Core-shell-structured CoS2@N-doped carbon nanoneedle array as an efficient bifunctional electrocatalyst for overall water splitting

The development of environmentally friendly and highly effective electrocatalysts was crucial for boosting overall water splitting. Herein, a core-shell structured CoS2@N-doped carbon nanoneedle array grown on Ni foam (CoS2@N-ASC@NF) was directly constructed by a hydrothermal, soaking, and vacuum sulfurization approach. The representative core-shell structure constructed with large ECSA and small interfacial electron transfer resistance benefited the CoS2@N-ASC@NF to display improved electrocatalytic performance. The CoS2@N-ASC@NF displayed electrocatalytic activity toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a 1.0 M KOH with low overpotentials of 165.6 and 179.4 mV at 10 mA cm−2, respectively. Notably, the assembled electrolytic cell CoS2@N-ASC@NF||CoS2@N-ASC@NF showed low potentials of 1.430 and 1.646 V at 10 and 50 mA cm−2, respectively, which were better than those of RuO2||Pt/C (1.588 V at 10 mA cm−2 and 1.766 V at 50 mA cm−2), and also exhibited exceptional durability for 50 h continuous operation,. The synergism of core-shell structure, uniform nanoneedle array morphology and nitrogen doped carbon shell provided fast diffusion path for electrolyte ions, reduced the interfacial resistance and protect the core from corrosion to boost overall water splitting of CoS2@N-ASC@NF. This work provided us with a new insight into the design of carbon coated transition metal disulfide with good electrocatalytic activity and durability as bifunctional electrocatalyst in the fields of clean and sustainable energy.