Engineering the interfaces in water-splitting photoelectrodes-an overview of the technique development

Photoelectrochemical (PEC) water splitting offers an attractive option for solar fuel production to solve the global energy crisis and environmental issues, but the present low efficiency hinders its practical application. Interface engineering has been demonstrated to be critical for developing high-performance photoelectrodes for efficient water splitting. However, effective interface engineering requires insightful understanding of the interfacial thermodynamics, carrier dynamics, and surface reaction mechanisms, all of which essentially depend on the advances of study techniques. Herein, electrochemical and optical spectroscopic techniques applied for interface studies in PEC systems are overviewed. The fundamentals and data analysis methods of each technique are introduced, in company with representative achievements in understanding the PEC interfaces. Both conventional and newly developed techniques are included, with some discussions on their advantages and limitations. Finally, a perspective on the challenges and the future progress of techniques for PEC interface studies is also given. This review could inspire further technique development and a mechanistic understanding of PEC water splitting.