The Fast-Track Water Oxidation Channel on BiVO₄ Opened by Nitrogen Treatment

BiVO₄ is one of the most promising photoanode materials for water-splitting systems. Nitrogen incorporation into a BiVO₄ surface overcomes the known bottleneck in its charge-transfer kinetics into the electrolyte. We explored the role of nitrogen in the surface charge recombination and charge-transfer kinetics by employing transient photocurrent spectroscopy at the time scale of surface recombination and water oxidation kinetics, transient absorption spectroscopy, and X-ray photoelectron spectroscopy. We attributed the activity enhancement mechanism to the accelerated V⁵⁺/V⁴⁺ redox process, in which incorporated nitrogen suppresses a limiting surface recombination channel by increasing the oxygen vacancies.