Overcoming Instability Challenges of Binder-Free, Self-Standing 1T-TiS2 Electrodes in Aqueous Symmetric Supercapacitors Through Dopamine Functionalization

Two-dimensional materials draw considerable interest for energy storage. Semimetallic phases of transition metal dichalcogenides (TMDs), notably titanium disulfide (TiS2), are extensively studied for their distinctive electronic, chemical, and optical traits. TiS2, initially proposed for Li-ion batteries, holds promise for supercapacitors, although its utilization faces stability challenges in aqueous environments. Herein, electrically conducting and surface-passivated 2D 1T-TiS2 flakes were fabricated and tailored for application as electrodes in supercapacitors with enhanced durability. For this purpose, self-standing and flexible 1T-TiS2 films were fabricated using vacuum filtration and treated with dopamine (DA) to obtain electrochemically stable supercapacitor electrodes in aqueous environments. During DA treatment, in-situ generation of hydrogen peroxide (H2O2) leads to the formation of a thin titanium oxide (TiO2) overlayer on TiS2, enhancing oxidation stability. At a scan rate of 10 mV s-1, a single electrode demonstrated a gravimetric specific capacitance of 128 F g-1, a volumetric specific capacitance of 122 F cm-3, and an areal specific capacitance of 244 mF cm-2. The symmetric supercapacitor device demonstrated an impressive capacity retention of 96.1% after 10000 cycles and 85.5% after 18000 cycles. These results pave the way for utilizing 2D 1T-TiS2 in aqueous environments, expanding its possible applications and holding promise for significant advancements in the field. Electrically conductive 2D nanosheets of 1T- TiS2 are fabricated. These nanosheets have been treated with dopamine to enhance their stability in aqueous environments through surface passivation. The addition of thiourea to the electrolyte has resulted in a significant enhancement in the cyclic stability of TiS2 electrodes up to 10000 cycles. This advancement has led to the development of stable 1T-TiS2 based aqueous symmetric supercapacitors. [Display omitted] •Oxidation-resistant, binder-free, self-standing 1T-TiS2 electrodes with high electrical conductivity were fabricated and used in symmetric supercapacitor devices.•The aqueous stability of 2D 1T-TiS2 electrodes was significantly improved via dopamine treatment through the formation of a thin TiO2 overlayer functionalized by dopamine.•A maximum Coulombic efficiency of 99% from fabricated devices and a capacity retention of 96.1% were obtained after 10000 cycles