TiO2/graphene/NiFe-layered double hydroxide nanorod array photoanodes for efficient photoelectrochemical water splitting

Abstract

The ever-increasing demand for renewable and clean power sources has triggered the development of novel materials for photoelectrochemical (PEC) water splitting, but how to improve the solar conversion efficiency remains a big challenge. In this work, we report a conceptual strategy in a ternary material system to simultaneously enhance the charge separation and water oxidation efficiency of photoanodes by introducing reduced graphite oxide (rGO) and NiFe-layered double hydroxide (LDH) on TiO₂ nanorod arrays (NAs). An experimental–computational combination study reveals that rGO with a high work function and superior electron mobility accepts photogenerated electrons from TiO₂ and enables fast electron transportation; while NiFe-LDH acts as a cocatalyst which accelerates the surface water oxidation reaction. This synergistic effect in this ternary TiO₂/rGO/NiFe-LDH photoanode gives rise to a largely enhanced photoconversion efficiency (0.58% at 0.13 V) and photocurrent density (1.74 mA cm⁻² at 0.6 V). It is worth mentioning that the photocurrent density of TiO₂/rGO/NiFe-LDH, to the best of our knowledge, is superior to previously reported TiO₂-based photoanodes in benign and neutral media. In addition, the method presented here can be extended to the preparation of other efficient photoanodes (WO₃/rGO/NiFe-LDH and α-Fe₂O₃/rGO/NiFe-LDH) toward high level PEC performance.