Design of hierarchical oxide-carbon nanostructures for trifunctional electrocatalytic applications

Abstract

The rational design of efficient trifunctional catalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is of significant importance for metal–air batteries and electrolyzers. Herein, a hierarchical carbon architecture that comprises of 1D tubes and 2D sheets supported on Ni–Co oxide is synthesized. The 1D–2D carbon nanostructures further support homogeneously dispersed Co/Ni–Nx centers, NiCo and its oxide nanoparticles that are beneficial for ORR, HER, and OER, respectively. The hierarchical nanostructures offer highly exposed surface that enables the maximum utility of active sites for different reactions and also provide a single platform that can be used as OER–ORR and OER-HER bifunctional catalyst for metal– air batteries and electrolyzers, respectively. The catalyst displays a low ΔE (EJ(OER) = 10 − E½(ORR)) of 0.846 V for bifunctional OER–ORR and low potential of 1.54 V at 10 mA cm−2 for overall water splitting with appreciable durability for 40 h. Overall, the nanostructures exhibit remarkable activity and are durable for OER, ORR, and HER. Moreover, the study offers a pathway to expand the functionality of the non-noble electrocatalyst and simultaneously offers a platform to prove that preferential active sites exist for different reactions.