Tunable surface modification of a hematite photoanode by a Co(salen)-based cocatalyst for boosting photoelectrochemical performance

Abstract

In this work, a water splitting photoanode composed of hematite (α-Fe₂O₃) nanorods was modified with a Co(salen)-based cocatalyst, which was proven to exhibit special photoelectrochemical (PEC) oxygen evolution activity. Co(salen) was deposited on the surface of the α-Fe₂O₃ photoanode as a precursor of the cocatalyst and then heat-treated at different temperatures. When the annealing temperature is 250 °C, Co(salen) transforms into Co³⁺ species stabilized with C–N ligands, which act as active sites and decrease the OER energy barrier for the photoelectrochemical process of the α-Fe₂O₃ photoanode. Meanwhile, the interaction between Co–C–N and Fe (Co–C–N⋯Fe) via van der Waals force can provide a photocarrier transfer pathway to achieve a 1.7 fold higher photocurrent at 1.23 V vs. RHE and 180 mV onset potential negative shift compared to those of the pure α-Fe₂O₃ photoanode. This work demonstrates a unique surface structure of a cocatalyst created by a post synthetic strategy using a metal complex precursor containing organic ligands.