Electrolyte effects on undoped and Mo-doped BiVO4 film for photoelectrochemical water splitting

Particle-Based Photoelectrodes for PEC Water Splitting: Concepts and Perspectives

This comprehensive review delves into the intricacies of the photoelectrochemical (PEC) water splitting process, specifically focusing on the design, fabrication, and optimization of particle-based photoelectrodes for efficient green hydrogen production. These photoelectrodes, composed of semiconductor materials, potentially harness light energy and generate charge carriers, driving water oxidation and reduction reactions. The versatility of particle-based photoelectrodes as a platform for investigating and enhancing various semiconductor candidates is explored, particularly the emerging complex oxides with compelling charge transfer properties. However, the challenges presented by many factors influencing the performance and stability of these photoelectrodes, including particle size, shape, composition, morphology, surface modification, and electrode configuration, are highlighted. The review introduces the fundamental principles of semiconductor photoelectrodes for PEC water splitting, presents an exhaustive overview of different synthesis methods for semiconductor powders and their assembly into photoelectrodes, and discusses recent advances and challenges in photoelectrode material development. It concludes by offering promising strategies for improving photoelectrode performance and stability, such as the adoption of novel architectures and heterojunctions.

Nanoporous Ta3N5via electrochemical anodization followed by nitridation for solar water oxidation

Nanoporous tantalum nitride (Ta3N5) is a promising visible-light-driven photoanode for photoelectrochemical (PEC) water splitting with a narrow band gap of approximately 2.0 eV. It can utilize a large portion of the solar spectrum up to 600 nm to improve the activity of photooxidation reactions because of enhanced light scattering and an overall increase of the surface area with high light absorption and carrier collection. Herein, we synthesized a new n-type nanoporous tantalum nitride film on Ta foil by electrochemical anodization with a fluorinated electrolyte. Post-annealing in a nitrogen/ammonia mixture gas environment then transformed amorphous TaOx to crystalline Ta3N5. Effects of annealing temperature on the microstructure, optical properties, and PEC properties of samples were then investigated under changeable stoichiometry of Ta and N elements in the Ta-based nitride film. Results showed that the film annealed at 1000 °C showed high crystallinity, high visible light absorption, and a highly conductive interlayer between the substrates, resulting in the highest photocurrent density (JSC) of ∼0.25 mA cm-2 at 1.23 VRHE in PEC water splitting. In addition, depending on the annealing temperature, it is possible to engineer band alignment in the nanoporous Ta3N5 layer, allowing a beneficial charge transfer process.