New bifunctional carbon material of metal-free pomegranate peel catalyst and supercapacitor for highly efficient hydrogen production and energy storage

Abstract

In this study, pomegranate peel (PP) waste was used as an efficient, cost-effective, and metal-free catalyst for the methanolysis reaction of sodium borohydride (NaBH4); furthermore, the prepared active material was utilized as a supercapacitor for electricity storage. The effect of several parameters, such as different acid concentrations, burning temperature, and burning times on the catalytic performance of the pomegranate peel catalyst (PP-H3PO4-Cat) were examined. Under optimum conditions, the most active catalyst was obtained by burning with 7 M phosphoric acid (H3PO4) solution at 400 degrees C for 45 minutes. The maximum hydrogen generation rate (HGR) obtained from the methanolysis reaction of NaBH4 at 30 degrees C and 60 degrees C was found as 57 200 and 76 228 mL min(-1) gcat(-1), respectively. The activation energy value for the catalytic methanolysis reaction was calculated as 7.89 kJ mol(-1). Furthermore, Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma - optical emission spectrometry (ICP-OES), X-ray diffractometer spectroscopy (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscope (SEM) analyses were performed for characterization of the synthesized catalyst. The gravimetric capacitance of the prepared electrode (catalyst material with best results) was calculated as 29 F/g at 0.25 A/g current density. The electrodes made from biomass waste are both cheap and have a good capacity.