Insights into the regulation of interfacial charge distribution in ZnS@CoNi2S4 heterojunctions for high energy density supercapattery and efficient electrocatalytic water splitting applications

Herein, a facile approach for the design of dual high-efficacy supercapacitor electrode and efficient bidirectional electrocatalysts in electrolysis using hierarchical ZnS/CoNi₂S₄ (ZCNS) heterostructure was developed. Comprehensive experimental analysis unveiled that ZCNS heterostructure underwent a surface reformation, during electrochemical reactions, with an in-situ construction of Ni(OH)₂ and Co(OH)₂ onto ZnS@CoNi₂S₄ interface. As a result, the ZCNS heterostructure delivered a large specific capacity of 730.0 C g⁻¹ at 1 A g⁻¹ exhibiting a substantial cyclic stability. Consequently, the fabricated supercapattery device inherited a maximum energy density of 56.1 W h kg⁻¹ at a power density of 2100.1 W kg⁻¹ with a remarkable capacity of 289.0 C g⁻¹ at 3 A g⁻¹. Moreover, ZCNS electrocatalyst was exposed to be an impressive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalyst, which harvested the current rates of 10 and 50 mA cm⁻² under an overpotential of 170.1 mV for HER and 327.6 mV for OER with good durability in 1 M KOH, respectively. Additionally, the fabricated ZCNS||ZCNS device required only a lower potential of 1.61 V to drive a current rate of 10 mA cm⁻² for the complete electrolyzing process.