Carbon-Coated Cu nanoparticles as a Cocatalyst of g-C₃N₄ for Enhanced Photocatalytic H₂ Evolution Activity under Visible-Light Irradiation

The photocatalytic H₂ evolution is an important technology to solve the energy crisis. The hydrogen evolution rate of the graphite carbon nitride (g-C₃N₄) system in triethanolamine solution as sacrificial agent is clearly higher than that in methanol solution. But up to now, most of the Cu nanoparticles as cocatalyst of g-C₃N₄ photocatalytic systems for hydrogen evolution are performed in methanol solution because Cu nanoparticles are unstable in triethanolamine solution. Here, carbon-coated Cu nanoparticles as a cocatalyst of g-C₃N₄ composites (Cu@C/g-C₃N₄) are prepared by a simple two-step technology that includes annealing followed by grinding. The compositions, morphology, and optical and photoelectrochemical properties of the composites are characterized by means of physicochemical techniques. The prepared composition is used to generate hydrogen under visible-light irradiation in triethanolamine solution. The results show that the hydrogen evolution rate of the optimal Cu@C/g-C₃N₄ is up to 265.1 μmol g⁻¹ h⁻¹, which is close to the activity of 0.5% Pt/g-C₃N₄, and after four repeated reactions, the photocatalytic activity decreases only by ≈15%. The good photocatalytic activity and stability result from Cu nanoparticles increase the transfer efficiency of charge carriers by trapping the photogenerated electrons produced by g-C₃N₄ and the protective effect of carbon layer on Cu nanoparticles.