Utilization of waste tea leaves as metal-free catalyst for hydrogen generation via ethanolysis of Sodium Borohydride

Abstract

In the present study, waste green and black tea leaves have been used to synthesize metal–free catalysts for hydrogen generation by ethanolysis of sodium borohydride by the acetic acid activation and carbonization. The FTIR, BET, SEM-EDS, and XPS characterizations have been performed to analyze the synthesized catalysts' properties. The parameters such as amounts of catalysts, SB, and reaction temperature were studied while performing the experiments. They were optimized using the Response Surface Methodology (RSM) to obtain the highest values of Hydrogen Generation Rates (HGR) of 1350 ml min−1 g catalyst−1 and 2700 ml min−1 g catalyst−1 using the acetic acid activated black tea (AA – BT) and acetic acid activated green tea (AA – GT) catalysts respectively with the activation energies of 13.14 kJ mol−1 and 37 kJ mol−1. The BET analysis has revealed that the AA – GT and AA – BT catalysts have surface areas of 22.96 m2 g−1 and 3.28 m2 g−1, pore diameters of 1.72 nm and 1.70 nm and pore volumes of 0.0047 and 0.0331785 m3 g−1 respectively. The electrochemical analysis has revealed that the synthesized metal–free catalysts AA – BT and AA - GT possess good specific capacitances of 63.77 mF cm−2 and 121 mF cm−2, which shows that both can be used as electrode material for energy storage applications. Hence, it can be believed that both metal–free catalysts can act as dual functional materials, which can act as catalysts and energy storage materials.