Vastly Enhanced BiVO₄ Photocatalytic OER Performance by NiCoO₂ as Cocatalyst

Here, a simple and efficient preparation of NiCoO₂ nanoparticle modified nanoporous bismuth vanadate (BiVO₄) thin film and its application in photoelectrocatalytic (PEC) oxygen evolution reaction (OER) is demonstrated. The role of NiCoO₂ in the composite electrode (BiVO₄/NiCoO₂) is twofold: OER cocatalyst and band structure modifier. It improves surface reaction kinetics for PEC OER and enhances charge separation efficiency simultaneously, which is believed to be a determining factor for the unprecedentedly high PEC OER performance of this BiVO₄/NiCoO₂ nanocomposite. The photocurrent density of 3.6 mA cm⁻² at 1.23 V versus RHE in 0.1 m potassium phosphate buffered (pH = 7) electrolyte by BiVO₄/NiCoO₂ is three times that of BiVO₄ and significantly higher than most literature values. The BiVO₄/NiCoO₂ nanocomposite shows/possess a high charge separation efficiency (η_surface) of ≈72% as compared to only 23% for pure nanoporous BiVO₄ at 1.23 V versus RHE, which demonstrates convincing role of NiCoO₂ in the composite electrode. Both the excellent photocurrent density and great operational stability of this BiVO₄/NiCoO₂ nanocomposite makes it a promising photocatalytic material for practical applications.