Integration of surficial oxygen vacancies and interfacial two-dimensional NiFe-layered double hydroxide nanosheets onto bismuth vanadate photoanode for boosted photoelectrochemical water splitting

Considering its outstanding cost-to-efficiency ratio, N-type bismuth vanadate (BiVO4) is an ideal photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the widespread application of BiVO4 is being hindered commercially by innate challenges such as its poor carrier mobility, short hole diffusion length, and sluggish oxidation chemistry. Herein, we report the unique integration of surficial oxygen vacancies (O-vac) in conjunction with two-dimensional (2D) nickel-iron (NiFe) layered double hydroxide (LDH) nanosheets onto pristine BiVO4 photoanode to tweak the charge transfer kinetics during water splitting. The introduction of oxygen vacancies efficiently modulates band energetics, amplifies light absorption, and augments the carrier density. Concurrently, the 2D NiFe-LDH nanosheets play a dual role by facilitating interfacial hole transfer, thereby reducing excessive defect states, and serving as a protective layer against photocorrosion, ultimately resulting in a notable improvement in solar-driven water oxidation efficiency. The results of PEC water-splitting experiments demonstrate that the BiVO4 photoanode enriched with surficial oxygen vacancies and NiFe-LDH (BiVO4:O-vac/NiFe-LDH) achieved a photocurrent density of 2.92 mA cm(-2) with similar to 3-fold enhancement compared with a pristine BiVO4 photoanode. The engineered BiVO4 system yielded an impressive photoconversion efficiency of 1.29 %, charge separation efficiency (eta(sep)) > 40 %, and charge transport efficiency (eta(trans)) > 35 %, clearly evidencing a boost in the charge dynamics of pristine BiVO4. Furthermore, during long-term stability testing, BiVO4:O-vac/NiFe-LDH retained 91 % of its initial photocurrent density for similar to 20 h without any significant deterioration. This work sheds light on the role of integrating surface and interface engineering tactics for enhancing photo-induced charge transport in BiVO4, thereby providing efficient and stable PEC water splitting.

Automated summary

This study reports the integration of surficial oxygen vacancies and 2D NiFe-LDH nanosheets to enhance the charge transfer kinetics of BiVO4 photoanode for PEC water splitting. The introduction of oxygen vacancies modulates band energetics, enhances light absorption and carrier density, while the 2D NiFe-LDH nanosheets facilitate interfacial hole transfer and serve as a protective layer against photocorrosion. The engineered BiVO4 system achieved a significant improvement in photocurrent density and solar-driven water oxidation efficiency.