A chemist's guide to photoelectrode development for water splitting – the importance of molecular precursor design

Abstract

Photoelectrochemical (PEC) water splitting is a promising method for generating green hydrogen as a solar fuel, overcoming the issues associated with unreliability and periodicity of renewable technologies. While research in this field is growing, there is a distinct gap between complex device development and fundamental synthesis of the individual materials. For optimal device fabrication we need materials scientists and engineers to create complex multicomponent photoelectrodes, but also inorganic chemists to design bespoke precursors tailored to produce highly efficient, specifically designed photoelectrode materials. The success of precursor design for semiconductors in fields such as microelectronics has proven the significant impact of the precursor, however, this approach has yet to be used extensively in device fabrication for PEC water splitting. This review acts as a guide towards bespoke precursor development for the fabrication of tailored thin films; particularly how to design the structure and composition of the precursor to promote and enhance the most desired properties, including solubility, volatility, and thermal decomposition. The key areas of focus for device design are outlined, including both single thin film performance and overall device modifications and additions to create a high-performance PEC water splitting electrode. There is a specific emphasis towards chemical vapour deposition techniques due to the suitability for scale-up and commercial application compared to alternatives, and importantly, the significant influence of the molecular precursor on the deposition, and hence its link to synthetic chemistry. We aim to direct more synthetic chemists towards the field of PEC water splitting, encouraging collaboration to connect these two areas and bring the target of a commercially and industrially viable PEC system ever closer.