Role of sputtered WO3 underlayer and NiFeCr-LDH co-catalyst in WO3–BiVO4 heterojunction for enhanced photoelectrochemical water oxidation

WO3–BiVO4 (WO-60s/BVO) heterojunction was synthesized by radio-frequency sputtered WO3 onto FTO substrate, followed by spin-coating of BiVO4 layer. Furthermore, Cr incorporated NiFe-LDH (NiFeCr-LDH) oxygen evolution reaction (OER) co-catalyst was electrodeposited onto WO-60s/BVO. The sputtered WO3 underlayer in the WO-60s/BVO facilitated enhanced electron-hole separation and less transient time for the electron to arrive at back contact than conventional spin-coated WO3 layers. Incorporating Cr into NiFe-LDH increased the electrical conductivity of LDH, which resulted in an enhanced transfer of photogenerated charge-carrier and significant promotion of the OER kinetics. The heterojunction with sputtered WO3 underlayer and NiFeCr-LDH co-catalyst attained photocurrent density of 4.9 mA cm−2 at 1.23 V vs. RHE with an IPCE value greater than 56% in the 350–470 nm wavelength range. Moreover, the WO-60s/BVO-NiFeCr photoanode showed only 7% decay in photocurrent after 6 h with H2, and O2 evolution of 98 and 47 μmol cm−2 h, respectively, suggesting high stability for OER.