Integration of element codoping and electron-donor functional groups into metal–organic framework to improve photoelectrochemical water oxidation of hematite photoanode

Abstract

Hematite (α-Fe₂O₃) can be a promising photoelectrode to promote the development of photoelectrochemical water splitting (PEC-WS), but the low photogenerated carrier separation efficiency limits the further application. In this work, a nano-heterojunction is constructed by a metal–organic framework (MOF-5) and α-Fe₂O₃ films to regulate photogenerated carrier transport. The electronic structure regulation (element doping and electron-donor functional groups) is introduced to solve the problems of poor electrical conductivity of MOF-5 and interface defects and band mismatch caused by contacting with α-Fe₂O₃ film. The α-Fe₂O₃/NH₂:MOF-5(Ni)@Ru photoanode exhibits the optimal photocurrent density of 2.6 mA/cm² at 1.23 V_RHE, which is 2.68 times of the pure α-Fe₂O₃ photoanode. This can be attributed to that the introduction of MOF catalyst can provide more abundant active sites for PEC water oxidation. The element codoping and synergistic effect of Ni and Ru improve the conductivity and inhibit the recombination rate of photogenerated electron–hole pairs of α-Fe₂O₃ photoanode. The electron-donor functional group of –NH₂ can regulate the electron distribution to prolong the lifetime of photogenerated holes, which further enhances the photogenerated carrier separation and transfer efficiency.