N-Co-O Triply Doped Highly Crystalline Porous Carbon: An Acid Proof Nonprecious Metal Oxygen Evolution Catalyst

In comparison with nonaqueous Li-air batteries, aqueous Li-air batteries are kinetically more facile and there is more variety of non-noble metal catalysts available for oxygen electrocatalysis, especially in alkaline solution. The alkaline battery environment is however vulnerable to electrolyte carbonation by atmospheric CO2 resulting in capacity loss over time. The acid aqueous solution is immune to carbonation but is limited by the lack of effective non-noble metal catalysts for the oxygen evolution reaction (OER). This is contrary to the oxygen reduction reaction (ORR) in acid solution where a few good candidates exist. We report here the development of a N-Co-O triply doped carbon catalyst with substantial OER activity in acid solution by the thermal codecomposition of polyaniline, cobalt salt and cyanamide in nitrogen. Cyanamide and the type of cobalt precursor salt were found to determine the structure, crystallinity, surface area, extent of Co doping and consequently the OER activity of the final carbon catalyst in acid solution. We have also put forward some hypotheses about the active sites that may be useful for guiding further work.