Vertical and porous MoS2-CoS2 heterojunction nanosheet arrays as highly efficient bifunctional electrocatalysts for oxygen and hydrogen evolutions

Abstract

Highly efficient water electrolytic agents are restricted by the lack of cheap and Earth-abundant catalysts that can manipulate at unharsh conditions and be prepared with a simple procedure. Here, hierarchically vertical and porous MoS2-CoS2 heterojunction nanosheet arrays are designed and fabricated. The MoS2-CoS2 nanosheets are composed of ultrasmall nanocrytallites with the dimension of ∼62 nm. This special and novel architecture presents synergistic properties to create excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), where high density active sites generated by ultrasmall nanocrytallites with heterostructures, and the vertical and porous structure accelerates electrolyte transport with luxuriant channels while this hierarchically collaborative framework guarantees completely exposed active sites to electrolytes. This electrode shows low overpotentials of 295 and 103 mV at 10 mA cm−2, small Tafel slopes of 70 and 78 mV dec−1, and long stability for OER and HER, respectively. This work indicates that vertical and porous heterojunction nanosheet arrays with hierarchically ultrasmall secondary nanostructures are a promising catalyst for widespread application.