MoWS2 nanosheets incorporated nanocarbons for high-energy-density pseudocapacitive negatrode material and hydrogen evolution reaction

Abstract

The rapid population explosion and widespread use of non-renewable energy sources have led to preoccupations such as the energy crisis, which motivates us to find alternative energy supplies and further harness their output energy through energy storage devices. In this work, we have demonstrated hybrids incorporating MoWS₂ and nanocarbon (MWCNT and rGO) as bifunctional materials, i.e., electrocatalyst and negatrode (negative electrode), for both energy conversion and storage applications. All the fabricated electrodes underwent various characterization techniques including pXRD, Raman spectroscopy, FESEM, HRTEM, XPS, and BET, and were later subjected to electrochemical and electrocatalytic measurements. The MoWS₂ incorporating MWCNTs outperformed all the prepared materials, attaining a highest capacitance of 592 F g⁻¹ at a current density of 0.2 A g⁻¹. An asymmetric device was also fabricated using CoSe₂@CNT@rGO as the positive electrode and MoWS₂@MWCNT as the negative electrode, and it achieved a highest capacitance of 151 F g⁻¹ with an energy density of 36 W h kg⁻¹, corresponding to a power density of 14 kW kg⁻¹, and exceptional capacitance retention and coulombic efficiency of 96% and 97%, respectively. The pseudocapacitive negatrode materials were demonstrated to be applicable for electrocatalytic HER applications with decent performance (η₀: 175 mV, Tafel slope: 34 mV dec⁻¹) and outstanding sustained stability of up to 12 hours. The higher surface area, barrier-free pathway for charge transfer, role of the valence electrons in the metal ions, rapid charge kinetics, and highly suitable active sites contributed significantly to the better electrochemical and electrocatalytic activity of MoWS₂@MWCNT. First-principles DFT calculations were also executed to validate the supercapacitive performance by means of quantum capacitance.