Experimental and theoretical study of MoSi₂ and WSi₂ electrodes for high-performance supercapacitors

Transition metal silicides display a distinctive blend of metallic and ceramic characteristics, characterized by outstanding electrical conductivity, high-temperature durability, and exceptional cycling stability. To fully harness these properties, achieving an ultrafine structure, pure phase, and large specific surface area is crucial, enhancing their electrocatalytic performance. This study successfully synthesized WSi₂ and MoSi₂ particles through a one-step solid-state diffusion (SSD) process. The formation mechanisms of the MoSi₂ and WSi₂ particles were investigated by varying the temperature during the annealing process. The MoSi₂ electrode demonstrated exceptional capacitance (404 F g⁻¹ at 2 A g⁻¹) and outstanding cycle stability (retaining 94 % of its initial performance after 5000 cycles). Additionally, the assembled asymmetric supercapacitor using MoSi₂//AC prototype exhibited a high energy density of 46.6 Wh kg⁻¹ at 4.8 kW kg⁻¹ power density. Density functional theory estimation confirmed the metallic nature of XSi₂ (X = W, Mo) and contributed to enhancing the density of states and energy level accumulation for efficient supercapacitors. The observed results attributed the active edges and porous nature promote the electrolyte diffusion during charge storage kinetics in the metal silicide electrodes.