Boosting the Multifunctional Properties of MnCo2O4-MnCo2S4 Heterostructure for Portable All-Solid-State Symmetric Supercapacitor, Methanol Oxidation and Hydrogen Evolution Reaction

This article reports on the preparation of MnCo2O4-MnCo2S4 heterostructure by facile solvothermal route towards the application of supercapacitor-based energy storage as well as methanol electro-oxidation and hydrogen evolution reaction. Dunn's methodology has been adopted for the evaluation of charge storage by capacitive process and diffusion-controlled process and the quantification of the charge stored at exterior surface and interior surface was done by Trasatti's approach. The prepared heterostructure was utilized as an electrode in the symmetric solid-state device based on Na2MoO4 redox electrolyte and exhibits remarkable performance in terms of specific capacity, cyclic performance, energy, and power density. The fabricated device exhibits a specific capacity of 417 C g(-1) at a specific current of 1 A g(-1), and shows retention of 84.2 % after 5000 galvanostatic charge-discharge cycles, and specific energy of 81 Wh kg(-1) at a specific power of 700 W kg(-1). Series combination of two solid-state symmetric devices was capable to light up a red LED for 30 min and an array of 22 red LEDs for 8 min. The heterostructure shows remarkable catalytic activity for methanol electrooxidation by increasing catalytic current almost four times in 2 M methanol and 1 M KOH electrolyte at 0.6 V and also lowering the onset potential as 0.331 V. The excellent electrocatalytic activity of MnCo2O4-MnCo2S4 heterostructure towards the hydrogen evolution reaction was observed by showing the requirement of low overpotential (-175 mV) to reach the current density of -10 mA cm(-2) along with small Tafel slope (102 mV dec(-1)). The electrode material revealed enormous stability by providing a constant current over 20 h in chronoamperometry measurements. The better electrochemical performance of microspheres could be attributed to large surface area which promotes the catalytic reactions at the large number of active sites.

Automated summary

This study reported the preparation of MnCo2O4-MnCo2S4 heterostructure by solvothermal route for applications in supercapacitor-based energy storage, methanol electro-oxidation, and hydrogen evolution reaction. The prepared heterostructure exhibited remarkable performance in terms of specific capacity, cyclic performance, energy, and power density. Additionally, the fabricated device based on this heterostructure showed excellent catalytic activity for methanol electrooxidation and hydrogen evolution reaction, as well as reliable performance in lighting up LEDs.