Exploring new single, active photocatalysts for solar-water splitting is highly desirable to expedite current research on solar-chemical energy conversion. In particular, Z-scheme-based composites (ZBCs) have attracted extensive attention due to their unique charge transfer pathway, broader redox range, and stronger redox power compared to conventional heterostructures. In the present report, we have for the first time explored CuP, a new, single photocatalyst for solar-water splitting applications. Moreover, a novel ZBC system composed of BiWO-CuP was designed employing a simple method of ball-milling complexation. The synthesized materials were examined and further investigated through various microscopic, spectroscopic, and surface area characterization methods, which have confirmed the successful hybridization between BiWO and CuP and the formation of a ZBC system that shows the ideal position of energy levels for solar-water splitting. Notably, the ZBC composed of BiWO-CuP is a mediator- and co-catalyst-free photocatalyst system. The improved photocatalytic efficiency obtained with this system compared to other ZBC systems assisted by mediators and co-catalysts establishes the critical importance of interfacial solid-solid contact and the well-balanced position of energy levels for solar-water splitting. The promising solar-water splitting under optimum composition conditions highlighted the relationship between effective charge separation and composition.

Varied morphologies and compositions of bismuth tungstate nanocomposites have been investigated as promising materials for photocatalytic applications. Among these nanocomposites, hierarchically structured bismuth sulphide (Bi 2 S 3 )/bismuth tungstate (Bi 2 WO 6 ) hybrids have significant photocatalytic efficiency toward heavy metal ions. In order to simplify the synthetic procedure for this desirable composite, we developed a robust single-step hydrothermal synthesis for the formation of hierarchically structured hetero-catalysts of Bi 2 S 3 /Bi 2 WO 6 with a high yield (>95%). The synthesized heterostructures were characterized by various spectroscopic, microscopic, and surface area analysis techniques, which confirmed the successful incorporation of Bi 2 S 3 into the Bi 2 WO 6 matrix and were used to optimize pore size for enhanced catalytic activity. The resulting Bi 2 S 3 /Bi 2 WO 6 heterocatalysts were used to remove toxic Cr(VI) ions via reduction to water insoluble Cr(III) utilizing visible-light irradiation. We also investigated the role of citric acid as a hole scavenger in the reduction of Cr(VI) with minimizing the rate of electron-hole recombination during photocatalysis. Likewise, the observed catalytic activity was significantly enhanced under a condition of an appropriate balance between hierarchical structure of catalysts and the amount of hole scavenger. ASSOCIATED CONTENT Supporting informationAdditional information about FESEM images of Bi 2 WO 6 synthesized under different conditions, comparative XPS of Bi 4f and W 4f, BET surface area and BJH pore size distribution, digital photograph of Cr(VI) reduction to Cr(III) along with effect of CA on Cr(VI) reduction in dark, energy level diagram of composite. This material is available free of charge via internet at