Biomass-based metal-free catalyst as a promising supercapacitor electrode for energy storage

In present study, biomass doped H 3 PO 4 -Cat, named as STW-H 3 PO 4 -Cat, was used as a catalyst in the methanolysis of sodium borohydride (NaBH 4 ). Spent tea waste (STW) was used for the first time in this study as biomass. The generated existing catalyst was also employed as an active supercapacitor material, demonstrating its dual function. To identify the most active catalyst in the methanolysis of sodium borohydride, the catalyst was functionalized in different H 3 PO 4 concentrations (1–7 M), and different annealing temperatures (200–500 °C) and different annealing times (20–80 min). Optimum parameters were determined as 7 M H 3 PO 4 , 400 °C, and 40 min. The maximum hydrogen production (HPR) value and the activation energy ( E a ) were determined as 76,640 mL min −1 g cat −1 and 12.03 kJ mol −1 . When the catalyst was investigated in terms of the supercapacitor, the electrode's capacitance at 1 A/g current intensity was found to be 158 F/g utilizing the charge–discharge curve. The catalyst with optimum conditions was structurally and morphologically characterized by Fourier Transform Infrared (FTIR), x-ray diffraction (XRD), and scanning electron microscope (SEM) measurements, respectively.