Crumpled Transition Metal Dichalcogenide Sheets

Abstract

An electrohydrodynamic (EHD) method results in charge driven droplet fission and volumetric shrinkage of metal dichalcogenide sheet droplets, thus wrinkling individual exfoliated metal dichalcogenide sheets on the nanoscale. For example, the method can be used to activate the basal plane of solution exfoliated, stable 2H reverted sheets of MoS 2 . In this manner, the basal plane of 2H MoS 2 can be strained at an unprecedented scale (3.7%), resulting in charge transport to basal plane defects. The resulting crumpled MoS 2 integrates few layer sheets and atomistic defects with nano- and micro-scale ridges and vertices to enable centimeter-length films that elevate the catalytic site count of MoS 2 from 1.0×10 14 sites/cm 2 to 2.93×10 17 sites/cm 2 (planar 2H vs. crumpled 2H) and a turn-over-frequency (TOF) from 0.016 s −1 to 0.130 s −1.

We claim: 
     
         1 . A method of crumpling transition metal dichalcogenide sheets, comprising:
 forming an electrostatically charged liquid droplet comprising a plurality of planar sheets of a transition metal dichalcogenide;   applying a sufficient electric field to the droplet to cause the droplet to rupture into a plurality of fission droplets by an electrohydrodynamic process, wherein each fission droplet comprises at least one planar sheet of the transition metal dichalcogenide; and   evaporating the remaining liquid from the plurality of fission droplets, thereby inducing spontaneous self-crumpling of the at least one planar sheet of the transition metal dichalcogenide in each of the fission droplets.   
     
     
         2 . The method of  claim 1 , wherein the transition metal comprises molybdenum or tungsten. 
     
     
         3 . The method of  claim 1 , wherein the chalcogenide comprises sulfur, selenium, or tellurium. 
     
     
         4 . The method of  claim 1 , wherein the transition metal dichalcogenide comprises molybdenum disulfide. 
     
     
         5 . The method of  claim 4 , wherein the planar sheets of molybdenum disulfide comprise 2H phase sheets having basal plane defects and whereby the self-crumpling activates the basal plane defects. 
     
     
         6 . The method of  claim 1 , wherein the planar sheets of the transition metal dichalcogenide comprise exfoliated sheets. 
     
     
         7 . The method of  claim 1 , wherein the forming an electrostatically charged liquid droplet comprises feeding a solution of the planar sheets of the transition metal dichalcogenide through a spinneret. 
     
     
         8 . The method of  claim 1 , wherein the sufficient electric field is greater than approximately 1.25 kV/cm. 
     
     
         9 . The method of  claim 1 , wherein the evaporating comprises depositing the plurality of fission droplets on a substrate above a deposition temperature. 
     
     
         10 . The method of  claim 9 , wherein the substrate comprises a hydrogen evolution reaction substrate. 
     
     
         11 . The method of  claim 9 , wherein the substrate comprises carbon or silicon. 
     
     
         12 . The method of  claim 9 , wherein the deposition temperature is greater than 200° C. 
     
     
         13 . The method of  claim 9 , wherein the deposition temperature is greater than 250° C. 
     
     
         14 . A method for electrochemical hydrogen evolution, comprising exposing an aqueous electrolyte to a crumpled transition metal dichalcogenide in an electrochemical cell at a sufficient cell voltage to catalyze the electrolysis of water and evolve hydrogen.