Improving Stability and Photoelectrochemical Performance of BiVO4 Photoanodes in Basic Media by Adding a ZnFe2O4 Layer

BiVO4 photoanodes have mainly been investigated under neutral conditions because BiVO4 gradually dissolves under extreme pH conditions. In this study, the possibility of utilizing ZnFe2O4 as a protection layer to stabilize BiVO4 in a 0.1 M KOH solution was investigated. A 10-15 nm thick ZnFe2O4 layer was conformally placed on a nanoporous BiVO4 electrode by photodepositing a FeOOH layer, followed by drop casting a zinc nitrate solution and annealing. The resulting BiVO4/ZnFe2O4 electrode generated a photocurrent density of >2 mA/cm(2) at 1.23 V versus RHE with a significantly improved stability compared with the pristine BiVO4 electrode. The incident and absorbed photon-to-current conversion efficiencies along with absorption spectra suggested that the ZnFe2O4 protection layer also contributes to photocurrent generation by increasing photon absorption and electron hole separation. These results suggest that further investigation of protection and catalyst layers can enable more stable and efficient operation of BiVO4-based photoanodes in basic media.