Dendritic CuBi₂O₄ Array Photocathode Coated with Conformal TiO₂ Protection Layer for Efficient and Stable Photoelectrochemical Hydrogen Evolution Reaction

Abstract

Short carrier diffusion length and poor photostability are two major bottlenecks limiting the application of CuBi2O4 as a competitive candidate for photoelectrochemical (PEC) hydrogen evolution reaction (HER). To overcome the bottlenecks, we develop a novel template-assisted synthesis strategy to prepare the CuBi2O4 dendrites and then protect the dendritic structure with a conformal nanometer-thick TiO2 passivation layer. The obtained CuBi2O4/TiO2 composite dendrites exhibit high activity for the PEC HER with a photocurrent density of ca. 0.90 mA cm–2 at 0.200 V vs reversible hydrogen electrode (RHE) in neutral solution, and this value is among the highest reported on CuBi2O4-based photocathodes at the same potential. Moreover, the CuBi2O4/TiO2 dendrites show a high photostability with the photocurrent density being stabilized at ca. 0.36 mA cm–2 (88.8% of its original value) after 6 h measurements at a high applied potential of 0.600 V vs RHE, which is superior to all CuBi2O4-based photocathodes reported recently in the literature. This work provides an effective strategy to improve the activity and stability of the copper-oxide-based materials for the HER via constructing a dendritic structure and protecting the structure with a nanoscale TiO2 passivation layer.