Efficient photocatalytic hydrogen evolution reaction promoted via a synergistic strategy of S-scheme heterojunction structure combined with surface plasmon resonance effect

Photocatalysis has great potential for the utilization of solar energy, which depends on the design and preparation of an efficient photocatalyst. The recent design of S-scheme heterojunction is expected to enhance the redox ability and accelerate electron separation and migration. To further promote the charge transfer and broaden light absorption in the heterostructure, we proposed a strategic merging with the surface plasmon resonance (SPR) effect. In this work, the (C and O) co-doped g-C3N4 (COCN) was in-situ combined with W18O49 to construct the S-scheme heterojunction termed COCN-W18O49. Co-doping of C and O atoms leads to a change in the band structure of COCN, the formation of surface defects, and an enhancement in carriers concentration. The W18O49 possesses plentiful W5+ defects and oxygen vacancies, which can produce hot electrons to accelerate the separation of carriers and broaden the wavelength range of light absorption by the SPR effect. Furthermore, the S-scheme heterojunction effectively utilizes the reduction and oxidation units of COCN and W18O49, respectively, and the presence of an internal electric field with direction from COCN to W18O49 accelerates electron transfer. As a result, the novel S-scheme COCN-W18O49 heterojunction can achieve a superior photocatalytic degradation performance that is 4.25 times as high as GCN, 2.3 times as high as COCN, and 1.6 times as high as W18O49. At the same time, the hydrogen evolution performance of the COCN-W18O49 composite was also 11.9 times as high as GCN and 1.8 times as high as COCN, while W18O49 was unable to hydrogen evolution. This work provides a new pathway for designing S-scheme heterojunction with swift interfacial electron flows, which has great potential for hydrogen evolution and wastewater treatment applications.