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

ABSTRACT

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 NiFe ₂ O ₄ 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 NiFe ₂ O ₄ @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 NiFe ₂ O ₄ @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 NiFe ₂ O ₄ @CNH‐N‐P is 54 mW/cm ² and thus exceeds a benchmark catalyst composed of 20% Pt/C+RuO ₂ of 28 by 26 mW/cm ² . 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.