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

Abstract

The design and development of efficient and low-cost electrocatalysts for both anodic (oxygen evolution reaction (OER)/hydrazine oxidation reaction (HzOR)) and cathodic (hydrogen evolution reaction (HER)) reactions are the major challenges for cleaner hydrogen production. Especially, the fabrication of electrocatalysts with abundant electrochemically active sites through simple synthetic routes is of great interest to draw excellent catalytic efficiency. This report provides a strategy to prepare CoS2–MoS2 heterostructures and spheroid-like CoS2 through the sulfurization reaction from the common Co3O4 nanocube precursor in the presence and absence of the molybdenum precursor, respectively. The as-prepared CoS2–MoS2 (25) heterostructure (prepared with 25 mg of Co3O4) shows excellent HER activity in 1 M KOH by delivering a current density of 10 mA/cmgeo2 at an overpotential of 92.5 ± 3.1 mV. The observed enhancement in the HER activity is attributed to the improved water dissociation kinetics at the abundant interfacial area shared between the two components of the heterostructure. Besides, spheroid-like CoS2 shows good OER and hydrazine oxidation reaction (HzOR) activity owing to the high electrochemically active surface area. In addition, the alkaline electrolyzer (HER//OER) constructed using the CoS2–MoS2 (25) heterostructure and spheroid-like CoS2 as the cathode and anode, respectively, delivers a current density of 10 mA/cmgeo2 at a cell potential of 1.67 V. Furthermore, the hydrazine-assisted electrolyzer (HER//HzOR) displays a low cell potential of 0.53 V to attain the same current density along with excellent durability up to 30 h.