Olivier Joubert, a researcher who is boosted by hydrogen

Even when he is jogging on the bank of the river Erdre, the Nantes researcher Olivier Joubert never lets his mind wander from his research subject: hydrogen. Whilst running during his lunch break, he finds it hard to avoid glancing at the Navibus-H2, the fluvial shuttle powered by hydrogen fuel cells. Olivier Joubert is obsessed by the use of hydrogen as an energy source. It is impossible for him to take a break from this as he is the CNRS representative for Afhypac, an association promoting hydrogen fuel cells, the director of a research group bringing together 77 laboratories working on hydrogen (HySPàC) as well as the director of the "Matériaux pour pile à combustible et électrolyseur" (Materials for fuel cells and electrolyzers) research team at the Jean Rouxel Institute of Materials (CNRS/University of Nantes). Given the circumstances, it is difficult for him to let his mind wander far from science. "I do manage it" claims the marathon runner of science as he takes a breather. "Mostly by cooking or DIY" he says.

Olivier Joubert works on a quest to find new materials for fuel cells and electrolyzers. "Ideally dihydrogen is produced by an electrolyzer that electrically transforms water into its two components thanks to electricity," explains the researcher briefly. "Dihydrogen can then be stored, transported and used in a fuel cell to produce electricity. The reaction only gives off water and a little heat." In this cycle, hydrogen becomes an "energy vector" just like electricity. At each end of this chain, chemical reactions occur on the electrodes and electrolyte of the battery or electrolyzer. This is the core subject of Olivier Joubert's research. "We need to understand that these chemical reactions produce or use electricity and electrically charged particles. Electricity flows outside the battery from one electrode to another and can be used to power an electrical device. The charged particles or ions circulate inside the cell through the electrolyte. The problem is the slowness of both the chemical reactions on the electrodes and the flow of ions through the electrolyte. My contribution to science, if I can put it that way, is to find electrode materials and electrolyte materials that are effective ionic conductors. More specifically, I'm looking for ceramic materials with these properties."

Exploratory research

An electrolyzer actually looks like the images of the first Volta column batteries invented in 1800. Instead of an assembly, Olivier Joubert uses alternating ceramic plates (electrode-electrolyte-electrode) which he makes himself. The challenge is to discover materials capable of transporting ions efficiently at feasible temperatures. "To give just one example, EDF and I patented an oxide composed of barium, indium and titanium. It is an excellent material with an ionic conductivity 100 times higher than that of conventional material at the same temperature." This material could even have been used in solid oxide fuel cells (SOFCs) but it remains difficult for it to find a place in industry. "It is difficult to deal with technology transfer," explains Olivier Joubert laconically. "Changing materials in an industrial process almost requires the entire industrial chain to be rethought."

This exploratory research involves a great deal of uncertainty and can also bring up unexpected opportunities. "Last year, we published an article on a ceramic material made of potassium borate. It has an amazing level of conductivity which we didn't expect. Instead of conducting oxygen ions, it conducts potassium ions. It was interesting but we stopped at that point because its conductivity was low. But now research teams are taking a close interest in solid batteries and this material is being reused in research that we had not imagined at the time which opens up a lot of perspectives." This proves that a contribution to the great book of science may not seem essential at the time of writing but will always end up being useful for someone somewhere.