Water Spillover to Expedite Two‐Electron Oxygen Reduction

Abstract Limited by the activity‐selectivity trade‐off relationship, the electrochemical activation of small molecules (like O 2 , N 2, and CO 2 ) rapidly diminishes Faradaic efficiencies with elevated current densities (particularly at ampere levels). Nevertheless, some catalysts can circumvent this restriction in a two‐electron oxygen reduction reaction (2e − ORR), a sustainable pathway for activating O 2 to hydrogen peroxide (H 2 O 2 ). Here we report 2e − ORR expedited in a fluorine‐bridged copper metal–organic framework catalyst, arising from the water spillover effect. Through operando spectroscopies, kinetic and theoretical characterizations, it demonstrates that under neutral conditions, water spillover plays a dual role in accelerating water dissociation and stabilizing the key * OOH intermediate. Benefiting from water spillover, the catalyst can expedite 2e − ORR in the current density range of 0.1–2.0 A cm −2 with both high Faradaic efficiencies (99–84.9%) and H 2 O 2 yield rates (63.17–1082.26 mg h −1 cm −2 ). Further, the feasibility of the present system has been demonstrated by scaling up to a unit module cell of 25 cm 2 , in combination with techno‐economics simulations showing H 2 O 2 production cost strongly dependent on current densities, giving the lowest H 2 O 2 price of $0.50 kg −1 at 2.0 A cm −2 . This work is expected to provide an additional dimension to leverage systems independent oftraditional rules.