Solid-state photoelectrochemical cell with TiO₂ nanotubes for water splitting

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Traditional photoelectrochemical (PEC) cells utilize liquid electrolytes, posing challenges for device integration and long-term stability.
• Developing solid-state PEC devices is crucial for practical applications in solar energy conversion and water splitting.

Purpose of the Study:

• To fabricate and evaluate a novel solid-state PEC cell employing a proton-conducting Nafion® polymer membrane as the electrolyte.
• To investigate the influence of different titanium dioxide (TiO2) photoanode architectures, specifically thermally prepared films and ordered nanotubes (TNTs) of varying lengths, on cell performance.

Main Methods:

• Fabrication of a PEC cell with a TiO2-based photoanode and a Pt/C cathode, separated by a hydrated Nafion® membrane.
• Performance testing using photovoltammetry under asymmetric conditions (anode in water, cathode in air) with UV-A rich light illumination.
• Comparison of T-TiO2 films and TiO2 nanotubes (TNTs) of different lengths (1 μm and 8 μm) in deionized water and 0.5 M Na2SO4 electrolyte.

Main Results:

• High incident photon-to-current efficiency (IPCE) of 19% achieved with short TNTs (1 μm) under unassisted conditions (0 V) with UV-A light.
• Enhanced IPCE of 33% obtained with longer TNTs (8 μm) in 0.5 M Na2SO4, attributed to improved ionic conductivity within the nanotubes.
• Demonstration of a functional solid-state PEC cell with minimized electrode distance and device volume.

Conclusions:

• The solid-state PEC cell design utilizing a Nafion® membrane offers a promising alternative to traditional liquid electrolyte systems.
• Nanostructured TiO2 nanotubes, particularly longer ones, enhance performance due to increased ionic conductivity, paving the way for efficient solar water splitting.
• This approach facilitates the development of compact and practical PEC devices for solar energy conversion.