Layered MXene-transition metal oxide nanocomposite revealing its versatility in methanol oxidation and PVA/KOH hydrogel-based symmetric supercapacitor

Abstract

To find a solution to the global energy demand, efficient energy production and storage devices are utmost required. Taking advantage of the unique combination of hydrophilicity and conductivity of MXene, a bifunctional nonnoble metal-based electrode NiCo2O4/NiO/MXene (CNOT) is developed. Low conductivity and aggregation of transition metal oxides are compensated by making a hybrid of NiCo2O4/NiO with MXene. CNOT, as an anode catalyst in direct methanol fuel cell (DMFC), offers methanol oxidation reaction current density of 15 A/g and low onset potential. Symmetric supercapacitor developed using CNOT in 3 M KOH solution offers 0.9 V potential window, and 32.66 Fg − 1 specific capacitance at 2.5 A/g. Whereas, symmetric supercapacitor CNOT//CNOT in PVA/KOH hydrogel polymer electrolyte provides a broader window of 1.4 V, with specific capacitance of 87.331 Fg − 1 , and very high energy and power density of 23.77 Wh/kg and 1808.87 W/kg, respectively, at 2.5 A/g. The hydrogel polymer electrolyte (PVA/KOH) outperforms aqueous 3 M KOH by providing a larger window, higher capacitance, excellent energy and power density. Thus, the hybrid electrode provides synergistic effects of the electro-active NiCo2O4, NiO and MXene nanosheets and exhibits versatility in DMFC and symmetric supercapacitor.