A series of CaIn2S4-reduced graphene oxide (RGO) nanocomposites with different RGO contents were fabricated using a facile hydrothermal approach. During the hydrothermal process, the reduction of graphene oxide to RGO, in situ deposition of synthesized CaIn2S4 nanoparticles on RGO nanosheets and formation of chemical-bonding CaIn2S4-RGO nanocomposites were performed simultaneously. Under visible light irradiation, the as-prepared CaIn2S4-RGO nanocomposites showed enhanced photocatalytic performance for rhodamine B degradation and phenol oxidation. The sample with 5 wt % RGO hybridized CaIn2S4 exhibited the highest photocatalytic activity. The enhancement of photocatalytic performance may be related to the increased adsorption/reaction sites, positive shift of the valence band potential, and high separation efficiency of photogenerated charge carriers due to the electronic interaction between CaIn2S4 and RGO. We hope that this work can not only provide an in-depth study on the photocatalytic mechanism of RGO-enhanced activity, but also provide some insights for fabricating efficient and stable RGO-based photocatalysts in the potential applications of purifying polluted water resources.Keywords: CaIn2S4; hydrothermal; nanocomposites; reduced graphene oxide; visible-light photocatalysis

A series of CaIn2O4/Fe-TiO2 composite photocatalysts with tunable Fe-TiO2 contents were prepared in which Fe-TiO2 nanoparticles were uniformly deposited onto the surface of CaIn2O4 nanorods. The photocatalytic activities of Pt-loaded CaIn2O4/Fe-TiO2 composites were evaluated for H2 evolution from aqueous KI solution under visible light irradiation. It was found that the composites showed higher H2 evolution rates in comparison with pure CaIn2O4 or Fe-TiO2, which could be attributed to the increased surface area and enhanced visible light absorption. A high H2 evolution rate of 280 μmol h–1 g–1 was achieved when the mass ratio of Fe-TiO2 to CaIn2O4 was 0.5, which was 12.3 and 2.2 times higher than that of pure CaIn2O4 and Fe-TiO2, respectively. Furthermore, the interfaces between CaIn2O4 nanorods and Fe-TiO2 nanoparticles facilitated efficient charge separation that also led to the improved photocatalytic activity. This study may provide some inspiration for the fabrication of visible-light-driven photocatalysts with efficient and stable performance.

A novel ternary sulfide photocatalyst of monoclinic CaIn2S4 with excellent photocatalytic H2 evolution activity is synthesized via a high-temperature sulfurization approach. The precursor orthorhombic CaIn2O4 can be converted in situ to monoclinic CaIn2S4 by using H2S gas as the sulfurization reagent once the sulfurization temperature exceeds 773 K. The obtained yellow powders have a mesoporous structure and a chain-shape morphology with large surface area and high pore volume. SEM and TEM observations indicate that specific nanostep structures are formed on the surface of monoclinic CaIn2S4. Under visible light irradiation, monoclinic CaIn2S4 exhibits considerable performance for photocatalytic hydrogen production. A high H2 evolution rate of 30.2 μmol/h with good stability is achieved from Na2S/Na2SO3 aqueous solution with the deposition of 0.5 wt % Pt nanoparticles, 30 times higher than that of cubic CaIn2S4, which makes it a new promising candidate photocatalyst for hydrogen production. This work can provide an effective approach to the fabrication of other mesoporous sulfide photocatalysts with high performance.