gap and good chemical stability. However, the photoelectrochemical performance of BiFeO 3 is usually inhibited by the poor charge carrier transport. Here, we report the flame annealing synthesized Sm3+ doped BiFeO 3 photocathodes for efficient hydrogen production. Greatly enhanced water reduction activity was found in doped samples. The Bi 0.95 Sm 0.05 FeO 3 composition exhibited largest photocurrent density of 0.1061 mA cm−2 at 0 V vs. RHE in 0.5 M Na 2 SO 4 , which was 5.6 times higher than that of the pristine BiFeO 3. Mott-Schottky analysis and electrochemical impedance spectra proved that the Bi3+substitution increased the charge carrier concentration and facilitated the charge migration. Incident photon-to-electron conversion efficiency (IPCE) value for Bi 0.95 Sm 0.05 FeO 3 film (∼6.39% at 325 nm) was approximately ten times higher than that of undoped sample. The high performance can be ascribed to the rational Sm3+ doping, which can improve visible light absorption ability, facilitate the charge carrier transport kinetics and hinder the recombination of photogenerated carriers. Our work provides a facile cation doping with rare earth ions to improve the photoelectrochemical performances. [ABSTRACT FROM AUTHOR]