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 BiVO 4 are restricted because of the narrow band gap and easy electron-hole recombination. To overcome the issue, CuS is coupled to BiVO 4 indifferent 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 BiVO 4 and hexagonal structure of CuS have been confirmed through XRD. Then n-type and p-type behavior of BiVO 4 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 BiVO 4 (+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. Schematic Diagram of Detection and Photo-Reduction of Cr (VI) using CuS /BiVO4 Composite.