A novel alkaline air electrode based on a combined use of cobalt hexadecafluoro-phthalocyanine and manganese oxide

Abstract

Electrocatalytic reduction of O2 with dual catalysts of cobalt 1, 2, 3, 4, 8, 9, 10, 11, 15, 16, 17, 18, 22, 23, 24, 25-hexadecafluoro-29 H, 31H-phthalocyanine (CoPcF16) and MnOOH was studied in alkaline media with cyclic and rotating ring-disk electrode (RRDE) voltammetry. Cyclic voltammetric results show that CoPcF16 possesses a good catalytic activity for redox-catalyzing an apparent two-electron reduction of O2 with superoxide (O2−) as an intermediate. The combined use of CoPcF16 with MnOOH which shows a bifunctional catalytic activity toward the sequential disproportionations of the reduction intermediate and product, i.e. O2− and peroxide (HO2−), eventually enables an apparent four-electron reduction of O2 to be achieved at a positively-shifted potential in alkaline media. The possibility of utilizing the dual catalysts for the development of practical alkaline air electrodes was further explored by confining the catalysts in active carbon (AC) and carbon black (CB) matrices that are generally used as the substrate for constructing air electrodes. The RRDE voltammetric results suggest that an apparent four-electron reduction of O2 reduction can be obtained at the as-prepared carbon-based air electrode at a potential close to that at the Pt-based air electrode, and that the as-prepared electrode shows a high tolerance against methanol and glucose crossover.