title: Thickness Dependence and Percolation Scaling of Hydrogen Production Rate in MoS2 Nanosheet and Nanosheet-Carbon Nanotube Composite Catalytic Electrodes.
abstract: Here we demonstrate that the performance of catalytic electrodes, fabricated from liquid exfoliated MoS2 nanosheets, can be optimized by maximizing the electrode thickness coupled with the addition of carbon nanotubes. We find the current, and so the H2 generation rate, at a given potential to increase linearly with electrode thickness to up ∼5 μm after which saturation occurs. This linear increase is consistent with a simple model which allows a figure of merit to be extracted. The magnitude of this figure of merit implies that approximately two-thirds of the possible catalytically active edge sites in this MoS2 are inactive. We propose the saturation in current to be partly due to limitations associated with transporting charge through the resistive electrode to active sites. We resolve this by fabricating composite electrodes of MoS2 nanosheets mixed with carbon nanotubes. We find both the electrode conductivity and the catalytic current at a given potential to increase with nanotube content as described by percolation theory.
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: David
authors.initials: D
authors.lastname: McAteer
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Gholamvand
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Niall
authors.initials: N
authors.lastname: McEvoy
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Andrew
authors.initials: A
authors.lastname: Harvey
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Eoghan
authors.initials: E
authors.lastname: O'Malley
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Georg S
authors.initials: GS
authors.lastname: Duesberg
authors.affiliation: School of Physics, CRANN & AMBER, and ‡School of Chemistry, CRANN & AMBER, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Coleman
keywords: active sites; catalysis; edge; electrical resistance limited