Nickelferrite on Pnictogen Functionalized Carbon Nanohorns. Bifunctional ORR and OER Catalysts in Rechargeable Zinc-Air Batteries.

In Nickel ferrites a low oxygen reduction activity and poor stability represent a drawback in rechargeable zinc-air battery technology. This contribution presents a strategy using self-templating for fabricating a nanohybrid material composed of NiFe2O4 nanocubes encapsulated in N, P-doped carbon nanohorns (CNH). Benefiting from the efficient mass and electron transfer of such N, P-doping, CNH provide a significant number of active sites preventing aggregation and dissolution of active ferrite components in the composite. Thus, the NiFe2O4@CNH-N-P nanohybrid catalyst exhibits a high half-wave potential (0.79 V) and a low Tafel slope of 56.5 mV/dec, following a four-electron pathway for oxygen reduction (ORR). The NiFe2O4@CNH-N-P nanohybrid catalyst work in full-cell zinc air battery configuration as bifunctional cathode catalyst in conjunction with a ZnO/C composite anode. The maximum power density derived from polarization curves for ZAB based on NiFe2O4@CNH-N-P is 54 mW/cm2 and thus exceeds a benchmark catalyst composed of 20% Pt/C+RuO2 of 28 by 26 mW/cm2. The assembled secondary ZAB can be cycled for more than 300 h in a galvanostatic charge-discharge test. This work provides insight into the rational composition and morphology design, as well as full materials and electrochemical characterization, of an earth-abundant electrocatalyst with efficient electrocatalytic activity.