In Situ Electrochemical Restructuring B-Doped Metal-Organic Frameworks as Efficient OER Electrocatalysts for Stable Anion Exchange Membrane Water Electrolysis.

Abstract

Metal organic frameworks (MOFs) are promising as effective electrocatalysts toward oxygen evolution reaction (OER). However, the origin of OER activity for MOF-based electrocatalysts is still unclear because of their structure reconstruction during electrocatalysis process. Here, a novel MOF (B-MOF-Zn-Co) with spherical superstructure is developed by hydrothermal treatment of zeolitic imidazolate framework-Zn, Co (ZIF-Zn-Co) using boric acid. The resultant B-MOF-Zn-Co shows high OER activity with a low overpotential of 362mV at 100mA cm-2 . Remarkably, B-MOF-Zn-Co displays excellent stability with only 3.6% voltage delay over 300h at 100mA cm-2 in alkaline electrolyte. Surprisingly, B-MOF-Zn-Co thoroughly transforms into B-doped CoOOH (B-CoOOH) during electrolysis process, which isserved as actual active material for high OER electrocatalytic performance. The newly-formed B-CoOOH possesses lower energy barrier of potential-determining step (PDS) for OOH* formation compared with CoOOH, benefiting for high OER activity. More importantly, B-MOF-Zn-Co based anion exchange membrane water electrolytic cell (AEMWE) demonstrates continuously durable operation with stable current density of 200mA cm-2 over 300h, illustrating its potential application in practice water electrolysis. This work offers an in situ electrochemical reconstruction strategy for the development of stable and effective OER electrocatalysts toward practice AEMWE.