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Controlling the charge transfer pathway in semiconductors is an important method to improve charge separation efficiency and enhance photoelectrochemical activity. In this work, a Fe2O3/FePO4/FeOOH nanorod photoanode with stepped energy band structure is prepared by a hydrothermal and water bath method. The charge separation efficiency of the ternary heterojunction is higher than that of the traditional type II heterojunction, which might be due to the efficient cascade charge transfer and separation effect of the ternary stepped energy band heterojunction. The H2 and O2 evolution rates for photoelectrochemical water splitting of Fe2O3/FePO4/FeOOH photoanode are 0.247 and 0.111 μmol min−1, which is 2.15 and 1.95 times that of the Fe2O3/FePO4 photoanode, respectively. The incident photocurrent efficiency (IPCE) of Fe2O3/FePO4/FeOOH photoanode under 365 nm light irradiation is 1.5 and 1.8 times that of Fe2O3/FePO4 and Fe2O3/FeOOH photoanodes, respectively. This work provides an attractive strategy for solar energy conversion to construct efficient photoelectrochemical photoanode materials.

Graphitic carbon nitride (g-C3N4) usually shows a low photoelectrochemical (PEC) performance due to its poor conductivity. To improve the transfer of charge carriers generated by g-C3N4, a TiO2/g-C3N4 composite photoanode was prepared by a facile co-electrodeposition method. The composite photoelectrodes exhibit an improved PEC performance compared to TiO2 and g-C3N4. The PEC performance was optimized by varying the mass ratio of TiO2 to g-C3N4, and a ratio of 1:1 gave the best photocurrent density of 1.81 mA cm−2, which is 2.27 times larger than that of the pure TiO2 photoanode under full-arc xenon light. Furthermore, compared with pure g-C3N4, the photocurrent density is greatly improved. The incident photocurrent efficiency reached 4.14% under irradiation with 365 nm monochromatic light. TiO2/g-C3N4 exhibits a stable photocurrent density in a PEC reaction over 2 h. The enhanced PEC performance is attributed to the synergism between TiO2 and g-C3N4 semiconductors, which improves the interfacial charge transfer and inhibits the photogenerated electron–hole pair recombination.

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