Hydrophobic 3D Fe/N/S doped graphene network as oxygen electrocatalyst to achieve unique performance of zinc-air battery

Electrocatalysts’ activity in oxygen reduction reaction can be regarded as crucial indicator for their expected performance in metal-air battery, where catalyst selection is limited by low conductivity and insufficient electrochemical activity of available materials. This drawback could be addressed by the development of three-dimensional (3D) hierarchically structured carbon. In this study, hydrophobic 3D Fe/N/S doped graphene network is synthesized as electrocatalysts for zinc-air batteries in molten mixed salts (NaCl/FeCl2). It was observed that NaCl could seal maximum possible quantity of N in 3D-N/S. This is accompanied by more pyridinic-N and graphitic-N groups being tailor made in 3D-Fe/N/S. When assembled as air breathing cathodes in zinc-air batteries, 3D-Fe/N/S material demonstrated open-circuit potential (OCP) of 1.507 V, which was more than 1.492 V in case of 3D-N/S and 1.489 V of 20% Pt/C. Similar pattern occurred at discharge current density 50 mA cm−2 where a discharge voltage of 1.079 V observed in 3D-Fe/N/S was higher than 1.043 V of Pt/C and 1.040 V of 3D-N/S. Corresponding discharge power density maintained the same order, 3D-Fe/N/S (53.929 mW cm−2) > Pt/C (52.158 mW cm−2) > 3D-N/S (52.002 mW cm−2), rendering hydrophobic FeNx and N/S doped 3D-Fe/N/S better zinc-air battery electrode material than 20% Pt/C.