Fabrication of efficient CuS/BiVO4 p-n heterojunctions for sensing and photo-reduction of Cr (VI)

•CuS /BiVO4 composites are formed by hydrothermal synthesis at 100 °C for 16 h by keeping different molar ratio (1:1, 1:2, and 2:1).•The n-type and p-type semiconducting behavior of BiVO4 and CuS prove the composite as a best candidate for both sensing of Cr (VI) to 99 % and increased the photo reduction efficiency towards Cr (VI) to 98 %.•The reducibility nature of the composite is beneficial for sustainability. Applications in sensing and photo reduction of Cr (VI) by pristine BiVO4 are restricted because of the narrow band gap and easy electron-hole recombination. To overcome the issue, CuS is coupled to BiVO4indifferent molar ratios (1:1, 1:2, and 2:1) by hydrothermal synthesis and used in Cr (VI) sensing and photo-reduction. The tetragonal zircon phase of BiVO4 and hexagonal structure of CuS have been confirmed through XRD. Then n-type and p-type behavior of BiVO4 and CuS respectively have been shown from a Mott-Schotky study. The Current–Voltage characteristics of all the samples were found to be linear and ohmic in nature. The conduction and valence band position of BiVO4 (+0.33 eVand +3.08 eV) and CuS (-0.30 eV and +1.81 eV) ensures the development of p-n heterojunction and channelization of the photo-induced charge carriers. This helps in decreasing electron-hole recombination, thereby increasing the sensing efficiency (99%) and photo-reduction (98%) of Cr (VI) at a concentration of 40 ppm. [Display omitted] Schematic Diagram of Detection and Photo-Reduction of Cr (VI) using CuS /BiVO4 Composite.