Covalent organic frameworks with Ni-Bis(dithiolene) and Co-porphyrin units as bifunctional catalysts for Li-O 2 batteries

Abstract

The rational design of efficient and stable catalysts for the oxygen reduction reaction and oxygen evolution reaction (ORR/OER) is the key to improving Li-O 2 battery performance. Here, we report the construction of ORR/OER bifunctional cathode catalysts in a covalent organic framework (COF) platform by simultaneously incorporating Ni-bis(dithiolene) and Co-porphyrin units. The resulting bimetallic Ni/Co-COF exhibits high surface area, fairly good electrical conductivity, and excellent chemical stability. Li-O 2 batteries with the Ni/Co-COF–based cathode show a low discharge/charge potential gap (1.0 V) and stable cycling (200 cycles) at a current density of 500 mA g −1 , rivaling that of PtAu nanocrystals. Density functional theory computations and control experiments using nonmetal or single metal–based isostructural COFs reveal the critical role of Ni and Co sites in reducing the discharge/charge overpotentials and regulating the Li 2 O 2 deposition. This work highlights the advantage of bimetallic COFs in the rational design of efficient and stable Li-O 2 batteries.