Plasma-Treated 1D Transition Metal Dichalcogenides for Efficient Hydrogen Evolution Reaction

Significant research endeavours have been dedicated to the search for highly efficient and cost-effective electrocatalysts for the Hydrogen Evolution Reaction (HER). Tungsten disulphide (WS₂) nanotubes were previously demonstrated for electrocatalysis performances owing to their unique chemical structure and physical properties. In this study, we report a new method of surface modification through cold radiofrequency (RF) plasma. The effect of two plasmatic ions (D₂⁺ and Ar⁺) on WS₂ nanotubes has been investigated. The plasma-treated samples showed improved performances in HER electrocatalysis. Based on experimental results, both Ar and D₂ plasma treatments, when performed separately, show similar effects on electrocatalysis performances with improved HER overpotentials of 348 and 343 mV at -10mA/cm² compared to 567 mV of the pristine WS₂ nanotubes. On the other hand, combined treatment by Ar and then by D₂ radio frequency plasma notably decreases the overpotential to 264 mV.<br/>Hydrogen is considered a promising alternative for energy production due to its high energy density, high calorific value, and zero environmental effect of combustion products. To avoid the risk of the continuous exploitation and increased consumption of fossil fuels, the efficient and sustainable electrocatalysts for HER is required.<br/>Among all the known HER catalysts, Pt-group metals have been utilized as the most effective electrocatalysts for HER in an acidic medium. However, the low abundance and high cost considerably limit its large-scale application. The preferred electrocatalyst material should lower the activation energy so the process consumes less energy at fast reaction kinetics of the HER.<br/>Two-dimensional transitional metal dichalcogenides (TMDs) are an emerging class of materials with advantageous properties for a wide range of applications such as nanoelectronics, nanophotonics, sensing, etc. Due to the very distinctive characteristics such as robustness, low cost, ease of intercalation, and accessibility to structural modification, this group of compounds exhibit excellent electrochemical characteristics. WS₂ is a representative member of the TMD family. One-dimensional (1D) WS₂ nanotubes are extensively studied for their unique structural and electronic properties. Among other applications, WS₂ nanotubes demonstrated efficient catalytic performance for HER. WS₂ nanotubes feature unique physical and chemical behavior originating from the lattice strain raised by the tubular curvature. Yet, this specific class of pristine inorganic nanotubes possesses fewer active sites and thus eventually suffers from the low affinity of WS₂ nanotubes for proton adsorption. Among different methods, plasma treatment was reported to modify the surface of WS₂ nanoparticles effectively. Low-power RF plasma treatment increases the number of disordered sites at the surface layer and produces atom vacancies, thus significantly enhancing energy conversion performance. Herein, we demonstrate the surface modification of WS₂ nanotubes by plasma treatment. This plasma modified WS₂ nanotubes used as catalyst reveal improved HER performance.<br/>To summarise, we have successfully formed plasma-treated WS₂ nanotubes, which provides a high concentration of active catalytic sites for electrocatalytic reaction. As a result, the HER catalytic activity of all the treated samples significantly improved compared to pristine WS₂ nanotubes. Plasma treatment induces material modification by creating defects and disorders of the nanotube surface. Additionally, RF plasma treatment helps the incorporation of oxides hydrophilic groups inside the system, which promotes fast electron transfer. The effective lowering of overpotential for HER activity was achieved due to the simple, scalable, cost-effective, and less time-consuming plasma treatment on of the semiconductive WS₂nanomaterial, demonstrates efficient and stable HER electrocatalytic performance.