Boosting the Photoactivity of BiVO 4 Photoanodes by a ZnCoFe-LDH Thin Layer for Water Oxidation

Monoclinic bismuth vanadate (BiVO ) has been used as an efficient photoanode material for photoelectrochemical water oxidation owing to its suitable band gap and nontoxicity. Nevertheless, the practical application of BiVO photoanode has been severely limited by the surface charge recombination and sluggish kinetic, which leads to the obtained photoactivity of BiVO is much lower than its theoretical value. In this case, ZnCoFe-LDH thin layer is conformally decorated on the porous BiVO photoanode through a simple electrodeposition process. The results show that a boosted photoactivity and a remarkably enhanced photocurrent density (3.43 mA cm at 1.23 V ) are attained for BiVO /ZnCoFe-LDH. In addition, the optimized BiVO /ZnCoFe-LDH photoanode exhibits significant negative shift in the onset potential (0.51 V to 0.21 V ), promotes charge separation efficiency (49.3% to 60.4% in the bulk, 29.6% to 61.9% on the surface at 1.23 V ) and enhanced IPCE efficiency (25.5% to 54.7% at 425 nm) compared with that of bare BiVO photoanode. It is demonstrated that the boosted photoactivity of BiVO /ZnCoFe-LDH photoanode is mainly ascribed to the synergy effects of the formation of p-n heterojunction between ZnCoFe-LDH and BiVO to accelerate the photogenerated charge transfer and separation, broaden light absorption, as well as promote the surface water oxidation kinetics.