Sustainable Production of Layered Bismuth Oxyhalides for Photocatalytic H2 Production

Bismuth oxyhalides (BiaObXc X = Cl, Br, I) are promising layered photocatalysts that can produce H2 using solar light. The layered crystal structures minimize electron-hole recombinations in these materials and provide compositional flexibilities that allow for band gap tuning. Current literature highlights developments in synthetic routes and improved performance metrics; however, an analysis of the sustainability of these compounds is missing. In this Perspective, we use the life cycle assessment framework as a guide to evaluate the sustainability of each stage of the bismuth oxyhalide life cycle, from raw material extraction (mining, refinement, purification) all the way through the end of the material's life and consider ways to recycle and/or reuse the spent photocatalyst. Here, we gather and unite information from the bismuth oxyhalide field with information from the sustainability literature in the first attempt to evaluate the sustainabilities of these materials as photocatalysts for H2 production. We present our own perspective on the future of the field and make recommendations for researchers interested in this class of materials and photocatalysts more broadly.