Expediting in-Situ Electrochemical Activation of Two-Dimensional Metal–Organic Frameworks for Enhanced OER Intrinsic Activity by Iron Incorporation

Abstract

Electrochemical activation is an effective and simple method to obtain in-situ surface modification of MOF materials away from thermal decomposition. However, the impact of the rate and related phase transformation on OER intrinsic activity during the electrochemical activation process is often overlooked. Herein, we synthesized a kind of Co-MOF with a unique crystal structure in which the center metals were coordinated with the oxygen and nitrogen atoms from two water molecules and organic linkers. The bond strength between the center metals and the coordinated water molecules can be modulated by introducing Fe into Co-MOF, causing the expedited electrochemical activation. First-principles calculations suggest the electronic state of cobalt in CoFe-MOF can be modified to alter the free energy of adsorbed intermediates. Therefore, the obtained electrocatalyst possesses the optimal OER intrinsic activity, showing a low overpotential of 265 mV at 10 mA cm–2, a small Tafel slope of 44 mV dec–1, and a long-term electrochemical durability with a period of 40 h. The findings are expected to help understand the fundamental principles of electrochemical activation.