Precise plasma engineering of Few-layer 1T-MoS 2 self-supported electrodes for bifunctional energy storage and electrocatalysis

The development of efficient bifunctional materials is crucial for self-powered flexible systems. Few-layer 1T-MoS2, featuring a layered structure and abundant active sites, is an ideal candidate for supercapacitors and the hydrogen evolution reaction (HER). However, conventional synthesis methods provide limited control over active site exposure. Here, we anchor few-layer 1T-MoS2 nanosheets onto carbon cloth and subsequently apply plasma treatment. This treatment uniformly introduces active sites, facilitates the 2H to 1T phase transition, and enhances the specific surface area. As a result, the optimized MoS2-100 (plasma treatment at 100 W) electrode delivers a high areal capacitance of 646.6 mF cm-2 at 1 mA cm-2. A symmetric supercapacitor assembled with MoS2-100 achieves an energy density of 135.6 μWh cm-2 at 800 μW cm-2 and retains 92.7% of its initial capacitance after 4,000 cycles. Moreover, the electrode exhibits excellent HER activity in acidic medium, with a low overpotential of 289 mV at ~10 mA cm-2 and a Tafel slope of 90.7 mV dec-1. Linear fitting results further reveal that MoS2-100 achieves a Cdl value of 59.9 mF cm-2, approximately twice that of MoS2-0 (untreated). In summary, this work presents a simple and scalable strategy for fabricating few-layer MoS2-based self-supported electrodes with increased active site density, enabling bifunctional capabilities for flexible energy storage and electrocatalysis.