Decreased Surface Photovoltage of ZnO Photoanode Films via Optimal Annealing Temperature for Enhanced Photoelectrochemical Performance

The electronic structure of semiconducting materials at the electrode/electrolyte interface plays a vital role in the process of photoelectrochemical (PEC) water splitting. In this work, we could reliably tune the surface defect density of ZnO films through changing the annealing temperature, thereby optimizing the PEC performance. The surface photovoltage (SPV) of ZnO films could be obtained by Kelvin probe force microscopy and compared to insightfully understand the effect of the annealing temperature on the performance of the electrode in PEC water splitting. The minimum SPV annealed at 450 degrees C indicated low surface defect density, eventually resulting in an enhanced photoelectrochemical performance. The applied bias photo-to-current efficiency of ZnO films annealed at 450 degrees C reached 0.237%, about 7.4 times that of unannealed ZnO photoanode. This work provides an effective method for the rational fabrication of efficient photoelectrodes for the realization of high-performance photoelectrochemical water splitting.