High-efficiency Electroreduction of O2 into H2 O2 over ZnCo Bimetallic Triazole Frameworks Promoted by Ligand Activation

Abstract

Co-based metal-organic frameworks (MOFs) as electrocatalysts for two-electron oxygen reduction reaction (2e^- ORR) are highly promising for H₂ O₂ production, but suffer from the intrinsic activity-selectivity trade-off. Herein, we report a ZnCo bimetal-triazole framework (ZnCo-MTF) as high-efficiency 2e^- ORR electrocatalysts. The experimental and theoretical results demonstrate that the coordination between 1,2,3-triazole and Co increases the antibonding-orbital occupancy on the Co-N bond, promoting the activation of Co center. Besides, the adjacent Zn-Co sites on 1,2,3-triazole enable an asymmetric "side-on" adsorption mode of O₂ , favoring the reduction of O₂ molecules and desorption of OOH* intermediate. By virtue of the unique ligand effect, the ZnCo-MTF exhibits a 2e^- ORR selectivity of ≈100 %, onset potential of 0.614 V and H₂ O₂ production rate of 5.55 mol g_cat ^-1 h^-1 , superior to the state-of-the-art zeolite imidazole frameworks. Our work paves the way for the design of 2e^- ORR electrocatalysts with desirable coordination and electronic structure.

Keywords: Ligand effect; Two electron oxygen reduction; hydrogen peroxide; metal-organic framework; metal-triazole framework.