Comparison of catalytic activity of CoNi sulfide and Co-Ni sulfide/g-C3N4 nano-hybrids for overall water splitting

Abstract

Employing clean energy sources to produce hydrogen from the process of electrocatalytic water splitting has become one of the long-term solutions to the problems of depleting energy sources. To develop stable, efficient and non-noble electrocatalyst for water splitting is very crucial. Because of their low cost, pH stability and enhanced catalytic activity cobalt and nickel sulfide have become popular. But due to the problems of low surface area and higher over-potentials, the supplication of these sulfides is limited. To solve this problem different coupling techniques of these sulfides with highly active and porous materials have been employed. Advancing highly stable and active bifunctional transition metal sulfide-based electrocatalyst for water splitting is essential for fuel cell technology and the production of hydrogen. Herein, a three-dimensional hierarchical electrocatalyst in the form of flower pattern, aligning graphitic carbon nitride sheets with cubic crystalline Ni-Co sulfide on a nickel foam support, is introduced as a bifunctional electrocatalyst with an outstanding performance. CoNi2S4GCN heterostructure prepared by using a hydrothermal method to extend g-C3N4 porous layers, developed in higher catalytic activity for oxygen evolution and hydrogen evolution reactions with overpotentials of 310 mV and 160 mV to afford a current density of 30 mA/cm2 and 10 mA/cm2 . It is revealed that the astonishing features of this catalyst lie in the high porosity and surface area of conductive GCN support, the interfacial bonds between Carbon, nitrogen and cobalt, nickel sulfide and the three-dimensional configuration. The electrolyzer displays electrolysis at 1.58 V to reach a current density of 10 mA/cm2 with long term durability of 24 hours. This approach of preparing CoNi2S4GCN leads to enhanced kinetics for OER/HER, more exposed surface area, faster electron transport, enhanced diffusion of electrolyte and opened a new path of enhancing the catalytic activity of water splitting reactions.