N,S‐Doped Zeolite‐Templated Carbon Like Supported Ni_xFe_yS_z as an Efficient Bifunctional Catalyst for Rechargeable Zinc Air Batteries

Abstract

A still unexplored class of heterostructured bifunctional catalysts for oxygen evolution (OER) and reduction (ORR) reactions is investigated: Ni‐Fe sulfides deposited onto a N,S‐co‐doped zeolite‐templated carbon (ZTC) substrate achieved upon the impregnation of a ZTC with thiourea and Ni and Fe precursors (Ni/Fe atomic ratio of 1). By heat‐treating the impregnated ZTC substrate at 700 °C under N2 atmosphere the efficient bifunctional catalyst is generated. A difference of only 0.76 V is measured between the potential required to drive an OER current density of 10 mA cm‐2 and the ORR half‐wave potential. Using electrochemical measurements and physico‐chemical characterizations, it is evidenced that OER activity results from the presence of a sulfide containing both Fe and Ni whereas the ORR activity originates from the N,S‐doped ZTC substrate. The selectivity of the ORR process is improved through the presence of sulfide phases. Compared to more conventional carbon substrate such as N,S‐co‐doped reduced graphene oxide, high specific surface area ZTC favors high ORR performances. The functional ZTC material was further successfully implemented as bifunctional air electrode in a coin‐type Zn‐air battery.