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.