Carbon quantum dots (CQDs) modified α-Fe2O3/BiVO4 heterojunction photoanode for enhancing photoelectrochemical water splitting

•The Fe2O3/BiVO4 heterojunction has been successfully synthesised. This heterostructure enables effective separation of electron-hole pairs and reduces the complex probability of photogenerated carriers.•Modification of CQDs can improve the OER kinetics and enhance the interfacial charge transfer kinetics of the photoanode.•The CQDs modified α-Fe2O3/BiVO4 ternary photoanode exhibits excellent photoelectrochemical performance, it can be a thoroughly viable and economical potential candidate material for improving the performance of photoelectrochemical water splitting. The design of photoanode materials to achieve efficient water splitting is a current research hotspot in photoelectrochemical (PEC). In this work, we designed and prepared an α-Fe2O3/BiVO4 heterostructure modified by carbon quantum dots ((α-Fe2O3/BiVO4/CQDs)) as the photoanode. The modification of CQDs can broaden the sunlight absorption ability and dramatically enhance the water oxidation kinetics of α-Fe2O3/BiVO4/CQDs. The optimized photoanode demonstrated a photocurrent density of 1.32 mA·cm−2 at 1.23 V vs. RHE, which is 2.2 times than pristine α-Fe2O3 (0.6 mA·cm−2) photoanode. The IPCE value above 29.4 % at 400 nm, and the onset potential is negatively shifted by 243 mV for α-Fe2O3/BiVO4/CQDs. The improved performance is mainly due to the α-Fe2O3/BiVO4 heterojunction to achieve effective separation of photogenerated carriers in the bulk phase and CQDs to improve light utilisation and OER kinetics of the photoanode. [Display omitted] The ternary photoanode of CQDs modified Fe2O3/BiVO4 was successfully fabricated, which achieve efficient PEC water splitting performance.