Enhancement of photoelectrochemical performance of BiFeO3 by Sm3+ doping

Bismuth ferrite (BiFeO₃) 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 BiFeO₃ is usually inhibited by the poor charge carrier transport. Here, we report the flame annealing synthesized Sm³⁺ doped BiFeO₃ photocathodes for efficient hydrogen production. Greatly enhanced water reduction activity was found in doped samples. The Bi_0.95Sm_0.05FeO₃ composition exhibited largest photocurrent density of 0.1061 mA cm^?2 at 0 V vs. RHE in 0.5 M Na₂SO₄, which was 5.6 times higher than that of the pristine BiFeO₃. 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_0.95Sm_0.05FeO₃ 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.