Effect of sulfur doping on photoelectrochemical performance of hematite

Herein, we report preparation of S-doped α-Fe2O3 with enhanced photoelectrochemical water splitting performance, through simply annealing the hematite photoanodes in a furnace containing small amounts of sulfur powder. Characterization results (from XRD, SEM, EDX, UV-vis, FTIR, and XPS) showed successful incorporation of sulfur species into the hematite lattice. Considering obtained results, cationic substitution of sulfur (S4+) in hematite lattice was more probable than its anionic substitution (S2−). In addition, partial reduction of Fe3+ species to Fe2+ followed by increase in oxygen vacancy sites, led to higher charge carrier mobility through polaron hopping mechanism. Higher mobility reduces recombination rate of photo-generated charge carriers in hematite, and as a result, photocurrent produced by the hematite photoanode showed 4 times increase after simple sulfur doping process. The synthesized S-doped hematite is highly stable and shows no performance decline under continuous illumination. Moreover, electrochemical impedance studies indicated that charge transfer at the surface of the photoanode has facilitated after sulfur doping.