  In this review, we discuss disruptive decoupled water splitting schemes, in
which the concurrent production of hydrogen and oxygen in close proximity to
each other in conventional electrolysis is replaced by time- or space-separated
hydrogen and oxygen production steps. We present the main decoupling
strategies, including electrolytic and electrochemical chemical water splitting
cycles, and the redox materials that facilitate them by mediating the ion
exchange between the hydrogen and oxygen evolution reactions. Decoupled water
splitting offers increased flexibility and robustness and provides new
opportunities for hydrogen production from renewable sources.
