Surface chemistry and photoelectrochemistry—Case study on tantalum nitride

Solar water splitting promises a solution to challenges associated with the intermittent nature of solar energy. Of different implementations, photoelectrochemical water splitting, where one or more photoelectrodes harvest light and catalyze water splitting, represents a convenient platform to understand the governing principles of charge behaviors, especially at the light absorber|H2O interface. This Perspective recognizes and discusses the importance of the photoelectrode surface to solar water splitting performance. It presents discussions within the context of a prototypical water splitting material, Ta3N5, which has gained growing attention lately for its outstanding initial performance. Insights into the mechanisms by which Ta3N5 functions are presented, followed by examples of recent efforts to circumvent the issues that Ta3N5 decays rapidly under solar water splitting conditions. Our visions on the future directions of semiconductor-based solar water splitting will be presented at the end.