Plasma-Chemical Integration of Solution-Derived ATTT with 3D Carbon Nanowalls for Controllable WS ₂ /WO x Hybrid Supercapacitor Electrodes

High Resolution Image Download MS PowerPoint Slide Two-dimensional (2D) tungsten disulfide (WS 2 ) has attracted considerable interest as a pseudocapacitive material, yet its practical application is often hindered by limited electrical conductivity, complex fabrication routes, and the need for binders. Here, we report a plasma-chemical route for fabricating binder-free, composition-tuned WS 2 /WO x @CNW hybrid electrodes from solution-deposited ammonium tetrathiotungstate (ATTT) with a downstream hydrogen remote plasma process. By systematically varying the ATTT concentration and microwave power, the surface chemistry of the CNW scaffold is controllably routed into CNW-dominant, WS 2 -rich, S-oxide-rich, and WO x -dominant regimes while preserving the overall three-dimensional CNW framework, despite partial surface masking at high oxide coverage. Structural and chemical analyses reveal that incomplete plasma conversion at high ATTT and low power leaves sulfur-rich species that are prone to oxidation, whereas high power promotes sulfur-vacancy formation and W-rich surfaces that preferentially evolve into WO x upon air exposure. Electrochemical measurements demonstrate that introducing WS 2 /WO x functionalities markedly enhances areal capacitance relative to bare CNWs. The WO x -dominant electrode delivered the highest areal capacitance among the tested electrodes, 91.1 mF cm –2 at 0.1 V s –1 and 21.7 mF cm –2 at 1.0 V s –1, compared with 4.6 and 3.15 mF cm –2 for bare CNW, respectively, although this gain was accompanied by increased interfacial and transport resistance. Dunn and impedance analyses reveal that this improvement arises primarily from increased diffusion-controlled pseudocapacitive charge storage, accompanied by a trade-off in the form of higher interfacial and transport resistance. This work elucidates how precursor loading and hydrogen-radical flux govern competitive sulfur- versus tungsten-centered oxidation pathways and provides a practical plasma-chemical framework for engineering high-performance, binder-free WS 2 /WO x @CNW hybrid electrodes for supercapacitor applications.