Alloys of Cobalt Grafted with CNT Supported on N-Doped Carbon Heterostructure As Bifunctional Electrocatalysts

Abstract

Development of eco-friendly, stable, and affordable electrocatalysts is crucial for the sustainable energy production and storage units such as fuel cells, water electrolysis, and metal–air batteries. Metal organic frameworks (MOFs) are class of compounds in which metal ions are coordinated to an organic ligand. They have emerged as a great precursor for the synthesis of various electrocatalysts for Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER).Carbon motifs derived from zeolitic imidazole frameworks (ZIFs), a subfamily of MOFs, have exceptional mechanical and chemical stability due to the presence of metal-nitrogen bonds. Amongst various synthesized ZIFs, ZIF-67 has cobalt ions (Co2+) coordinated to imidazolate-type linkers. The ZIF-67 derived carbon precursors are generally mesoporous, possess high degree of graphitization and large surface area.Herein, we have tried to immobilize noble metals like Pd, Pt and Ru with short CNTs grafted on C matrix named as PdCo@NC, PtCo@NC and RuCo@NC, respectively. [1] We have synthesized a series of electrocatalysts by a novel H2-free method using simple one-step pyrolysis. The as-synthesized catalysts show excellent bifunctional catalytic activity towards HER as well as OER in alkaline medium. The catalysts show long cycle stability and compete with the state-of-the-art electrocatalysts like RuO2 and Pt/C. PtCo@NC and RuCo@NC shows the best HER and OER, respectively. Further, the excellent electrocatalytic activity is explained based on a synergistic effect between the noble metal and ZIF-67 derived N-doped carbon support.