BiVO4/Fe2O3/ZnFe2O4; triple heterojunction for an enhanced PEC performance for hydrogen generation

n/n/n triple heterojunction photoanodes made up of Zr:W-BiVO4, Fe2O3, and ZnFe2O4 metal oxides are fabricated through a simplistic spray pyrolysis method. Use of Zr and W as dopants in BiVO4 plays an important role as Zr increases the carrier density and W reduces the charge recombination. Further, Fe2O3 and ZnFe2O4 serve as a protective layer for Zr:W-BiVO4, which augmented the photoelectrochemical performance and achieved a 1.90% conversion efficiency in the triple heterojunction. XRD measurements display the crystalline nature and reduction in particle size due to strain in the sample, UV-vis absorbance shows an extended absorption towards the visible region and the FE-SEM imaging confirms the successful deposition of ZnFe2O4 over BiVO4/Fe2O3. By analyzing the band edge position, it was observed that on formation, the triple heterojunction not only suppresses the charge carrier recombination but also utilizes the band edge offset for the water splitting reaction using solar energy.