Efficient photocatalytic hydrogen evolution over graphdiyne boosted with a cobalt sulfide formed S-scheme heterojunction

Graphdiyne (GDY, g-CnH2n–2), a novel two-dimensional carbon hybrid material, has attracted significant attention owing to its unique and excellent properties. As a new type of carbon material, GDY has a layered structure and can be used in the field of photocatalytic water splitting. Therefore, herein, new progress in the preparation of graphene using CuI powder as a catalytic material and the combination of a facile hydrothermal method to prepare a new composite material, Co9S8-GDY-CuI, is reported. The hydrogen production activity of Co9S8-GDY-CuI in the sensitization system reached 1411.82 μmol g–1 h–1, which is 10.29 times that of pure GDY. A series of characterization techniques were used to provide evidence for the successful preparation of the material and its superior photocatalytic activity. Raman spectroscopy showed that the material contains acetylenic bonds, and the X-ray photoelectron spectroscopy carbon fitting peaks indicated the presence of C–C(sp2) and C–C(sp), further demonstrating that GDY was successfully prepared. A possible reaction mechanism was proposed by making use of UV-visible diffuse reflectance and Mott-Schottky analyses. The results showed that a double S-scheme heterojunction was constructed between the samples, which effectively accelerated the separation and transfer of electrons. In addition, the introduction of Co9S8 nanoparticles greatly improved the visible light absorption capacity of Co9S8-GDY-CuI. Photoluminescence spectroscopy and related electrochemical characterization further proved that recombination of the electron-hole pairs in the composite material was effectively suppressed.