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Enhancing Proton Mobility in Silicophosphoric Acid by Replacing Si with Al
Tomohiro Ishiyama1, Yuya Yamada2, Hiroki Nagashima3
1Research Institute for Energy Conservation, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
Replacing silicon with aluminum in phosphate glass proton conductors significantly boosts conductivity for high-temperature fuel cells. This advancement supports the development of next-generation energy conversion devices crucial for carbon neutrality.
Area of Science:
- Materials Science
- Electrochemistry
- Solid-state Chemistry
Background:
- High-temperature electrochemical devices (200-300 °C) are vital for next-generation fuel cells and electrosynthesis, contributing to carbon neutrality goals.
- Phosphate glasses are promising proton conductors for these demanding applications.
- Previous research developed silicophosphoric acid glass proton conductors, but suffered from low conductivity due to proton trapping by silicon.
Purpose of the Study:
- To enhance proton conductivity in phosphate glass proton conductors.
- To investigate the effect of substituting silicon with aluminum on proton conductivity and thermal stability.
- To understand the underlying mechanisms for conductivity improvement.
Main Methods:
- Synthesis of aluminum-containing phosphate glass proton conductors.
- Measurement of proton conductivity at elevated temperatures.
- Characterization of glass structure and properties using Nuclear Magnetic Resonance (NMR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).
Main Results:
- Proton conductivity improved by one order of magnitude upon replacing silicon with aluminum.
- Thermal stability of the glass proton conductor was maintained.
- Spectroscopic analyses confirmed no significant structural changes in the glass framework after substitution.
Conclusions:
- Aluminum substitution effectively mitigates proton trapping compared to silicon in phosphate glasses.
- The improved proton conductivity is attributed to the distinct electrical properties of aluminum versus silicon, weakening proton-trapping effects.
- This work presents a viable strategy for developing advanced proton conductors for high-temperature electrochemical applications.
