Naing, Myat ThweHwang, Jun BeomLee, JeongsuKim, YejoonJung, YoonsungLee, Sanghan2026-03-282026-03-280360-3199https://hdl.handle.net/1885/733807976The performance of photoelectrochemical (PEC) water splitting is hindered by high overpotential and significant recombination of photogenerated charges occurring within the bulk and on the surface of the photoanodes. In this study, we propose a nanoporous photoelectrode, B–Co:BVO, which combines ex-situ Co-doping and surface borate impregnation treatments through simple electrodeposition and immersion methods. As a result, the optimized photocurrent densities of B-BVO and Co:BVO exhibit 1.58 mA/cm2 and 1.9 mA/cm2, respectively, showing a 1.3 and 1.6-fold increase compared to the bare BVO sample (1.2 mA/cm2) at 1.23 VRHE. Moreover, the synergistic effect of Co doping and borate impregnation on the BiVO4 photoanode (B–Co:BVO) achieves the photocurrent density of 2.27 mA/cm2, accompanied by a lower onset potential (0.23 VRHE) and highest IPCE value (42.6 %) at 1.23 VRHE, maintaining 80.4 % of initial current density value for 18 h in KBi + V electrolyte solution with the enhancement of PEC performance. The proposed charge transfer mechanism in optimum B–Co:BVO photoanodes during the photoelectrochemical water splitting was also studied.This work was supported by the program of Future Hydrogen Original Technology Development (No. 2021M3I3A1084747 ), through the National Research Foundation of Korea (NRF) , funded by the Korean government (Ministry of Science and ICT(MSIT) ); by the NRF grant funded by the Korea government ( MSIT ) (No. 2020R1A2C1005590 ); and the GIST-MIT Research Collaboration grant funded by the GIST.9en©2023 The authorsBiVOBorate impregnationCo-dopingPhotoelectrochemical (PEC) water splittingSynergistic effect2023-11-2210.1016/j.ijhydene.2023.11.15585179666063