Acceleration of hydrogen production using microalgae-based activated carbon and development of a prototype supercapacitor with enhanced performance under corona effect

In this study, Dunaliella Salina microalgae was used as a bifunctional material both as a supercapacitor electrode material and as a catalyst material for hydrogen production. Parameters such as type of chemical activation material, amount of activation material, burning temperature and burning time were determined for chemical activation/carbonization for activated carbon production and Taguchi orthogonal arrays method L9 (3,4) was used as an alternative to classical methods for experimental design. The activated carbons obtained by the determined experimental design were used as supercapacitor electrode materials and their electrochemical performances were investigated. The best specific capacitance value was obtained for the MAD-3 electrode with 284.86 F/g at 1 A/g current density. By applying a linear regression model to the obtained specific capacitance values, it was observed that the most significant effect on the specific capacitance value among the experimental parameters was the combustion temperature parameter. The MAD-3 electrode material was then subjected to corona discharges at different application voltage frequency values to improve its electrochemical performance. The capacities of all electrodes obtained by electrical activation were higher than the MAD-3 electrode, and the best capacitance value was obtained for the MAD-C50 electrode at the lowest frequency value of 50 Hz application voltage frequency with a value of 335.23 F/g at a current density of 1 A/g. The results of SEM and BET analysis of the material showed that corona discharge increases the surface area and pore volume of activated carbon and thus improves the electrochemical performance of supercapacitor electrodes. The capacitance reduction for MAD-C50 after 1000 cycles at 2 A/g current density was calculated as 15% and 22.57% for 2000 A/g at 10 A/g current density. However, the energy density of MAD-C50 was calculated as 19.92 Wˑh/kg at a power density of 485.50 W/kg. In addition, the obtained activated carbons were used as catalysts in the methanolysis of NaBH4 and the highest HU(max) value was measured at 60 °C ambient temperature with 13.085 mLˑmin-1gcat-1 in the presence of 0.1 g catalyst and 0.25 g NaBH4. According to the linear regression results, the H3PO4 parameter showed the most significant effect on the maximum hydrogen production rate. The results showed that Dunaliella Salina microalgae exhibited a good performance in terms of both electrochemical and hydrogen production.