In 2018, a full third of the world’s electricity production was based on renewable energies. In this context of rapid growth, hydrogen is emerging as a powerful storage solution to remedy the intermittent nature of solar and wind power. Hydrogen can be produced using an electrolyser, which, when coupled with a fuel cell, makes it possible to reconvert the stored energy into electricity for a wide range of applications. However, fuel cell and electrolyser performance tends to diminish over time. In order to optimize their performance, French researcher Olivier Joubert and his team at the Jean Rouxel Institute of Materials, a joint unit of the CNRS and the University of Nantes, are studying the properties of new materials. Their goal is to increase the life span and efficiency of these energy converters, in order to promote the future widescale deployment of hydrogen solutions.
"The coming bans on internal combustion vehicles in several cities will accelerate the roll-out of electric mobility and the hydrogen solution along with it."
For three or four years, I have seen a lot of momentum around hydrogen, notably from industry. I think changes in regulations partly account for this fact. The coming bans on internal combustion vehicles in several cities will accelerate the roll-out of electric mobility and the hydrogen solution along with it. Hydrogen is more advantageous than battery systems for a number of reasons: refueling time, range, etc. In the mobility sector, France has gained steam by investing in captive fleets like taxis, buses and service vehicles. This is a good strategy for implementing hydrogen solutions, while waiting for the cost of personal vehicles to become more accessible and for the number of fueling stations to grow across the country. Supply is another issue to consider: it involves not only producing hydrogen from renewable energies, but also the delivery infrastructure in place, both of which must expand further.
Olivier Joubert, French researcher at the Jean Rouxel Institute of Materials, a joint unit of the CNRS and the University of Nantes.
I work on systems called fuel cells, which convert the chemical energy of hydrogen directly into electricity, as well as the reverse systems which are electrolysers. Fuel cells and electrolysers can be split into two types based on their operating temperature: low-temperature systems, composed of polymer membranes, and high-temperature based on ceramic membranes. The first are known as “PEM” (Proton Exchange Membrane) and the second are “SO” (Solid Oxide). The ceramic membranes used in solid oxide systems are derived from zirconium oxide, a compound better known as yttria-stabilized zirconia. While this material offers several advantages such as cost, it tends to react with other compounds as the system’s temperature rises, which reduces its efficiency. My research consists therefore in finding new ceramic materials with physical properties that are as good if not better than yttrium-stabilized zirconia, in order to boost the performance of high-temperature energy converters. Together with the French electricity producer and distributor EDF, I notably patented an oxide composed of barium, indium and titanium. It’s an excellent material with an ionic conductivity that is one hundred times greater than the usual material at the same temperature.
"High-temperature electrolysers currently exist only in the demonstration phase [...]. When their use becomes more widespread, they will make it possible to produce decarbonized hydrogen at a cost that is comparable to the hydrogen currently produced from hydrocarbons."
Low-temperature fuel cells are used mainly in mobile applications like transport, because they are operational immediately. Their operation does not require any significant heating, unlike high-temperature fuel cells. The latter are most often suited to more stationary uses: for example, supplying a continuous current to power data centers or buildings. This is already the case in Japan, where many households are equipped with hydrogen power boilers that generate electricity. On the other hand, high-temperature electrolysers currently exist only in the demonstration phase with a single vendor on the market, based in Germany. When their use becomes more widespread, they will make it possible to produce decarbonized hydrogen at a cost that is comparable to the hydrogen currently produced from hydrocarbons. Some companies are taking a close interest in this technology, such as Sylfen which developed a reversible high-temperature system with the CEA (French Alternative Energies and Atomic Energy Commission). By coupling hydrogen with traditional batteries, this technology will help to store locally produced renewable energy and redistribute it as necessary.
Fuell cell test.
High-temperature systems offer greater electrical efficiency. Their efficiency is on the order of 60-70% for high-temperature fuel cells, compared to 40-50% for low-temperature fuel cells. In mobile applications, this difference stems from the need to incorporate a cooling system to limit the temperature rise, which reduces efficiency as a result. However, this is not the case for high-temperature fuel cells, where the heat released maintains high efficiency. That being said, it is important to keep in mind that the efficiency of fuel cells and electrolysers is necessarily constrained by the amount of electricity originally generated. Beyond efficiency, the real question we should ask is about the life cycle of energy converters: how long can they be used? And how can we ensure that the performance of these systems varies as little as possible over time?
