Electrocatalytic Performance of Titania Nanotube Arrays Coated with MoS₂ by ALD toward the Hydrogen Evolution Reaction

Abstract

The electrochemical splitting of water provides an elegant way to store renewable energy, but it is limited by the cost of the noble metals used as catalysts. Among the catalysts used for the reduction of water to hydrogen, MoS 2 has been identified as one of the most promising materials as it can be engineered to provide not only a large surface area but also an abundance of unsaturated and reactive coordination sites. Using Mo[NMe 2 ] 4 and H 2 S as precursors, a desired thickness of amorphous MoS 2 can be deposited on TiO 2 nanotubes by atomic layer deposition. The identity and structure of the MoS 2 film are confirmed by spectroscopic ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrocatalytic performance of MoS 2 is quantified as it depends on the tube length and the MoS 2 layer thickness through voltammetry, steady-state chronoamperometry, and electrochemical impedance spectroscopy. The best sample reaches 10 mA/cm 2 current density at 189 mV overpotential in 0.5 M H 2 SO 4 . All of the various geometries of our nanostructured electrodes reach an electrocatalytic proficiency comparable with the state-of-the-art MoS 2 electrodes, and the dependence of performance parameters on geometry suggests that the system can even be improved further.

Atomic Layer Deposition of 2D Metal Dichalcogenides for Electronics, Catalysis, Energy Storage, and Beyond

“…100-200 nm) FET [226] 95 7.5-20 nm films (amorp.) HER [227] 80 (300-800, S) ≈10 nm films (as-dep. amorp., ann.…”

“… The measurements were performed in aqueous 0.5 m H 2 SO 4 solution except for 0.1 m H 2 SO 4 in a single study. [ 223 ] Either platinum [ 105,191,222,223,227,266,268,269 ] or graphite [ 211,213,214,228,275 ] counter electrode was used …”

“…Cao et al. [ 227 ] deposited amorphous MoS 2 films on TiO 2 nanotubes using Mo(NMe 2 ) 4 and H 2 S at 95 °C. The excellent HER performance, including a low η 10 of 189 mV and stable operation for 36 h, was attributed to the amorphous nature of the films as well as to the large surface area of the nanotubular substrate.…”

“…GC 394 122 -2019 [269] W [269] The measurements were performed in aqueous 0.5 m H 2 SO 4 solution except for 0.1 m H 2 SO 4 in a single study. [223] Either platinum [105,191,222,223,227,266,268,269] or graphite [211,213,214,228,275] counter electrode was used. a) For brevity, inert components (N 2 , Ar) of reactive atmospheres are omitted; b) The current densities are defined with respect to the projected (geometric) surface areas of the electrodes, i.e., they do not account for the specific surface areas of the substrate or film; c) High surface area substrate; d) Overpotentials using a low-density foam substrate with a lower surface area were higher as shown in Figure 14g.…”

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

“…Therefore, FXBID could be useful for the functionalization of porous substrates or buried structures with the only limitation that the precursor gas has to reach the intended deposition zone. Deposition in the depth of (nano)porous substrates is a common task in recent atomic layer deposition (ALD) studies targeting on highly reactive catalysts or absorbing agents with extra-large surfaces [120][121][122][123][124][125][126]. FXBID could also be used in terms of a photon assisted ALD process and contribute to increased functionalization rates, deposition from otherwise too stable precursors and spatially confined functionalization.…”