Visible-light responsive BiNbO₄ nanosheet photoanodes for stable and efficient solar-driven water oxidation

Area of Science:

• Materials Science
• Renewable Energy
• Electrochemistry

Background:

• Bismuth niobate (BiNbO4) is an emerging photoanode material for photoelectrochemical (PEC) solar energy conversion.
• BiNbO4 has a direct bandgap of ~2.6 eV and suitable band alignment for water oxidation/reduction.
• Efficient solar energy conversion requires optimized photoanode materials.

Purpose of the Study:

• To develop BiNbO4 nanosheets using a sol-gel and spin coating method.
• To investigate the effect of annealing temperature on BiNbO4 crystallinity and PEC properties.
• To compare the PEC performance of BiNbO4 with existing materials like BiVO4.

Main Methods:

• Sol-gel synthesis followed by spin coating to create BiNbO4 nanosheets.
• Optimizing annealing conditions, specifically comparing 500°C and 550°C.
• Photoelectrochemical measurements including photocurrent density and incident photon-to-current efficiency (IPCE).

Main Results:

• The BiNbO4 film annealed at 550°C showed improved crystallinity and enhanced PEC performance compared to the 500°C film.
• Photocurrent density reached 0.45 mA cm-2 at 1.23 V vs. the reversible hydrogen electrode (RHE) for the 550°C annealed film.
• The 550°C annealed BiNbO4 film exhibited 20% IPCE at 425 nm and stable photoresponse over 5 hours.

Conclusions:

• Optimized annealing temperature is crucial for enhancing BiNbO4 crystallinity and PEC properties.
• BiNbO4 annealed at 550°C demonstrates superior performance for photoelectrochemical water splitting.
• BiNbO4 presents a promising alternative to BiVO4 for sustainable solar energy conversion.