Water Spillover to Expedite Two‐Electron Oxygen Reduction

Abstract

AbstractLimited by the activity‐selectivity trade‐off relationship, the electrochemical activation of small molecules (like O2, N2, and CO2) 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 O2 to hydrogen peroxide (H2O2). 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 H2O2 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 cm2, in combination with techno‐economics simulations showing H2O2 production cost strongly dependent on current densities, giving the lowest H2O2 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.