Visible-light responsive BiNbO 4 nanosheet photoanodes for stable and efficient solar-driven water oxidation.

Herein, we report bismuth niobate (BiNbO4), which is regarded as an emerging photoanode material for sustainable photoelectrochemical (PEC) solar energy conversion. BiNbO(4)possesses a direct bandgap (E-g) of similar to 2.6 eV, and shows an appropriate band alignment for the water oxidation/reduction reaction. In this study, a simple sol-gel route followed by a spin coating method was applied to develop BiNbO(4)nanosheets under the optimum annealing conditions. It is known that the annealing temperatures of 500 and 550 degrees C influence the crystallinity and PEC properties of BiNbO(4)films. In particular, the 550 degrees C annealed film exhibited sharply improved crystalline properties, and rapidly enhanced PEC performance, which were accompanied by a photocurrent density of 0.45 mA cm(-2)at 1.23 Vvs.the reversible hydrogen electrode (RHE) (briefly abbreviated as 1.23V(RHE)) in a strong alkaline solution of 1 M NaOH, compared with 0.26 mA cm(-2)at 1.23V(RHE)of the 500 degrees C annealed film. This may be attributed to the main increase of the crystallinity, as well as the improvement of the electronic properties. In addition, the BiNbO4(550 degrees C) film showed an incident photon-to-current efficiency of 20% at 425 nm, and produced a stable photoresponse under light illumination in a strong alkaline solution over 5 h, compared with a BiVO(4)electrode.