A New, More Economical, Cleaner, and More Convenient Method of Hydrogen Gas Production

nouveau procédé production hydrogène

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This new process, baptized CAPER (for Caustic Aqueous Phase Electrochemical Reforming) makes it possible to produce very pure hydrogen gas at high pressure, from ethanol in the aqueous phase. This approach requires lower temperatures and electrical voltages than traditional methods. Thus the conversion system can be implemented directly in service stations, eliminating the safety problems (and costs) associated with transporting and storing hydrogen at high pressure.

This method developed by researchers at Washington State University may finally help popularize the use of hydrogen as a clean fuel. Hydrogen fuel cell cars are indeed one of the solutions being considered to reduce transport-related CO2 emissions, as hydrogen fuel cells only produce water. But despite the environmental benefits of this technology, it struggles to establish itself for several reasons.

Hydrogen production costs are too high today. The process most commonly used today is steam reforming, which consists of dissociating molecules of methane (natural gas) using superheated steam. Dihydrogen and CO2 are then obtained (the latter requiring a capture and storage device). Hydrogen can also be produced by electrolysis of water (which decomposes into O2 and H2) – a method, however, less profitable, due to the amount of electricity required for this electrolysis. Added to this are the costs of transporting the compressed hydrogen to get it to the distribution points.

Compression performed upstream

The approach proposed by Professor Su Ha and his team can solve all of these problems. Their method requires only a small amount of electricity and a mixture of ethanol (C2H5OH) and water. ” It’s a new way of thinking about how to produce hydrogen gas. If there are enough resources, I think it has a very good chance of having a big impact on the hydrogen economy in the near future. “, underlines the scientist in a press release.

The CAPER process makes it possible to produce ready-to-use hydrogen gas at low energy cost. © BL Kee et al.

Their conversion system uses an anode and a cathode, immersed in a mixture of ethanol and water, to which a catalyst is added. The electrochemical reaction produces pure compressed hydrogen directly, while the carbon dioxide from the reaction is captured by the caustic electrolyte solution. The team reports a Faraday efficiency (the ratio between the amount of gas produced and the amount of gas theoretically produced during electrolysis) of 100%.

The method uses less than half the electricity needed to electrolyze pure water, the team says. ” The presence of ethanol in water changes the chemistry. We can actually carry out our reaction at a much lower electrical voltage than is typically required for electrolysis of pure water. “says Wei-Jyun Wang, co-author of the article. Another advantage of the CAPER process: all the compression is carried out on the reactants in the liquid phase (the ethanol + water mixture) to avoid less efficient (and much more energy-consuming) gas phase compression.

A process that provides an energy-efficient alternative to water electrolysis and can efficiently capture carbon dioxide while producing compressed hydrogen could have a significant impact on the hydrogen economy said Benjamin Kee, co-author of the article.

A whole supply chain already in place

The system also does not require an expensive membrane, unlike other water separation methods. Indeed, some existing technologies are based on proton exchange membrane electrolysers — an extremely thin polymer membrane, gas-tight, but which allows H ions to pass through.+. The electrodes are then arranged on either side of this polymer material. This approach involves the use of very expensive materials.

The CAPER process therefore truly makes it possible to produce hydrogen at a lower cost. With this method of production, only the ethanol will have to be transported to the supply stations; manufacturing can then be done on site, on demand and in complete safety. Ethanol is rich in hydrogen and can be easily obtained in large quantities (notably via the fermentation of renewable resources). Furthermore, the supply chain for ethanol is already in place (since gasoline containing ethanol is already distributed at all service stations).

Like electric cars, a hydrogen fuel cell car does not emit carbon dioxide. But unlike electric vehicles, it has the advantage of being able to be refueled in just a few minutes (against sometimes several hours of recharging for the batteries). Especially since the hydrogen resulting from the electrochemical reaction is here ready for use.

The researchers are now trying to evolve their technology and make it work continuously. They are also working on using the carbon dioxide produced during the reaction and captured in the liquid.

Source: BL Kee et al., Applied Catalysis A: General