Abstract
Fluorine and nitrogen codoped cobalt hydroxide-graphene oxide nanocomposites (N,F-Co(OH)(2)/GO) were synthesized by a simple hydrothermal method and demonstrated highly enhanced oxygen evolution activity in an alkaline medium. N,F-Co(OH)(2)/GO synthesized under optimized reaction conditions required an overpotential of 228 mV to produce the benchmark current density of 10 mA cm(-2) (scan rate 1 mV s(-1)). In contrast, N,F-Co(OH)(2) without GO and Co(OH)(2)/GO without fluorine required higher overpotentials (370 (N,F-Co(OH)(2)) and 325 mV (Co(OH)(2)/GO)) for producing the current density of 10 mA cm(-2). The low Tafel slope (52.6 mV dec(-1)) and charge transfer resistance, and high electrochemical double layer capacitance of N,F-Co(OH)(2)/GO compared to N,F-Co(OH)(2) indicate faster kinetics at the electrode-catalyst interface. The N,F-Co(OH)(2)/GO catalyst showed good stability over 30 h. High-resolution transmission electron microscope (HR-TEM) images showed good dispersion of polycrystalline Co(OH)(2) nanoparticles in the GO matrix. X-ray photoelectron spectroscopic (XPS) analysis revealed the coexistence of Co2+/Co3+ and the doping of nitrogen and fluorine in N,F-Co(OH)(2)/GO. XPS further revealed the presence of F in its ionic state and being covalently attached to GO. The integration of highly electronegative F with GO stabilizes the Co2+ active centre along with improving the charge transfer and adsorption process that contributes to improved OER. Thus, the present work reports a facile method for preparing F-doped GO-Co(OH)(2) electrocatalysts with enhanced OER activity under alkaline conditions.