Tailoring N and S Heteroatoms Through Rational Design in Carbon Nanotubes-Graphene Composites for Enhanced Zn-Air Battery Performance.

Abstract

Cathodic materials significantly influence the performance, durability, and sustainability of primary zinc-air batteries (ZABs). This study focuses on the rational design of highly active metal-free composites by tailoring the content of N and S heteroatoms in carbon nanotube-graphene (CNTG) composites. The oxygen reduction reaction (ORR) tests showed onset potentials (E_o) of 0.88 V (N-CNT) and 0.89 V (N-graphene) for individual materials and 0.92 V for the N-CNTG composite, highlighting the advantage of using a composite materialThe N content varied with dicyandiamide and urea, displaying changes in the surface area and N content (7.09 vs. 5.30 at. %), and in pyridinic and quaternary N species. The N content varied with dicyandiamide and urea, showing changes in the surface area and N content (7.09 vs. 5.30 at. %), and in pyridinic and quaternary N species. The abundance of pyridinic-N species in N-CNTG using urea enabled a higher ORR activity (E_o=0.92 V). The S incorporation through thiourea improved the E_o to 0.94 V (Pt/C=1.03 V). And, the combination of urea and thiourea resulted in a highly active and durable N,S-CNTG material, displaying a E_o of 0.96 V, and an activity loss of 8.7 % (Pt/C=25.4 %) after 2000 cycles. In ZAB mode, this material displayed a voltage of 1.35 V, a power density of 107 mW cm^-2, and a specific capacity of 1060 mA h g^-1.