Integration of cobalt-phosphate catalyst and titanium dioxide interlayer in the hematite photoanodes to improve photoelectrochemical water splitting for hydrogen production

Photoelectrochemical water splitting (PEC-WS) is an environmentally benign technology for hydrogen generation. Hematite (α-Fe₂O₃) photoanodes have received extensive attention in PEC-WS field due to their high absorption coefficient and suitable bandgap, but suffer from severe carrier recombination at surfaces and interfaces and poor kinetics of oxygen evolution reaction. The α-Fe₂O₃ photoanode, built by coupling of the electron transport layer as interface energetics and surface catalyst, can improve the PEC-WS performance through combining the advantages of diverse active sites and synergy effect. Herein, α-Fe₂O₃ photoanodes, integrated with the electron transport layer of titanium dioxide (TiO₂) and surface catalyst of cobalt-phosphate (Co-Pi), exhibit an excellent long-term stability up to 10 h, a significant enhancement over 100% in the photocurrent at 1.23 V_RHE and a remark cathodic shift of 210 mV in the onset potential. On account of analyzing the carrier-transport kinetic, the significant PEC-WS improvement can be ascribed to the fact that the TiO₂ and Co-Pi synergistically enhance the photogenerated-carrier separation and transfer efficiencies. The main role of Co-Pi catalyst is to decrease surface recombination rate. In addition, heterojunctions formed on the interface and surface can further promote photogenerated-carrier separation. This work provides a state-of-the-art strategy for surface and interface engineering to boost the carrier extraction and hydrogen production efficiency in photoelectric conversion field. Graphical Abstract: [Figure not available: see fulltext.]