Controllable defect engineering based on cobalt metal-organic framework for boosting oxygen evolution reaction

Defect engineering on metal-organic frameworks (MOFs) provides high flexibility to rationally design advanced oxygen evolution reaction (OER) catalysts with low overpotential and high stability. However, fundamental understanding the effect of defect concentration on catalytic OER activity is still quite ambiguous. Herein, the CoMOF-Dx catalysts with regulated oxygen defects concentration are deliberately constructed via coupling one-pot solvothermal synthesis with NaBH4 chemical reduction process. Experimental findings propose that the oxygen defect concentration within Co-MOF-Dx gradually increases with raising the NaBH4 content, which could provide a flexible platform to tailor the electronic structure around active Co site and optimize adsorption/desorption capacity of oxygen intermediates. When the introduction content of NaBH4 is up to 5 mg, the resulting abundant unsaturated coordination defects could endow the Co-MOF-D5 catalyst with optimized electronic structure and more exposed active sites for improving charge transfer and adsorption/desorption capacity. It is found that the optimized Co-MOF-D5 can drive the current density of 10 mA cm-2 only at a low overpotential of 300 mV with the small Tafel slope of 53.1 mV dec �1 in alkaline medium. This work sheds light on the way for the development of high-performance MOF catalysts via modulating defect concentration.