Bromide-mediated paired electrosynthesis of hydrogen and epoxide.

Water electrolysis struggles to compete with the low cost of hydrogen produced from methane or coal. We propose a bromide-mediated paired electrosynthesis system in which an aqueous electrolyte is combined with olefins in an inert organic co-solvent to simultaneously generate hydrogen and epoxides. In this process, bromide electrolysis first produces gaseous hydrogen and solution-confined bromine; the bromine is then used to partially oxidize olefins into high-value epoxides while being regenerated back to bromide. By replacing low-value oxygen with valuable epoxides, this approach increases the economic viability of water electrolysis and can be applied to a wide range of olefins. We demonstrate the concept using styrene, converting water and styrene into hydrogen and styrene oxide in a membraneless system with high efficiency, high rate, and high product selectivity.