Enhanced oxygen reduction from the insertion of cobalt into nitrogen-doped porous carbons

Abstract

This work addresses unprecedentedly enhanced electrocatalytic activity of oxygen reduction reaction (ORR) by potassium hydroxide (KOH) chemical activation and cobalt doping of nitrogen-doped porous carbon (NPC). Polyacrylonitrile (PAN) and cobalt acetate are used as carbon–nitrogen and cobalt precursors to synthesize the cobalt-doped NPC. The KOH activation primarily enhances the activity of NPCs in the ORR by making them highly porous and forming pyrrolic nitrogen in the carbon network. It is the subsequent cobalt doping process that not only induces more transitions of pyridinic to pyrrolic nitrogen but also generates new active sites of oxide and carbide forms (Co₃O₄ and Co_xC) on the NPCs. A further reduction of hydrogen peroxide can occur on the cobalt-doped NPCs leading more favorably to the four electron pathway. The cobalt-doped NPC has an ORR activity comparable to the commercial Pt catalyst, but it shows higher stability and greater tolerance to methanol poisoning.