One-Pot Crystallization of 2D and 3D Cobalt-Based Metal–Organic Frameworks and Their High-Performance Electrocatalytic Oxygen Evolution

Abstract

Developing highly competent and low-cost earth-plentiful metal-based oxygen evolution reaction (OER) electrocatalysts is critical for future electrochemical conversion technologies and renewable energy systems. Herein, two cobalt-based metal-organic frameworks (Co-MOFs), [Co₆(btc)₂(DMF)₆(HCOO)₆] (2D, <b>MOF 1</b>) and [Co₃(CHOO)₉{DMA}₃] (3D, <b>MOF 2</b>), where btc = 1,3,5-benzenetricarboxylic acid, DMF = <i>N</i>,<i>N</i>-dimethylformamide, and DMA = dimethylamine, have been crystallized under hydrothermal conditions, from a single reaction. <b>MOF 1</b> shows an extraordinary OER performance with 175 mV overpotential to attain 10 mA cm^-2 current density with a low Tafel slope value of 80 mV dec^-1, whereas <b>MOF 2</b> achieves 10 mA cm^-2 current density at 389 mV overpotential. Two different architecture-based MOFs have been synthesized from a single solution for the very first time. Also, the OER activity of <b>MOF 1</b> overpowers the commercially used RuO₂ and surpasses most of the reported OER electrocatalysts. Post OER characterization of <b>MOF 1</b> revealed the in situ formation of Co(OH)₂ and CoOOH, acting as active sites for the OER process.