A Novel Tea factory waste metal-free catalyst as promising supercapacitor electrode for hydrogen production and energy storage: A dual functional material

Abstract

In this study, the catalyst produced from tea factory waste (TFW) was used for the first time for hydrogen production by methanolysis of sodium borohydride (NaBH4). The produced material had a dual function as both catalyst and supercapacitor; therefore, it was named ‘cap-cat’(capacitor-catalyst) by us. In this context, TFW was treated with acetic acid for 24 h at 80 °C. The sample was then subjected to combustion in the oven to synthesize the catalyst. Afterward, the most efficient TFW-CH3COOH catalyst was synthesized by evaluating different acid ratios, burning temperatures and times. The best conditions for the acetic acid ratio, burning temperature, and time were found out 3 M, 300 °C, and 60 min. The characterization of the catalyst was done using SEM-EDX, FTIR, XRD analysis. Hydrogen generation experiments from NaBH4 by methanolysis were performed at various catalyst concentrations in the range of 0.05–0.2 g, diverse NaBH4 ratio of 1 to 7.5%, and at different reaction temperatures (30–60 °C). The HGR of the synthesized catalyst was recorded as 3096.4, 8367.5, 11227.9, and 23,507 mLmin-1gcat-1 for these temperatures (30, 40, 50, and 60 °C), respectively. Also the activation energy was calculated as 38.6 kJ mol−1. Subsequently, the CV (cyclic voltammetry) and charge–discharge curves of the prototypes produced were substantially similar to the supercapacitor curves in the literature. Gravimetric capacitance was found to be 155F/g at a current density of 2 A/g.