Construction of S-Scheme Co2SnO4/graphdiyne heterojunction to promote carrier transfer for efficiently photocatalytic hydrogen evolution characterized with in situ XPS

Graphdiyne (g-CnH2n-2), a novel two-dimensional carbon isomeric material consisting of a network of sp and sp2 co-hybridized hybridized carbons, has been highly regarded for its excellent chemical and physical properties and unique structure since it was first synthesized in 2010. However, as a photocatalyst, its application in the field of hydrogen production is still rare, which is a good opportunity for the field of photochemical catalyze hydrogen production. In this work, a binary catalyst Co2SnO4/graphdiyne was constructed by calcining graphdiyne and CoSn(OH)6 together after grinding. The structure of high-temperature calcination closely linked Co2SnO4 and graphdiyne, which led to an increased contact area and more active sites with faster photogenerated electron transfer efficiency. Therefore, Co2SnO4/graphdiyne showed good photocatalytic hydrogen production efficiency. Under the optimum amount of EY the hydrogen production rate reached 8.79 mmol g−1 h−1, which was 80.11 and 33.70 times higher than that of Co2SnO4 and graphdiyne, respectively. The construction of Co2SnO4/graphdiyne S-scheme heterojunction proved by in-situ XPS, EPR (DMPO-•O2−) experiment and the hydroxyl radical detection experiment retains high redox potential and prolongs the lifetime of photo-generated carriers. The catalyst preparation method in this work is innovative, which provides a general and high-efficiency strategy for applying the graphdiyne-based S-scheme heterojunction photocatalyst to solar energy-hydrogen energy conversion for photocatalytic water decomposition into hydrogen.