Hydrogen could serve as a clean alternative to fossil fuels because, when used as a fuel, it produces water vapor instead of carbon dioxide (CO2). This cleaner fuel has proved particularly promising for the creation of so-called fuel cells, energy storage devices that could power heavy-duty vehicles, airplanes, trains and energy-intensive manufacturing machinery.
The leading approach for the scalable production of clean hydrogen relies on electrolyzers, electrochemical devices that can split water into hydrogen and oxygen. Some of the most promising electrolyzers developed so far are so-called liquid alkaline water electrolyzers (LAWEs), devices containing a liquid alkaline solution that can facilitate the movement of charged particles (i.e., ions) between the two electrodes where the desired chemical reactions occur.
In LAWEs, water molecules are converted into hydrogen at the cathode (i.e., negatively charged electrode) via the so-called hydrogen evolution reaction (HER). In contrast, oxygen gas is produced at the anode (i.e., positively charged electrode) via the so-called oxygen evolution reaction (OER).
In a LAWE, a component known as a separator ensures that the produced hydrogen and oxygen are kept apart while allowing ions to pass through. While this design is effective, some strategies used to boost the efficiency of LAWE hydrogen production can also result in more fuel passing through the separator and entering the oxygen-producing compartment. This poses serious safety risks, as some mixtures of hydrogen and oxygen can be flammable and explosive.
Researchers at Lawrence Berkeley National Laboratory and the University of California, Irvine, recently set out to better understand why this hydrogen crossover occurs and under what conditions. Their paper, published in Nature Energy, also introduces a new strategy that could help limit hydrogen leaks through the separator, improving the safety of LAWEs without compromising their efficiency.
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