C&CB Seminar – Dipankar Saha , Chemistry
Jul 15, 2021
1:30PM to 2:30PM
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 – firstname.lastname@example.org
Host: Dr. Peter Kruse
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 (HxMoO3-y)and sub stoichiometric MoO3-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.