A three-dimensional graphitic carbon nitride belt network for enhanced visible light photocatalytic hydrogen evolution

Abstract

Three-dimensional (3D) network-like graphitic carbon nitride nanobelts (g-C₃N₄ NBs) were facilely achieved by the hydrothermal treatment of bulk g-C₃N₄ in a medium strong oxalic acid solution (1 M, pH 0.89). The positions of the conduction band (CB) and valence band (VB) were upraised from −0.90 and +1.86 eV for bulk g-C₃N₄ to −0.92 and +1.92 eV for g-C₃N₄ NB networks with enhanced redox ability, respectively. With an optimized Pt loading of 3%, the g-C₃N₄ NB networks showed excellent visible-light photocatalytic H₂ production activity (1360 μmol g⁻¹ h⁻¹), which was 10.9 times higher than that of optimized 2% Pt@bulk g-C₃N₄ (124.7 μmol g⁻¹ h⁻¹) using triethanolamine as a sacrificial agent. Furthermore, Pt@g-C₃N₄ NBs exhibited a considerable rate of H₂ evolution of 33.3 μmol g⁻¹ h⁻¹, much higher than 1.79 μmol g⁻¹ h⁻¹ for Pt@bulk g-C₃N₄ in distilled water without any sacrificial agents, revealing a great potential for photocatalytic overall water splitting. This outstanding performance not only originates from its unique 3D nanostructure and prolonged electron lifetime, but also from the electronic structure modulation and improved redox capacities of the CB and VB. The pH effect of hydrothermal conditions on the g-C₃N₄ molecular structure, chemical elements, optical properties and catalytic performance is also expounded. This study demonstrates a facile and environmentally friendly strategy to design highly efficient g-C₃N₄ catalysts for potential applications in solar energy driven photocatalytic water splitting.