Enhancing photoelectrochemical surface reactivity through interface grafting of g-C3N4 quantum dots with BiVO4

Abstract

Due to the high photosensitivity, quantum dots (QDs) offer promise in establishing heterojunctions to improve the photoelectrochemical (PEC) water oxidation process and enhance the solar-to-hydrogen conversion efficiency. However, apart from their catalytic capacity, additional protection strategies should be considered to eliminate the destruction of QDs from electrolytes and photo-corrosion. Here, we present a facile strategy to fabricate heterojunction by employing graphitic carbon nitride QDs (g-C3N4 QDs) coupled with BiVO4, referred to CNQDs/BiVO4. With the help of CNQDs, a gradient energy band alignment has been established in CNQDs/BiVO4, leading to facilitated hole migration driven by an upward force. The optimal CNQDs/BiVO4 sample shows significantly enhanced PEC performance for water oxidation, with a photocurrent of 2.2 mA/cm2 at 1.23 V vs. RHE (reversible hydrogen electrode), which is about 2.26 times better than that of BiVO4 (0.97 mA/cm2). The enhanced PEC performance could be attributed to the increased surface-active area and facilitated surface oxidation kinetics.