Hematite Homojunction Constructed with Ti, Cu, and S Doping for Solar Water Splitting

Hematite (α-Fe2O3) has a high theoretical photocurrent but has not achieved much due to its sluggish water oxidation kinetics and severe charge recombination. In the present work, gradient Cu and S doping was introduced into Ti-doped Fe2O3 (Ti:Fe2O3) through a high-temperature diffusion process at 450 °C from the doping source of CuSO4. The Ti-, Cu-, and S-doped Cu@Ti:Fe2O3 photoanode, without cocatalyst modification, obtains a high photocurrent density of 1.81 mA cm–2 at 1.23 VRHE under AM 1.5G illumination. Compared with Fe2O3, the onset potential of Cu@Ti:Fe2O3 shifts significantly negatively by around 520 mV. The improvement should be mainly attributed to the formed p–n homojunction, which can provide extra energy for the separation of charges that are generated by light. Interestingly, the photocurrent density can increase gradually during the stability test under illumination and reach a photocurrent density of 2.45 mA cm–2 after 10 h. This can be ascribed to surface dissolution of the Cu@Ti:Fe2O3 photoanode, which induces more active sites and obvious characteristics of the p–n homojunction.