Facile solvothermal assisted g-C3N4 post-grafting with aromatic amine dyes for effective photocatalytic hydrogen evolution†
Abstract
A facile solvothermal assisted g-C3N4 post-grafting technique with aromatic amine dyes via a Schiff base chemical reaction was successfully developed in this study. Based on this strategy, three D–π–A type aromatic amine organic dyes (TPA-CNCHO, PTZ-CNCHO, and CZ-CNCHO) were covalently grafted onto g-C3N4. The resulting composite photocatalyst was characterized using TEM, XPS, FT-IR, UV-Vis DRS, PL, and transient photocurrents, which confirmed the feasibility of the modification strategy. The values for the photocatalytic hydrogen production rates obtained for g-C3N4/TPA-CNCHO, g-C3N4/PTZ-CNCHO, and g-C3N4/CZ-CNCHO were 16232.7, 13266.9, and 11822.8 μmol h−1 g−1 respectively. Each of these values is 40, 33, and 29 times higher than that of pure g-C3N4, respectively. Among them, g-C3N4/TPA-CNCHO exhibited the highest photocatalytic hydrogen-production activity and the highest recycling usage stability. In addition, a possible mechanism for the separation and transfer of photo-induced carriers was obtained based on DFT calculations and experimental results. This further confirmed that covalently post-grafting g-C3N4 with organic aromatic amine dyes through a Schiff base reaction was useful and could effectively enhance the photocatalytic hydrogen evolution reaction. This is a general facile solvothermal method because it can be used for the grafting of other types of functional aromatic organic dyes onto g-C3N4.