Transparent WO3 film breakthrough boosts hydrogen production efficiency

Transparent WO3 film breakthrough boosts hydrogen production efficiency
by Riko Seibo
Tokyo, Japan (SPX) Sep 07, 2025

A research team at Niigata University has developed a transparent crystalline mesoporous tungsten trioxide (WO3) film that significantly enhances efficiency and durability in photoelectrochemical (PEC) water splitting. The innovation marks a step forward in solar-to-hydrogen conversion, offering a scalable route to sustainable fuel generation.

The team engineered the WO3 film directly onto a conductive fluorine-doped tin oxide (FTO) substrate using a surfactant-template process with in situ template-carbonization. This method, employing the triblock copolymer Pluronic F127, produced a crystalline mesoporous network with ultrathin 10 nm pore walls and a surface area of 124 m/g. The resulting structure improves charge transport, provides abundant reaction sites, and maintains transparency for tandem PEC devices.

Lead author Dr Debraj Chandra noted that "in situ template-carbonization technique preserves the uniquely crystalline organized-mesoporous structure of WO3 film. The materials fabrication technique is promising for development of other unattained crystalline mesoporous metal oxide films."

Performance testing showed the mesoporous WO3 photoanode reached photon-to-current conversion efficiencies of 49% in acidic and 41% in neutral pH at 420 nm and 1.23 V versus the reversible hydrogen electrode. Compared to standard WO3 films, the water oxidation rate constant increased 3.6-fold. Incorporating cobalt oxide nanoparticles further accelerated surface reactions, raising the oxygen evolution rate constant to 5.7 + 10 s-1, with faradaic efficiency reaching 93%.

Durability trials revealed the mesoporous WO3 electrode retained 98% of its photocurrent after 30 hours of continuous neutral-condition operation. The optical transparency allows it to serve as a front light-harvesting layer in tandem PEC devices, improving efficiency by capturing a wider solar spectrum.

Corresponding author Dr Masayuki Yagi emphasized, "The high optical transparency and exceptional long-term stability under neutral pH conditions of the mesoporous WO3 electrode provides a scalable strategy for tandem photoelectrochemical water splitting devices by using it as a front light-harvested layer, thereby advancing the prospects of sustainable solar-driven water splitting".

The study highlights a pathway toward robust and efficient photoanodes for hydrogen production, addressing stability and performance limitations of current materials. The scalable fabrication strategy may also apply to other oxide semiconductors, potentially broadening its impact on renewable hydrogen technologies.

Research Report:Optically transparent WO3 films with organized mesopores and oriented crystallinity: An efficient and robust photoanode for visible-light-driven water oxidation at neutral pH