Construction of Z-scheme Photocatalyst Containing ZnIn2S4, Co3O4-Photodeposited BiVO4 (110) Facets and rGO Electron Mediator for Overall Water Splitting into H2 and O2

Abstract

The self-assemble 0.5Pt-ZnIn2S4/rGO/Co3O4-BiVO4 (110) Z-scheme system photocatalysts were synthesized successfully, in which 0.5Pt-ZnIn2S4, rGO and Co3O4-BiVO4 (110) were as H2-photocatalyst, electron mediator and O2-photocatalyst, respectively. Herein, the preferred exposed (110) crystal facets of BiVO4 have great contribution to optimizing its photocatalytic oxidation performance. The Z-scheme system samples were used for photocatalytic water splitting to H2 and O2 in stoichiometric ratio without any sacrificial agents under visible light irradiation. SEM results clearly revealed the morphology and structure of Pt-ZnIn2S4, rGO and Co3O4-BiVO4 (110), suggesting that the three samples closely contacted with each other. Thus the electrons in the Z-scheme photocatalyst system could flow continuously in the photocatalytic water splitting process, which would induce the highly separation rate of photoinduced charge carriers and then accelerated the photocatalytic performance. Furthermore, rGO and Co3O4 were shown to be the critical factors for the improvment of photoinduced electron–hole pairs, thereby influencing the photocatalytic performance. In 0.5Pt-ZnIn2S4/2rGO/5Co3O4-BiVO4 (110) photocatalyst, the amount of the H2 and O2 could reach 294.3 μmol/g and 143.4 μmol/g, respectively (in 12 h). The mechanism for the photocatalytic overall water splitting was also discussed in detail. We confirmed that Z-scheme 0.5Pt-ZnIn2S4/rGO/Co3O4-BiVO4 (110) exhibit photocatalytic overall water splitting into H2 and O2 (294.3 and 143.4 μmol/g in 12 h). Here, 0.5Pt-ZnIn2S4, rGO and Co3O4-BiVO4 (110) act as H2-photocatalyst, electron-mediator and O2-photocatalyst, respectively. And the contact interface is favourable and then helpful for the electrons flow continuously during the photocatalytic reaction process. The electron mediator rGO and cocatalyst Co3O4 are responsible for the photoactivity.