A recyclable molten-salt synthesis of B and K co-doped g-C3N4 for photocatalysis of overall water vapor splitting

Abstract Photocatalytic overall water splitting is one of the green and efficient energy technologies. Due to difficult release of O2 from photocatalysts, the simultaneous generation of H2 and O2 is a critical challenge for water splitting. B and K co-doped g-C3N4 (B/K-g-C3N4) catalyst was synthesized by the recyclable molten-salt method in this study. Compared with the K doped and pristine g-C3N4 samples, B/K-g-C3N4 exhibited the highest photocatalytic activity for water vapor splitting under visible light illumination. The yield ratio of H2 and O2 reached approximately 2:1, and the corresponding rates were 1.18 and 0.58 μmol/h after 24 h of illumination. The B/K-g-C3N4 sample demonstrated good photocatalytic stability after 9 cycles. Additionally, the co-doped g-C3N4 catalyst, obtained from the repeatedly recyclable salts, still exhibited equivalent photocatalytic activity. Based on the built structure model with g-C3N4, the HOMO and LUMO distributions were changed by B and K co-doping, leading to improved separation of photoinduced carriers. The photocatalytic mechanism for water splitting over g-C3N4 semiconductor was speculated.