Carbon Quantum Dot-Modified and Chloride-Doped Ordered Macroporous Graphitic Carbon Nitride Composites for Hydrogen Evolution

The photocatalytic water-splitting hydrogen evolution technology has the potential to relieve energy crisis and enhance the hydrogen generation efficiency of the catalyst. Herein, a kind of 3DOM-CN composite, which is composed of a three-dimensional ordered macroporous material based on g-C3N4, was synthesized through a colloidal template crystal method. After it was doped with Cl– and modified by carbon quantum dots (CQDs), the as-prepared xCQDs/Cl/3DOM-CN composite showed an evident hydrogen generation ability enhancement irradiated by visible light. The structures, composition, and optical and electrochemical properties of the prepared photocatalysts were comprehensively obtained by transmission electron microscopy (TEM), scanning electron microscopy, high-resolution-TEM, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis, electrochemical impedance spectroscopy, photocurrent, Mott–Schottky, and photoluminescence. The highest hydrogen evolution efficiency under visible-light irradiation was achieved by the 1%CQDs/Cl/3DOM-CN composite with a hydrogen generation rate of 8.12 mmol g–1 h–1, which was nearly five times that of the 3DOM-CN. The photocatalyst exhibited an outstanding stability and reusability after four cycles. Eventually, the mechanism in the process of catalytic hydrogen production was briefly discussed. The synergy of the multiple functions of the CQDs/Cl/3DOM-CN composite offered a technique for enhancing the activity of the photocatalysts in the photocatalytic water-splitting process.