Fabrication of Cocatalyst NiO-Modified BiVO₄ Composites for Enhanced Photoelectrochemical Performances

In this work, NiO modified BiVO₄ (BiVO₄/NiO) nanocomposite was synthesized using hydrothermal and calcination method. The composite of BiVO₄/NiO, further employed as a low-overpotential photoanode, was consisted of BiVO₄ nanoparticles and NiO nanosheets, in which the BiVO₄ nanoelectrode served as the matrix for the attachment of NiO nanosheets. Photoelectrochemical (PEC) tests show that BiVO₄/NiO displayed improved PEC performance compared with pure BiVO₄. The BiVO₄/NiO photoanode delivers a photocurrent density of 1.2 mA/cm² at 1.23 V vs. RHE in a Na₂SO₄ electrolyte under an AM 1.5G solar simulator, which is 0.3 mA/cm² higher than pure BiVO₄ photoanode. Meanwhile, the onset potential also generates a 350 mV cathodic shift. The enhanced performance of the BiVO₄/NiO nanocomposite is attributed to NiO unique lamellar structure capable of providing a large number of active sites. Measurements of electrochemical impedance spectra (EIS) and the incident photon-to-current efficiency (IPCE) illustrate that the enhanced PEC activities are ascribed to the improved charge carrier separation/transport and the promoted water oxidation kinetics furnished by the decoration of NiO cocatalyst.