The cost of low-temperature fuel cells derives mainly from platinum, used as a catalyst, and the Nafion membrane developed by the American company Du Pont de Nemours. Current research is working to lower the platinum content to around 10g – compared with 30g today in a 100 kW fuel cell – and to substitute a more economical membrane that can operate at a higher temperature. Things are a little different for high-temperature fuel cells because the cost does not depend solely on the materials. It also depends on how the materials are shaped at high temperatures, in order to obtain the ceramic after several cycles in the furnace. The key challenge now is to find cheaper materials and shaping processes.
Not all the elements of the periodic table that are known as rare earths are in fact geologically rare, like cerium, but some have a strong economic and strategic interest. With my team at the Jean Rouxel Institute of Materials, we focus on elements of the periodic table that are abundant on the planet at a relatively low cost. This also makes it possible to maintain a measure of independence from countries that could take advantage of a monopoly. Russia, for example, is one of the main suppliers of scandium, a rare earth that has more valuable properties than the yttrium used in the ceramic membrane. But we avoid using it so as not to be constrained by the market.
"Numerous studies are now looking at ways to recycle the materials used in low-temperature fuel cells, especially the costly platinum, 95% of which can now be recovered."
Numerous studies are now looking at ways to recycle the materials used in low-temperature fuel cells, especially the costly platinum, 95% of which can now be recovered. On the other hand, few research teams are studying this issue for high-temperature fuel cells. The resources available on the market are adequate for the moment, but in a context of geological scarcity or economic constraints, they could certainly become a strategic issue as well. There is already a lot of talk about this with lithium, for which there are a limited number of suppliers worldwide. In the laboratory, we are fortunate to have a doctoral student working on recycling the ceramic materials from fuel cells and electrolysers. That allows us to get a head start on the processes for recomposing these systems from recycled materials, and therefore at lower costs.
"High-temperature fuel cells [...] have benefited from major technological leaps forward. These advances, both in terms of materials and fuel cell architecture, have made it possible to design more innovative, sustainable and competitive systems."
The development of new catalysts and the steady decline in platinum content are among the improvements made to low-temperature fuel cells. But the main advances are found in high-temperature fuel cells. Although less mature, these have benefited from major technological leaps forward with the discovery of alternative electrode materials, as well as the development of a multilayer shaping process to improve their stability and performance. These advances, both in terms of materials and fuel cell architecture, have made it possible to design more innovative, sustainable and competitive systems compared to systems based on polymer membranes.
In France, funding for hydrogen research projects has tended to pick up again after a slowdown. This is due in part to the structuring of the CNRS (French National Centre for Scientific Research), which facilitates exchanges and collaborations between players in the same field. For example, I head a CNRS research federation (FRH2) dedicated to hydrogen, systems and fuel cells, which brings together 150 people at 28 laboratories. This momentum around hydrogen can also be observed internationally in countries such as Japan, the United States and Germany. However, it is above all applied research that is encouraged in a context of industrial deployment. Upstream research, the research that prepares the next generations of fuel cells and electrolysers, is still suffering from a lack of targeted funding.
"Industry is looking to institutions for a helping hand to facilitate the deployment of its activities across the entire chain. It also relies on R&D to improve existing systems, solve specific problems and stay one step ahead of the market."
Yes, of course. I am pleased to sit on the Board of Directors of the French Association for Hydrogen and Fuel Cells (Afhypac) as a representative of the CNRS. This association mainly brings together industrialists and institutional players, but also researchers with the ambition of accelerating the development of the hydrogen industry in France. Afhypac thus enables the various stakeholders to meet and discuss their respective needs. Industry is looking to institutions for a helping hand to facilitate the deployment of its activities across the entire chain. It also relies on to improve existing systems, solve specific problems and stay one step ahead of the market. In my field, that means identifying the high-performance materials that will be used to manufacture the electrolysers and high-temperature fuel cells that will be sold in ten or twenty years!
"The systems are viable and it is safe to drive a hydrogen-powered car."
Safety is a non-issue that was solved a long time ago. Like any fuel, this gas requires certain precautions for its use which have led to the development of adapted safety devices. Hydrogen is a very small molecule that is difficult to keep concentrated within a confined space and disperses quickly in the event of a leak. But today, the systems are viable and it is safe to drive a hydrogen-powered car. When I travel abroad to represent the CNRS, hydrogen is widely seen as the energy vector of the future for many applications.
I am excited about the future of this solution. I believe that hydrogen will grow exponentially in the years to come, both as a storage, mobility and heating solution. In France alone, its deployment is accelerating with the introduction of the Hype taxis in Paris, the Navibus in Nantes and the launch of hydrogen mobility plans in several regions. These are not isolated examples: all over the world, recognition and implementation of this solution is gaining ground – something that fills me with enthusiasm!