Simple activation effect on the EC hydrolysis performance of MOF structure

Abstract

Transition metal-based metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) are considered as the ideal substitutes or supports for electrochemical catalysis field. However, due to the limited number of surface-active sites and the low conductivity of the bulk of MOFs/COFs, their electrocatalytic (EC) performance is usually promoted by the complicated multi-step decoration procedures. In this paper, a simple sequential-activation-step was verified to have the ability to improve considerably the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance of pristine Co-MOF (ZIF-67) material. For example, NC@Co from the carbonized and electrochemical activated ZIF-67 exhibited enhanced OER properties, while NC@CoxOy obtained via a sequential carbonize-oxidized-electrochemical activated procedure on ZIF-67 exhibited outstanding HER performance relatively. Density Functional Theory (DFT) calculations indicated that the in situ generated CoOOH was attributed to the improved HER/OER performance of the corresponding ZIF-67 activated derivatives with the redistribution of electron density, increased conductivity, and the optimized adsorption Gibbs free energy of hydrolysis intermediates. This work presents potential directions for the application of MOFs or COFs in the fields of electrochemical energy conversion through the electrochemical pathways.