Nature Energy, Published online: 26 June 2026; doi:10.1038/s41560-026-02094-7

Alkaline water electrolysers are being optimized for higher performance, but measures such as advanced electrodes or thinner separators can increase hydrogen crossover and safety risks. Here the authors analyse crossover behaviour and show that a gas recombination catalyst cuts crossover by 95% without affecting electrolyser performance.