Pure Water-Fed Photoelectrochemical Water Splitting Using a Porous WO₃ Electrode Surface-Modified With...

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Photoelectrochemical (PEC) water splitting offers a sustainable route for hydrogen fuel production.
• Proton exchange membrane (PEM)-PEC systems are crucial for efficient renewable energy storage.
• Operating PEC systems in pure water without supporting electrolytes presents significant challenges in proton transport.

Purpose of the Study:

• To investigate the performance of a PEM-PEC system using pure water without supporting electrolyte.
• To enhance hydrogen production efficiency by surface-modifying a porous tungsten oxide (WO3) photoanode with a perfluorosulfonic acid (PFSA) ionomer.
• To analyze the impact of ionomer loading on proton transport and overall water splitting efficiency.

Main Methods:

• Fabrication of a porous WO3 photoanode.
• Surface modification of the WO3 photoanode with a PFSA ionomer coating.
• PEC water splitting experiments under UV irradiation (365 nm) with an applied cell voltage (1.2 V).
• Incident photon-to-current conversion efficiency (IPCE) measurements.
• Product analysis (oxygen and hydrogen evolution).

Main Results:

• The PFSA ionomer-modified WO3 electrode achieved an IPCE of 36%, a significant improvement from the unmodified electrode's 15%.
• The pure water-fed system demonstrated an IPCE of 35%, comparable to vapor-fed systems, with minimal ionomer loading (0.06 mg cm⁻²).
• Product analysis confirmed efficient water splitting with oxygen evolution at the photoanode and hydrogen at the cathode.
• Photocurrent density showed a direct correlation with light intensity and followed the bandgap absorption of WO3.

Conclusions:

• PFSA ionomer loading effectively overcomes proton transport limitations in electrolyte-free PEM-PEC water splitting systems.
• Surface protonics of porous photoanodes play a critical role in enhancing the efficiency of PEM-PEC devices.
• This approach demonstrates a promising pathway for efficient and cost-effective hydrogen production using pure water.