A Red Light-Inducible Copper-Photodeposited All-Solid-State Z-Scheme Photocatalyst for Carbon Dioxide Reduction to Methane Using Water as an Electron Donor

We selectively loaded various amounts of copper (Cu)as a cocatalystfor the reduction reaction onto zinc rhodium oxide (ZnRh2O4 (ZRO)) in a heterojunction photocatalyst and silver(Ag)-inserted ZRO and bismuth vanadium oxide (Bi4V2O11 (BVO)) solid-state photocatalyst (ZRO/Ag/BVO(ZAB)) to form Cu/ZAB. The amount of deposited Cu was controlled bythe photodeposition time to generate Cu/ZAB with up to 0.14 wt % Cucocatalyst vs ZAB. All the prepared Cu/ZAB samples accomplished overallwater splitting under red light irradiation at a wavelength of 700nm, enhancing the stoichiometric evolutions of hydrogen and oxygenfrom water compared with bare ZAB. Moreover, the apparent quantumefficiency increased up to 0.13 wt % Cu cocatalyst, which thereaftertended to decrease. The optimized Cu/ZAB photocatalyst was confirmedto reduce carbon dioxide (CO2) to methane using water asan electron donor and proton source under irradiation with visiblelight at a wavelength of 700 nm, which is, to our knowledge, the longestwavelength reported to date for CO2 reduction.