Nanotip effect assisted in situ growth of ZIF-67 nanoflowers on a BiVO4 photoelectrode to boost photoelectrochemical water oxidation

Abstract

The sluggish kinetics of BiVO₄ limits its applications in solar-to-hydrogen energy conversion. In this work, the zeolitic imidazolate framework ZIF-67 as a cocatalyst was immobilized on a BiVO₄ nanocone via a solution-based photo-deposition method for photoelectrochemical water oxidation. Under the assistance of the nano-tip effect induced by the BiVO₄ tip, nanoflower-like ZIF-67 was selectively grown at the vertex of the BiVO₄ nanocone. The constructed BiVO₄/ZIF-67 composite photoelectrode yielded a photocurrent of 0.92 mA cm⁻² at ∼1.23 V_RHE, which is about 3.5-fold that of pure BiVO₄. In addition, surface/bulk charge separation efficiencies (η_surf and η_bulk) were elevated when compared to those of the BiVO₄ photoelectrode. Photoelectrochemical impedance spectroscopy (PEIS) and intensity modulated photocurrent spectroscopy (IMPS) measurements were further investigated to reveal the critical role of the modification of ZIF-67 in suppressing charge recombination and improving the photoelectrochemical activity of BiVO₄. This research presents a feasible way to design a BiVO₄/MOF composite photoanode induced by the nano-tip effect for enhanced photoelectrochemical water splitting performance.