Cobalt layered double hydroxide nanosheets synthesized in water–methanol solution as oxygen evolution electrocatalysts

Abstract

Cobalt-based layered double hydroxides (Co-based LDHs) are cost-efficient electrocatalysts toward the oxygen evolution reaction (OER) associated with the conversion of clean and renewable energy. Herein we report a facile method for the in situ synthesis of monometallic Co LDH ultrathin nanosheets (UTNSs) through a one-step reaction between cobalt(II) nitrate and 2-methylimidazole (2MI) in water–methanol solution without the pre-synthesis of zeolitic imidazolate framework-67 (ZIF-67). The as-prepared Co LDH UTNSs possess atomic thickness, abundant oxygen vacancies and three-dimensional (3D) porous features. The best sample exhibits an outstanding OER performance on a glassy carbon electrode (GCE) with an overpotential (η) of 340 mV at 10 mA cm⁻², a Tafel slope of 56 mV dec⁻¹ and a turnover frequency (TOF) of 0.801 s⁻¹ at η = 350 mV in 1 M KOH. A two-electrode cell with the Co LDH UTNSs as the anode catalyst and commercial Pt/C as the cathode catalyst achieves a current density of 10 mA cm⁻² at the applied voltage of 1.625 V during the long-term electrolysis test. This work demonstrates a novel strategy based on water–methanol solution which is promising for the design and synthesis of ultrathin LDHs as highly active and stable catalysts applied in clean energy production.