Oxygen‐Rich Carbon Nitride Quantum Dots Engineered Bismuth Vanadate Photoanode Surface to Achieve Highly Efficient Solar Water Oxidation

This study proposes a strategy for passivating intrinsic oxygen vacancies (Ovac) on BiVO 4 photoanodes through surface modification with carbon nitride quantum dots (CNQDs). The BiVO 4 ‐CNQDs photoanode was fabricated via chemical bath deposition and calcination, achieving significant Ovac suppression without compromising the crystallinity of the BiVO 4 framework. This Ovac reduction critically alters the thermodynamic landscape of water oxidation by modulating intermediate adsorption energetics, steering the reaction pathway toward selective H 2 O 2 generation. The optimized BiVO 4 ‐CNQDs photoanode demonstrates a 24.91% average Faradaic efficiency (FE) for H 2 O 2 production, representing a 1.38‐fold enhancement over the pristine BiVO 4 photoanode. By integrating an In 2 O 3 passivation layer, a BiVO 4 ‐CNQDs‐In 2 O 3 photoanode was formed, and the average FE of H 2 O 2 preparation reached 28.16%, achieving further performance improvement. The generated electrons and holes can be more effectively transferred from BiVO 4 to the In 2 O 3 passivation layer before participating in subsequent electrochemical reactions. This dual modification synergistically promotes the quasi‐Fermi level of holes to move toward the anode and reduces band bending, synergistically driving photo generated holes toward the higher oxidation potentials to accelerate the selective conversion of H 2 O to H 2 O 2 . The BiVO 4 ‐CNQDs‐In 2 O 3 photoanode achieves a 1.58‐fold improvement in average H 2 O 2 FE within the 1.2–2.4 V versus reversible hydrogen electrode (RHE) range compared to unmodified BiVO 4 . This work establishes an innovative approach for modulating inherent Ovac in BiVO 4 photoanode and optimizing the preparation pathway of H 2 O 2 through the vacancy engineering.