Development of a photoelectrochemically self-improving Si/GaN photocathode for efficient and durable H2 production

Development of efficient yet durable photoelectrodes is of paramount importance for deployment of solar-fuel production. The photoelectrochemically self-improving behaviour of a silicon/gallium nitride photocathode highly efficient for hydrogen production is now reported. Development of an efficient yet durable photoelectrode is of paramount importance for deployment of solar-fuel production. Here, we report the photoelectrochemically self-improving behaviour of a silicon/gallium nitride photocathode active for hydrogen production with a Faradaic efficiency approaching similar to 100%. By using a correlative approach based on different spectroscopic and microscopic techniques, as well as density functional theory calculations, we provide a mechanistic understanding of the chemical transformation that is the origin of the self-improving behaviour. A thin layer of gallium oxynitride forms on the side walls of the gallium nitride grains, via a partial oxygen substitution at nitrogen sites, and displays a higher density of catalytic sites for the hydrogen-evolving reaction. This work demonstrates that the chemical transformation of gallium nitride into gallium oxynitride leads to sustained operation and enhanced catalytic activity, thus showing promise for oxynitride layers as protective catalytic coatings for hydrogen evolution.

Automated summary

Efficient and durable photoelectrodes are crucial for solar-fuel production. A silicon/gallium nitride photocathode was found to exhibit self-improving behavior for hydrogen production. By forming a gallium oxynitride layer, the catalytic activity of the photocathode was enhanced, leading to sustained operation and improved performance.