Investigation of hydrogen production and energy storage capacities of catalysts supported by Dağdağan seeds (Celtis australis)

The objective of this study was to investigate the potential of using low-cost, microwave-assisted activated carbon produced from organic waste, specifically dagdagan seeds (DAN), as an efficient catalyst for the methanolysis reaction of NaBH4 and as a high-performance electrode material for supercapacitors. In this context, various parameters were optimized for the synthesis of activated carbon, including the type of chemical activator (KOH, H2SO4, H3PO4, K2CO3, CH3COOH), impregnation ratio (1:0,025, 1:0,05, 1:1, 1:2, 1:3), impregnation time (12s, 24s, 36s, 48s), microwave power (250W, 500W, 750W, 1000W), and microwave duration (5 min, 10 min, 15 min, 20 min). The optimal catalyst, designated as DAN-S, was synthesized using H2SO4 as the chemical activator in a 1:1 ratio, with a 24-hour impregnation time, 500-watt microwave power, and a 10-minute microwave duration. To optimize the effectiveness and performance of the prepared catalyst, various parameters such as reaction temperature, NaBH4 concentration, catalyst amount, and reusability were thoroughly investigated. The maximum hydrogen production rate (HGR) from the 2,5% NaBH4 methanolysis reaction conducted at 30 °C with the DAN-S catalyst was determined to be 8379 mL/min/g-cat. Additionally, the activation energy of this catalyst was calculated to be 42,84 kJ/mol. Characterization of the DAN-S catalyst was performed using SEM-EDX, BET, XRD, and FTIR analysis techniques. Performance tests, including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, were carried out to evaluate the energy storage properties of the most catalytically active catalyst. The results demonstrated that the DAN-S catalyst achieved a capacitance of 73,19 F/g at a current density of 0,25 A/g, an energy density of 2,88 Wh/kg, and a power density of 418,06 W/kg.