Enhanced charge separation through oxygen vacancy-mediated anchoring of CoNi-ZIF on BiVO4 photoanodes

Surface OVs act as robust atomic anchors to capture CoNi-ZIF on BiVO 4 . • Defect anchoring drives ∼4.0 e⁻ transfer for efficient charge separation. • Built-in electric field significantly lowers the OER activation energy barrier. • The engineered interface yields 4.16 mA cm⁻ 2 with an exceptional 97.6% stability. • This heterojunction achieves dual PEC water splitting and MB degradation. Bismuth vanadate (BiVO 4 ) is extensively investigated for solar-driven photoelectrochemical (PEC) applications. However, its performance is largely limited by severe bulk charge recombination and sluggish surface reaction kinetics. In this work, a strategy combining defect engineering with in-situ self-assembly was developed to construct a planar photoanode, which integrates an oxygen-vacancy-rich BiVO 4 (OV-BVO) skeleton with a strongly coupled bimetallic CoNi-zeolitic imidazolate framework (CoNi-ZIF) cocatalyst layer. Experimental characterizations combined with density functional theory (DFT) calculations reveal that the introduced oxygen vacancies (OVs) play dual critical roles. In the bulk, OVs induce V 4 ⁺ polaron states, significantly enhancing intrinsic conductivity and visible-light absorption. At the interface, OVs serve as atomic anchoring sites, inducing a substantial electron transfer of ∼4.0 e and generating a strong built-in electric field (maximum photovoltage of 418.1 mV). This efficiently drives photogenerated holes into the CoNi-ZIF layer, achieving a surface hole injection efficiency exceeding 80%. Consequently, the optimized OV-BVO/CoNi-ZIF photoanode delivers a photocurrent density of 4.16 mA cm⁻ 2 at 1.23 V vs. RHE (2.6 times that of Pure BVO) and maintains stable continuous operation without structural degradation. This study elucidates the defect-mediated charge transfer mechanism at the atomic scale, providing specific design strategies for advanced photoanodes in solar energy conversion. Download: Download high-res image (161KB) Download: Download full-size image