Thermal suppression of charge disproportionation accelerates interface electron transfer of water electrolysis.

The sluggish electron transfer kinetics in electrode polarization driven oxygen evolution reaction (OER) result in big energy barriers of water electrolysis. Accelerating the electron transfer at the electrolyte/catalytic layer/catalyst bulk interfaces is an efficient way to improve electricity-to-hydrogen efficiency. Herein, the electron transfer at the Sr 3 Fe 2 O 7 @SrFeOOH bulk/catalytic layer interface is accelerated by heating to eliminate charge disproportionation from Fe 4+ to Fe 3+ and Fe 5+ in Sr 3 Fe 2 O 7 , a physical effect to thermally stabilize high-spin Fe 4+ (t 2g 3 e g 1 ), providing available orbitals as electron transfer channels without pairing energy. As a result of thermal-induced changes in electronic states via thermal comproportionation, a sudden increase in OER performances was achieved as heating to completely suppress charge disproportionation, breaking a linear Arrhenius relationship. The strategy of regulating electronic states by thermal field opens a broad avenue to overcome the electron transfer barriers in water splitting.