Date/Time
Date(s) - 15/07/2021
1:30 pm - 2:30 pm

Title:                     Preparation and application of oxide doped conductive molybdenumdisulfide 

Date:                    Thursday, July 15, 2021

Time:                    1:30 p.m.  

Zoom:                    available on request – macchem@mcmaster.ca

Host:                    Dr. Peter Kruse 

Abstract:                    

For applications of MoS₂ in batteries,supercapacitors, electrocatalysts solar cells and water quality sensors, asubstantially increased conductivity is required in order to achieve reasonablecurrents. Popularly, the metallic 1T-MoS₂ phase is used, which canbe prepared via a lithium intercalation process, requiring inert atmosphereprocessing and safety procedures.

Here we demonstrate a safer and more efficient processto yield conductive MoS₂ (c-MoS₂). This simple andeffective way to prepare few layers c-MoS₂ utilizes ambientconditions and 0.06 vol% aqueous hydrogen peroxide. Part of the research efforthas been to enhance the conductivity of MoS₂ using the idea of greensolvent (like pure water). The bulk conductivity of both peroxide and waterexfoliated MoS₂ are up to seven orders of magnitude higher than thatof the semiconducting 2H-MoS₂ phase. The samples were characterizedwith Hall measurements, X-ray photoelectron spectroscopy (XPS) and Ramanspectroscopy. Trace amounts of hydrogen molybdenum bronze (H_xMoO_3-y)and sub stoichiometric MoO_3-y were shown to help tune theconductivity of the nanometer-scale thin films without impacting thesulfur-to-molybdenum ratio. c-MoS₂ was further functionalized withthiols to determine the number of residual reactive sites. We also study themechanism of surface functionalization of MoS₂ with diazoniummolecules (both direct and in-situ approach) to understand the surface propertyof our material.

An important goal of our work is to control theconductivity of the MoS₂ thin films in safe and facile ways thatenable their application in low-cost chemiresistive sensors in liquidenvironments. We fabricated chemiresistive sensors with centimeter channel lengthswhile maintaining low measurement voltages for pH and metal cation sensing. Wefurther measured the catalytic activity of c-MoS₂ films in 0.5 M H₂SO₄electrolyte solution using linear sweep voltammetry (LSV) which showed a lowerTafel value at 10 mA/cm² current density. The lower Tafel valuedemonstrated that c-MoS₂ has potential to use as catalyst forhydrogen evolution reaction. Our study furthers the understanding of conductiveforms of MoS₂ and opens up a new pathway for next generationelectronic and energy conversion devices.