Co3O4@SnO2/graphdiyne type-II heterojunction and p-n heterojunction jointly enhance photocatalytic hydrogen production: Co-O-Sn bond as a bridge for electron transfer

Graphdiyne is a new two-dimensional carbon allotrope material with a two-site lattice co-hybridized by sp(2) and sp. Graphdiyne has a single-layer two-dimensional planar structure. Compared with graphene with zero band gap, graphdiyne has a band gap, inherent semiconductor characteristics, and excellent physical and chemical properties. In this study, we used a Prussian blue analogue (CoCo-PBA) as a precursor to form Co3O4 by calcination. Co3O4 containing a SnO2 shell was synthesized by calcining CoCo-PBA adsorbed with Sn4+. A Co-O-Sn bond was formed between the contact surfaces of SnO2 and Co3O4 as a fast transfer channel of photogenerated electrons. The ternary catalyst Co3O4@SnO2/graphdiyne (CSG) was constructed by combining Co3O4 with graphdiyne. Through high temperature calcination, the three components are intimately fused, and the resulting heterojunction enlarges the contact area and active sites, which is beneficial to the faster transfer of photogenerated carriers. The hydrogen production of the composite catalyst was as high as 113.63 mu mol in 5 hours, which was 51.66 times that of GDY and 6 times that of Co3O4. The in situ XPS shows the transfer direction of photogenerated electrons of the composite catalyst under visible light. In this study, a composite catalyst CSG-1.5 was derived from Prussian blue analogues, which maintained the strong redox ability of the photogenerated electron and hole pairs and more effectively promoted the transport of charge. It provides a new idea and possibility for the application of graphdiyne-based photocatalysts in water splitting to produce hydrogen.