Hydrogen generation by electrolysis under subcritical water condition and the effect of aluminium anode

The productions of catalytic active materials and the reactor designs increasing the kinetics of the system are very important because of efficient energy production for electrolysis systems. In this study, the effects of subcritical water's conditions on electrolysis were investigated. All experiments were carried out under the subcritical water conditions, high temperature and pressure resistant reactor was used and the three electrodes were integrated in to the reactor. The aluminium anode was used to prevent the formation of oxygen in the reactor during obtaining pure hydrogen gas. The effect of pure (Al), Al-6013 and Al-7075 aluminium anodes on the electrolysis of water were investigated and compared with Pt anode. For all electrodes, Pt was used as cathode and Ag/AgCl electrode was used as reference electrode. Electrochemical Impedance Spectroscopy (EIS) measurements, current potential measurements were managed at -2 V, electrolysis current at 2 V constant potential during 1800 s was being followed and gas volume produced was measured to determine the most efficient aluminium anode. Energy consumption and hydrogen gases efficiency were also calculated for 25 degrees C room temperature. After determining the most efficient aluminium anode, the experiments were repeated in the subcritical water environment. Nitrogen gas was used to purge the system. The temperature was 130 degrees C and the pressure was 20 Bar. As a result, the use of aluminium alloys as an anode under the subcritical water conditions reduced energy consumption from 1400 kJ mol(-1) to 300 kJ mol(-1). The current density was increased to 370 mA cm(-2) at 2 V. The efficiency increase from %15 to %70, and the amount of hydrogen gas produced was increase from 18 mL cm(-2) h(-) to 300 mL cm(-2) h(-). In addition, using the aluminium anode eliminated the gas separation processes by providing purer hydrogen gas production. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.