Photoelectrochemical (PEC) water splitting is a promising method for storing solar energy in the form of hydrogen fuel, but it is greatly hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Herein, a facile solution impregnation method is developed for growing ultrathin (2 nm) highly crystalline β-FeOOH nanolayers with abundant oxygen vacancies on BiVO photoanodes. These exhibited a remarkable photocurrent density of 4.3 mA cm at 1.23 V (vs. reversible hydrogen electrode (RHE), AM 1.5 G), which is approximately two times higher than that of amorphous FeOOH fabricated by electrodeposition. Systematic studies reveal that the excellent PEC activity should be attributed to their ultrathin crystalline structure and abundant oxygen vacancies, which could effectively facilitate the hole transport/trapping and provide more active sites for water oxidation.

Effective HER activity on layered double hydroxide nanosheets through a plasma etching strategy.

Improving charge transport and reducing bulk/ surface recombination can increase the activity and stability of BiVO 4 for water oxidation. Herein we demonstrate that the photoelectrochemical (PEC) performance of BiVO 4 can be significantly improved by potentiostatic photopolarization. The resulting cocatalyst-free BiVO 4 photoanode exhibited a record-high photocurrent of 4.60 mA cm À2 at 1.23 V RHE with an outstanding onset potential of 0.23 V RHE in borate buffer without a sacrificial agent under AM 1.5G illumination. The most striking characteristic was a strong "self-healing" property of the photoanode, with photostability observed over 100 h under intermittent testing. The synergistic effects of the generated oxygen vacancies and the passivated surface states at the semiconductor-electrolyte interface as a result of potentiostatic photopolarization reduced the substantial carrier recombination and enhanced the water oxidation kinetics, further inhibiting photocorrosion.