Investigating the interfacial charge transfer between electrodeposited BiVO4 and pulsed laser-deposited Co3O4 p-n junction photoanode in photoelectrocatalytic water splitting

The formation of a p-n junction consisting small-sized, and homogeneous material over the porous semiconductor is an effective strategy for improved photoelectrocatalytic (PEC) water oxidation. Here, the facile pulsed laser deposition (PLD) method was used to load small-sized Co3O4 on BiVO4. The BiVO4/Co3O4 (30 s) photoanode exhibits a higher photocurrent density of 4.66 mA cm−2 @ +1.23 VRHE which is ∼ 4-fold higher than pristine BiVO4. This improved PEC performance is due to the availability of more active sites, improved charge separation, rapid interfacial charge transfer process, higher injection ability, and higher water oxidation kinetics. The higher open circuit voltage (VOC) of BiVO4/Co3O4 offers the greater driving force for charge separation. On the other hand, the density functional theory (DFT) investigations were carried out for further understanding of the facile interfacial charge transfer process. The electrostatic plots from the DFT studies reveals that Co3O4 has a deeper potential than BiVO4 and this potential difference can induce a strong internal electric field across the junction which promotes facile charge transfer from BiVO4 to Co3O4 until equilibration. Under illumination, BiVO4 and Co3O4 act electron acceptor and hole acceptor, respectively. Hence, the hole accumulated water oxidation is taken place in the valence band maximum (VBM) of Co3O4 for an enhanced PEC performance of the p-n junction photoanode.