Three-dimensional hierarchical flowers-like cobalt-nickel sulfide constructed on graphitic carbon nitride: Bifunctional non-noble electrocatalyst for overall water splitting

Tailoring various micro-nano structured materials by employing different techniques to enhance their porosity and conductivity has captivated significant consideration, making their remarkable electrochemical properties accessible within the area of energy storage devices. Herein we report the impact of graphitic carbon nitride concentration (0.03 ∼ 0.1 g) on nickel-cobalt sulfide morphologies and performance in hydrogen production. Employing the facile hydrothermal method, a cubic crystalline nickel-cobalt sulfide was stabilized on defective layered graphitic carbon nitride nanosheets for overall water splitting. A performance peak was observed in a sample with a graphitic carbon nitride concentration of 50 mg, which not only prevented the agglomeration but also provided a porous structure for enhanced gas diffusivity and charge transfer rates owing to the synergistic Carbon and Nitrogen bonding with Cobalt and Nickel Sulfide. Optimized concentration of graphitic carbon nitride also increased the electrocatalytic active surface area threefold when compared with nickel-cobalt sulfide. The fabricated well-aligned flower-like pattern CoNi2S4/graphitic carbon nitride (50 mg) delivered a low overpotential of 310 mV and 160 mV for oxygen evolution reactions and hydrogen evolution reactions to reach a current density of 30 mA/cm2 and 10 mA/cm2 in alkaline media. The electrolyzer displayed an electrolysis potential of 1.58 V to reach 10 mA/cm2 current density with the long-term durability of 24 h. This strategy depicts a novel approach for utilizing this renowned nickel-cobalt sulfide with graphitic carbon nitride catalyst for the application of alkaline electrocatalytic water splitting.