Co₃O₄ Nanocube-Templated CoS₂ and CoS₂/MoS₂ Heterostructures for Multifunctional Electrocatalysis

Thedesign and development of efficient and low-cost electrocatalystsfor both anodic (oxygen evolution reaction (OER)/hydrazine oxidationreaction (HzOR)) and cathodic (hydrogen evolution reaction (HER))reactions are the major challenges for cleaner hydrogen production.Especially, the fabrication of electrocatalysts with abundant electrochemicallyactive sites through simple synthetic routes is of great interestto draw excellent catalytic efficiency. This report provides a strategyto prepare CoS2-MoS2 heterostructuresand spheroid-like CoS2 through the sulfurization reactionfrom the common Co3O4 nanocube precursor inthe presence and absence of the molybdenum precursor, respectively.The as-prepared CoS2-MoS2 (25) heterostructure(prepared with 25 mg of Co3O4) shows excellentHER activity in 1 M KOH by delivering a current density of 10 mA/cm(geo) (2) at an overpotential of 92.5 & PLUSMN; 3.1 mV.The observed enhancement in the HER activity is attributed to theimproved water dissociation kinetics at the abundant interfacial areashared between the two components of the heterostructure. Besides,spheroid-like CoS2 shows good OER and hydrazine oxidationreaction (HzOR) activity owing to the high electrochemically activesurface area. In addition, the alkaline electrolyzer (HER//OER) constructedusing the CoS2-MoS2 (25) heterostructureand spheroid-like CoS2 as the cathode and anode, respectively,delivers a current density of 10 mA/cm(geo) (2) ata cell potential of 1.67 V. Furthermore, the hydrazine-assisted electrolyzer(HER//HzOR) displays a low cell potential of 0.53 V to attain thesame current density along with excellent durability up to 30 h.