Self-Diffusion versus Intentional Doping: Beneficial and Damaging Impact on Hematite Photoanode Interfaces

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Efficient solar water splitting devices require optimized (photo)electrode design.
• High-temperature thermal treatments are crucial but can introduce unintended side effects.
• Understanding ion diffusion during thermal processing is key to controlling (photo)electrode properties.

Purpose of the Study:

• To investigate the impact of thermal treatments on (photo)electrode design for solar water splitting.
• To analyze the beneficial and detrimental effects of ion self-diffusion in hematite photoabsorbers.
• To evaluate the role of substrate properties and ion migration on photoelectrochemical performance.

Main Methods:

• Fabrication of hematite photoabsorbers using the polymeric precursor synthesis (PPS) method.
• Thermal treatment of conductive glass substrates (ABS/FTO and QTZ/FTO).
• Analysis using optical, structural, and X-ray photoelectron spectroscopy (XPS).

Main Results:

• Thermal treatments did not significantly alter substrate optical or structural properties.
• XPS revealed migration of Si⁴⁺ and Ca²⁺ from glass, and Sn⁴⁺ from FTO to the hematite surface.
• Detected ion self-diffusion did not enhance hematite photoelectrochemical response; intentional modifications were more impactful.

Conclusions:

• Unintentional ion self-diffusion during thermal treatment of hematite photoelectrodes does not significantly improve photocurrent.
• Intentional doping or surface modification strategies are more effective for enhancing photoelectrochemical efficiency.
• Controlling thermal treatment effects is crucial for developing efficient and cost-effective solar water splitting devices.