Enhanced photoelectrochemical water splitting on heterostructured α-Fe2O3-TiO2:X (X = Co, Cu, Bi) photoanodes: Role of metal doping on charge carrier dynamics improvement

Hematite is a strategical material for photoelectrochemical (PEC) water splitting due to their abundance, stability, non-toxicity, and outstanding electrical and optical properties. However, its limited charge transfer has been challenging towards solar energy conversion. In this work, we show an efficient and novel strategy to improve the charge transfer of hematite photoanode by the formation of a heterostructure with doped TiO2 using metal transition ions (X = Co, Cu, Bi). The results indicated that the PEC water splitting performance of the α-Fe2O3-TiO2:X photoanodes were improved according to Bi > Cu > Co metal ions. The photoconversion efficiency was increased 5.5 times in the Bi-doped sample, along with an increment in the charge separation efficiency of 2.5 times. This improvement was related to the charge carrier dynamics: a high visible light absorption, low recombination, and efficient charge separation. EIS analysis showed a higher donor density in the doped samples, which implies a high carrier concentration and conductivity, improving the electron-hole transport efficiency of the photoelectrochemical performance.