Heterostructured Hematite Photoanodes featuring C₃N₄ with In-Situ Grown Ni-CoP_x for Boosted Photoelectrochemical Water Oxidation

The high demand for renewable and clean energy resources has led to the rapid development of cutting-edge materials for photoelectrochemical (PEC) water splitting. However, the question of how to enhance solar conversion efficiency remains a persistent challenge. In line with this, we present a novel constructive strategy for a ternary-material-system photoanode, aimed at simultaneously improving charge separation and transfer, as well as water oxidation efficiency. Specifically, we demonstrate the PEC efficiency of composite Ti-Fe₂O₃/CN/NCP photoanodes obtained by loading hierarchical C₃N₄ (CN) nanosheets anchored with in-situ grown Ni-doped CoP_x (NCP) onto porous Ti-doped hematite (Ti-Fe₂O₃) photoanodes. The resulting Ti-Fe₂O₃/CN/NCP photoanodes exhibit a remarkable enhancement of photocurrent density (2.01 mA cm⁻² at +1.23 V_RHE) compared to Ti-Fe₂O₃ photoanodes (0.28 mA cm⁻² at +1.23 V_RHE). It is noteworthy that CN and NCP serve to deplete photogenerated electrons and remove photogenerated holes directionally from the surface of Ti-Fe₂O₃. This leads to the facile transfer and separation of electron-hole pairs necessary for exceptional catalytic performance. Moreover, we undertake a systematic analysis of the role of CN and NCP to gain deeper insights into the underlying mechanisms for the superior PEC water oxidation process.