Amorphous MoSx-coated TiO2 nanotube arrays for enhanced electrocatalytic hydrogen evolution reaction

Two-dimensional amorphous MoSx (a-MoSx) has been confirmed to be a highly active and economic electrocatalyst for hydrogen evolution reaction (HER). The development of its hybrid cocatalyst is envisioned to bestow more active sites with appropriate crystal engineering and modified electronic properties for enhancing catalytic performance. In this work, a composite cocatalyst comprising a-MoSx (x = 1.78) and well-ordered anodized TiO2 nanotube arrays (TNAs) is successfully developed through a facile electrodeposition route. The synergistic coupling of the unique vector charge transfer effect of TNAs and proliferation of active sites in a-MoSx derived from the space confinement effect and curved interface growth of TNAs lead to a significant enhancement of HER activity, compared to those of other forms of MoS2-based electrodes that have been previously reported. The MoSx/TNAs electrode exhibits the relatively small onset overpotential of 88 mV and presents an overpotential of 157 mV at 10 mA cm-2 HER current density. The composite electrodes also show an excellent stability with no performance degradation after undergoing 1000 times successive linear sweep voltammetry. The deposition of a-MoSx onto the curved sidewall in a confined space of TNAs is demonstrated to be an effective method to induce the growth of a-MoSx, leading to an enhanced catalytic activity toward HER.