Operando insight into hydrogen crossover suppression by locking hydrophilic nanodomains in proton exchange membranes during water electrolysis.

Selective reconstruction of proton exchange membrane nanostructures can mitigate H2 crossover during water electrolysis. Operando small-angle X-ray scattering investigation demonstrates that membrane annealing prevents the expansion of hydrophilic nanodomains against changes in cell temperature and current density, thereby providing direct mechanistic insight into H2 crossover suppression.