2D/2D Cu-tetrahydroxyquinone MOF/N-doped graphene heterojunction as photocatalyst for overall water splitting

A novel 2D/2D heterojunction (CuTHQ/NG) has been prepared by in situ growth of the 2D CuTHQ MOF on defective N-doped graphene (NG), and its photocatalytic activity for overall water splitting studied in detail. CuTHQ/NG heterojunction has demonstrated better photocatalytic activity (480 mu mol/g) than the individual components (257 and 65 mu mol/g for CuTHQ and NG, respectively) for H2 evolution. Furthermore, unlike the individual components, the as-prepared 2D/2D CuTHQ/NG heterojunction promotes overall water splitting under simulated sunlight (164 mu mol of H2/g and 80 mu mol of O2/g). We have also studied the photo-induced charge separation and recombination reactions. Photocurrent measurements and emission quenching experiments have confirmed improved charge separation in the CuTHQ/NG heterojunction. Moreover, the charge recombination kinetics have been investigated with transient absorption spectroscopy. Electron/hole recombination in the heterojunction has been determined more than one order of magnitude slower (8.9 mu s) than the mechanical mixture of CuTHQ and NG (0.35 mu s). Finally, the photochemical stability of the 2D/2D heterojunction has been investigated performing a long-term (96 h) experiment, demonstrating near linear H2 evolution along the irradiation time. (c) 2022 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).