Electrocatalytic Performance of Titania Nanotube Arrays Coated with MoS 2 by ALD toward the Hydrogen Evolution Reaction.

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 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] and HS as precursors, a desired thickness of amorphous MoS can be deposited on TiO nanotubes by atomic layer deposition. The identity and structure of the MoS film are confirmed by spectroscopic ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrocatalytic performance of MoS is quantified as it depends on the tube length and the MoS layer thickness through voltammetry, steady-state chronoamperometry, and electrochemical impedance spectroscopy. The best sample reaches 10 mA/cm current density at 189 mV overpotential in 0.5 M HSO. All of the various geometries of our nanostructured electrodes reach an electrocatalytic proficiency comparable with the state-of-the-art MoS electrodes, and the dependence of performance parameters on geometry suggests that the system can even be improved further.