Hydrophilic bi-functional B-doped g-C₃N₄ hierarchical architecture for excellent photocatalytic H₂O₂ production and photoelectrochemical water splitting

Graphitic carbon nitride (g-C₃N₄) has attracted great interest in photocatalysis and photoelectrocatalysis. However, their poor hydrophilicity poses a great challenge for their applications in aqueous environment. Here, we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C₃N₄ nanoplatelets. Such hierarchical B-doped g-C₃N₄ material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium, leading to an excellent photocatalytic H₂O₂ production rate of 4240.3 μM g⁻¹ h⁻¹, 2.84, 2.64 and 2.13 times higher than that of the bulk g-C₃N₄, g-C₃N₄ nanoplatelets and bulk B doped g-C₃N₄, respectively. Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 mA cm⁻² at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting. This work makes a fundamental improvement towards large-scale exploitation of highly active, hydrophilic and stable metal-free g-C₃N₄ photocatalysts for various practical applications.