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The construction of semiconductor heterojunctions is regarded as an efficient strategy for promoting photogenerated carrier transfer and enhancing photocatalytic performance. [1] Moreover, the in-situ self-assembly method of the main catalyst and the cocatalyst is believed to overcome the shortcomings of the traditional surface loading method and provide a more efficient hydrogen evolution reaction capability. In this work, Zn-Cd-Mo-S quaternary metal sulfide mesoporous nanospheres were generated by in-situ self-assembly via a one-step mild hydrothermal method. A photocatalyst with a double-heterojunction synergistic structure and a large specific surface area was constructed to form a high-speed charge transfer channel as a mechanism to promote photocatalytic hydrogen production. The best quaternary catalyst ZCM 5 S has a hydrogen evolution yield of 23.32 mmol h−1 g−1, which is 53 times and 11 times that of the corresponding binary (CdS) and ternary (ZnCdS) metal sulfides, respectively, and still has high stability within 20 h. Furthermore, the ZCM 5 S gets an apparent quantum efficiency (AQE) of 6.9 % at 420 nm. Through further analysis, such as photoluminescence (PL) and photoelectrochemical, etc., the enhanced photocatalytic performance of ZCM 5 S can be attributed to the synergistic effect of the heterojunction between ZnS and CdS and the heterojunction between ZnCdS and MoS 2. In addition, the Pt-like structure of molybdenum sulfide cocatalyst can lead to efficient photoinduced charge separation and transfer. Meanwhile, the mesoporous structure endows the material with abundant reactive sites and increases the catalytic reaction efficiency. The unique in situ construction method of this work also provides a reference for the design and synthesis of heterojunction quaternary catalysts for green energy conversion. [Display omitted] • The mesoporous structure increases the reactive site area. • The double heterojunction synergy facilitates exciton transfer. • Quaternary sulfides outperform their parent materials. • A method for in situ syntheses of quaternary metal sulfides is proposed. • The main and co-catalyst one-step method is beneficial and feasible. [ABSTRACT FROM AUTHOR]

• Ag nanoparticles are anchored onto CuS sub-micron flowers to form composites. • The CuS@Ag electrodes exhibit enhanced charge storage property. • The decoration of Ag nanoparticles increases the electrical conductivity. • The generated electric field at the CuS/Ag interface accelerates the charge transfer. [Display omitted] In this reported work, Ag nanoparticles (NPs) decorated CuS sub-micron flowers are synthesized using a facile, solvothermal reaction coupled with a silver mirror reaction. The experimental results and theoretical calculations reveal that decorating the CuS with Ag NPs increases its intrinsic electrical conductivity and generates an electric field at the interface between Ag and CuS. These effects promote the efficient utilization of active materials and accelerate the interface charge transfer and electrochemical reaction kinetics. Consequently, the maximum specific capacity of the prepared CuS@Ag electrodes is found to be as high as 702 C g−1 at 2 A g−1, which is about 5 times greater than the pure CuS electrode. In addition, the capacity value is 400 C g−1 at 20 A g−1 and it exhibits 93% retention of the initial capacity after 5000 cycles at 10 A g−1. Moreover, a hybrid supercapacitor (HSC) device is assembled employing the CuS@Ag electrode as the positive electrode, which delivers an energy density of 51.1 Wh kg−1 at a power density of 798 W kg−1. These results demonstrate the promising potential of the fabricated CuS@Ag composites for further application in HSCs. [ABSTRACT FROM AUTHOR]