Progress toward metal-air batteries: Mechanistic investigation of the effect of water on the oxygen reduction reaction at carbon-conductive polymer-silver composite air electrodes

The oxygen reduction reaction (ORR) at the carbon-conductive polymer-silver (C-cp-Ag) composite electrode in non-aqueous electrolyte with small amounts of added water is the subject of this study. The contributions of the various components of the composite electrode were assessed by employing four electrodes: (1) glassy carbon (C), (2) polypyrrole coated glassy carbon (C-cp), (3) silver disk (Ag), and (4) carbon-polypyrrole-silver composite (C-cp-Ag). Notably, with 5000 ppm of water in non-aqueous solution, the ORR reaction at Ag and C-cp-Ag shows an n = 4 reduction, while ORR at C and C-cp display an n = 1 reduction. The results show that the use of a multilayer C-cp-Ag composite electrode provides the opportunity to achieve the four electron reduction of one O₂ molecule, with a low precious metal (Ag) loading.