Kenaf-derived carbon quantum dots-modified BiVO₄ thin film photoanodes for enhanced photoelectrochemical water...

Bismuth vanadate (BiVO₄) is a promising visible-light photocatalyst for PEC hydrogen production owing to its favourable band-edge positions, but its practical efficiency is hindered by rapid electron-hole recombination and consequently poor solar-energy conversion. Herein, a green approach using different loading amounts of kenaf-based carbon quantum dots (CQDs) as electron transfer mediators is applied to enhance the optical and electrical properties of the BiVO₄ photoanode. CQDs boosted the light absorption of the modified BiVO₄ photoanode across 300-800 nm and narrowed the band gap energy from 2.35 eV to 2.27 eV. In addition, the as-developed CQDs/BiVO₄ exhibited higher charge separation efficiency, with a 36.0% reduction in charge recombination at 469 nm. At 1.05 V vs. RHE, the optimum CQDs/BiVO₄ (CB-14) demonstrated a photocurrent density of 0.254 mA cm^-2, approximately two-fold higher compared to the unmodified BiVO₄. It also exhibited a 166.7% increment in photoconversion efficiency upon modification with kenaf-based CQDs (CB-14). An average hydrogen evolution of 10.83 µmol cm^-2 h^-1 was recorded by CB-14, which is 1.67 times higher compared to the unmodified BiVO₄.