Directly Grow Ultrasmall Co2P QDs on MoS2 Nanosheets to Form Heterojunctions Greatly Boosting Electron Transfer toward Hydrogen Evolution

A green process to produce an efficient and inexpensive electro-catalyst toward hydrogen evolution reaction (HER) is of importance for hydrogen energy. Here, an efficient HER electrocatalyst is made by electrochemically depositing Co2P quantum dots (QDs) on MoS2-carbon cloth (Co2P QDs/MoS2-CC). Due to the MoS2 porous structure, similar to 3 nm Co2P QDs uniformly deposit on MoS2. The produced unique 3D-structured Co2P QDs/MoS2-CC not only prevents an agglomeration of the active material and improves the diffusion rate of H2 but also renders large accessible surface area and hierarchical pores for high-density reaction sites and enhanced mass transport rate. Experimental results and theoretical analysis of this unique heterostructure indicate that the evolution process of hydrogen is dominated by proton adsorption, and the introduction of sufficient edge active sites can significantly promote the HER. As a consequence, the hierarchical Co2P QDs/MoS2-CC electrocatalyst affords an ultra-low overpotential (41 mV at a current density of 10 mA cm-2) that ranks the best among all reported MoS2 HER catalysts and exhibits excellent durability in 1 M KOH solutions, thus holding great promise for the practical application while shedding on fundamentals to nanoengineering an efficient electrocatalyst.