Composites of a Prussian Blue Analogue and Gelatin-Derived Nitrogen-Doped Carbon-Supported Porous Spinel Oxides as Electrocatalysts for a Zn–Air Battery

To date, most studies have focused only on the interaction between oxygen and the catalyst, with the intention of minimizing the mass-transfer resistance by using the rotating disk electrode (RDE) method, which is based on the forced-convection theory. To begin with, in order to increase the reaction rate, the oxygen should be able to reach the active sites of the catalyst readily (mass transfer). Next, a moderate (i.e., not too strong or weak) interaction (kinetics) should be maintained between the oxygen molecules and the catalyst, in order to allow for better adsorption and desorption. Therefore, these two factors should be taken into consideration when designing electrocatalysts for oxygen reduction. Further, there is bound to be a demand for large-scale metal-air batteries in the future. With these goals in mind, in this study, a facile and scalable method is developed for fabricating metal-air batteries based on the fact that the Prussian blue analogue Mn₃[Co(CN)₆]₂•nH₂O and gelatin-coated Ketjenblack carbon thermally decompose at 400 °C in air (i.e., without requiring high-temperature pyrolysis under inert conditions) to form porous spinel oxides and N-doped carbon materials. The intrinsic kinetics characteristics and the overall performance of the resulting catalysts are evaluated using the RDE method and a Zn-air full cell, respectively.