Decoupled Water Splitting for Green Hydrogen Production at Scale

Green hydrogen produced by splitting water molecules into hydrogen and oxygen using renewable sources is expected to play a major role in the transition to carbon neutral economy, serving as an energy carrier that can facilitate the penetration of an higher share of intermittent renewable energy, the decarburization of hard-to-abate industrial sectors (e.g. industrial processes which require high- grade heating or rely on hydrogen as a feedstock) and the cross-sectorial coupling (linking power, gas and other energy vectors or energy intensive commodities and replacing them in their respective usages). The baseline technology for green hydrogen production is called water electrolysis, where renewable power is applied to break the chemical bonds in water molecules and produce hydrogen and oxygen simultaneously at two electrodes, cathode and anode, in alkaline or acidic solution. The coupled generation of hydrogen and oxygen at the same time in the same cell presents a safety risk, since the mixture of the two is highly flammable. Therefore, a membrane and sealing are used to isolate the electrodes from each other, which complicates cell construction and requires maintenance, both increasing the production cost of green hydrogen. In addition, severe (20-30%) energy losses, mostly due to the difficult reaction that evolves oxygen, increase the cost of energy in this energy intensive technology. These drawback present challenges for wide scale adoption of green hydrogen. In order to overcome these challenges, we develop an alternative technology that decouples the generation of hydrogen and oxygen into two stages, separated by time, or two cells, space separated, avoiding the need for membrane and sealing. In addition, we divide the oxygen evolution reaction, a difficult electrochemical reaction that requires four electrons to generate an oxygen molecule on an atomic reaction site, into two sub-reactions that occur on four sites instead of one, thereby enabling easier reactions and saving most of the losses in water electrolysis. An ultrahigh efficiency of nearly 99% was demonstrated at lab scale, and we expect reaching 95% at system scale. To bring this transformative concept to reality we established H 2 Pro, and Israeli company that aims to provide green hydrogen at scale based on our innovation. Speaker(s): Prof. Avner Rothschild, Bellevue, Washington, United States, Virtual: https://events.vtools.ieee.org/m/287954