1. Could you explain the significance of your article to the non-specialist?

In this article we demonstrate that the proton conducting material, CsH₂PO₄, can be used in viable fuel cells. Fuel cells have received a great deal of attention as clean energy conversion devices, and this compound, a so-called solid acid, solves many of the challenges facing existing fuel cell technologies. There has been some debate as to whether or not this material truly exhibits high proton conductivity through its bulk, with some authors suggesting that the high conductivity is simply an artifact of the dehydration reaction. In this work, we put this debate to rest, showing without question that the high conductivity is due to bulk proton transport.

 

2. What has motivated you to conduct this work?

A combination of scientific curiosity and desire to develop technologies for a sustainable energy future. Several years ago, it appeared that the only solid acids that could support high proton transport were those based on sulfates or selenates. I wanted to know if there was something inherent in the chemistry of phosphorous (or arsenic) that would impede proton transport. The first experiments I did were on intermediate compounds involving both sulfate and phosphate groups. After finding that these compounds could indeed support high proton conductivity, I had my students look specifically at CsH₂PO₄, which, of course, has no sulfate groups. I was surprised and delighted to find that this material behaved very much like the related sulfates and selenates. I was even more delighted when we identified it to be the ideal fuel cell electrolyte because it, unlike the sulfates and selenates, is stable under both reducing and oxidizing atmospheres. 

 

3. Where do you see this work developing in the future?

From a fundamental scientific perspective, there are many questions regarding proton transport pathways and mechanisms through solid acid compounds like CsH₂PO₄. There are many groups around the world trying to address these questions, but much remains to be done. Ultimately, getting at the answers will be essential if we are to design materials with even more attractive properties, such as insolubility in water and higher mechanical strength.

 

4. Are there any particular challenges facing future research in this area?

It is hard to say that the challenges facing this research are unique relative to other areas of scientific inquiry. I might argue that there are unique challenges in terms of funding because this work falls in the grey area between basic and applied research, and therefore has not been enthusiastically embraced by any part of the US Department of Energy, which, in principle, should be supporting this work. There is also a challenge in terms of public perception and demand for alternative energy. The public wants clean and inexpensive options to be available now, but it will take years before the kinds of things that we do become commercially available. As we (collectively) work through the hard problems along the road of fuel cell technology demonstration, we risk the loss of public interest and support.