Synergistic effect of exfoliation and substitutional doping in graphitic carbon nitride for photocatalytic H2O2 production and H2 generation: a comparison and kinetic study

Abstract

Photocatalytic H₂O₂ production and photocatalytic H₂ evolution are regarded as promising technologies since they can achieve sustainable and eco-friendly solar to chemical energy conversion. Herein, exfoliated non-metal doped graphitic carbon nitride photocatalysts were rationally designed for photocatalytic H₂O₂ production and H₂ evolution. The optimised photocatalyst with boron doping and exfoliation exhibited an optimum yield of H₂O₂ up to 398.3 μmol h⁻¹ g⁻¹ and a H₂ evolution rate of 1985 μmol h⁻¹ g⁻¹, which are 8 and 10 fold greater than those of pristine CN, respectively. The enhanced photocatalytic activity can be attributed to effective visible light absorption as identified by UV-vis DRS spectroscopy due to enhanced aromatic π-conjugation, faster charge migration/separation efficiency supported by PL, TRPL and EIS analysis and excellent photostability. Furthermore, the exfoliated boron doped graphitic carbon nitride (e-BCN) nanosheets provide sufficient catalytic sites for oxygen adsorption and also exhibit Lewis acid sites to stabilize the ˙O₂⁻ radical intermediate to prevent the decomposition of H₂O₂. This work not only provides a comparative study of non-metal doping (P, S, B) into the graphitic carbon nitride network and an insightful kinetic study with different affecting parameters for photocatalytic H₂O₂ production but also establishes the groundwork for the formation of highly active photocatalysts for energy and environmental applications.