Water-Stable Boron-Doped Boron Nitride Photocatalyst for Visible Light-Driven H2 Evolution and CO2 Photoreduction

Developing robust, multifunctional photocatalysts that can facilitate both hydrogen evolution via photoreforming of water and gas phase CO2 photoreduction is highly desirable with the long-term vision of integrated photocatalytic setups. Here, we present a new addition to the boron nitride (BN) photocatalyst material platform, boron-doped boron oxynitride (B-BNO), capable of fulfilling this goal. Detailed EPR studies revealed hyperfine interactions between free charges located on discrete OB3 sites, exhibiting an out-of-plane symmetry, and the nuclei of neighbouring boron atoms. This material resolves two long-standing bottlenecks associated to BN-based materials concomitantly: instability in water and lack of photo activity under visible light. We show that B-BNO maintains prolonged stability in water for at least three straight days and can facilitate both liquid phase H2 evolution and gas phase CO2 photoreduction, using UV-Vis and deep visible irradiation (λ > 550 nm), without any cocatalysts. The evolution rates, apparent quantum yields, and selectivities observed for both reactions with B-BNO exceed those of its porous BNO counterpart, P25 TiO2 and bulk g-C3N4. This work provides scope to expand the BN photocatalyst platform to a wider range of reactions.