Rapid and recyclable photocatalytic reduction of hexavalent chromium ions over copper oxide-decorated hydrothermally-prepared tungsten trioxide nanorods under visible-light

Photoreduction of heavy metals over semiconductor nanostructures is a capable technique for saving the environment and health. As a result, plentiful research proposals ranged from designing photocatalysts to realize their application. The solution's stability and reproducibility is another crucial factor for the sustainability of the designed photocatalysts. In this work, a mixed soft template-aided solvothermal route with an ultrasonic seeding method is performed to grow tungsten trioxide (WO3) nanorods, followed by coupling copper oxide (CuO) over their surface to construct CuO/WO3 heterojunctions. The synthesized photocatalysts displayed an enhanced visible-light absorbance owing to the CuO incidence at 4.0 to 20.0 wt% and bandgap decrease to 2.15 eV compared with 2.84 eV in parent WO3. The obtained mesoporous texture was not significantly affected by adding CuO with a surface area ranging from 169 to 225 m2g−1. The prepared photocatalysts were applied for the reduction of hexavalent chromium ion (Cr(VI)) to the less toxic trivalent one (Cr(III)). The 1.6 gL−1 of 16 % CuO/WO3 has reduced Cr(VI) to Cr(III) at a rate of 265.33 μmol min−1. In addition, CuO/WO3 heterostructured photocatalyst has signified five-time reused stability. This superb activity is accredited to the S-scheme charge transfer by the synergetic effect of precise CuO amount and enhanced visible-light harvesting.