A theoretical and experimental investigation of proton transport between the electrolyte in a reversible fuel cell and a carbon-based hydrogen storage
Creators: name: Heidari, Shahin
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401703
subject: Energy generation, conversion and storage (excl. chemical and electrical)

description: The present research work investigates experimentally the reversible electrochemical hydrogen storage capacity of activated carbon (aC) made from different precursors. In addition, the feasibility of running a proton flow battery with an integrated solid activated carbon sample electrode is reported.<br><br>Considering the outcomes of the literature review and the results of previous research work on electrochemical hydrogen storage at the RMIT University (including hydrogen storage in metal hydride and activated carbon with solid electrolyte), the hydrogen storage capacities of activated carbon elelectrodes with a liquid acidic electrolyte have been studied in this thesis. In total thirteen activated carbon samples were investigated in the present research work: one made from charcoal , five from Victorian brown coal, and seven fromphenolic resin were. The solid electrodes from these aC samples were fabricated and then tested to determine their proton conductivity, electron conductivity, double layer capacitance, and reversible electrochemical hydrogen storage capacity. Finally, a candidate aC sample from all the tested electrodes was selected and employed in an experimental proton flow battery to test its feasible running.<br><br>The proton conductivity of the sample activated carbon electrodes was found to be in the range of 0.004 – 0.09 S/cm. The proton conductivity of the sample electrodes increased with increase in average pore volume because with high pore volume the electrode could accommodate more sulphuric acid leading to enhancement in proton conductivity. The double layer capacitance of the sample activated carbon electrodes was found to be in the range of 28.3 – 189.4 F/g. This capacitance contributed to the equivalent mass% of hydrogen storage in the carbon electrode. This capacitance contribution was found to be in the range of 0.03 – 0.19 mass%.<br><br>The total reversible electrochemical hydrogen storage capacities of the fabricated aC-PTFE electrodes immersed in 1 mol. dilute sulphuric acid were found to be in the range of 0.36 – 1.6 mass% of equivalent hydrogen in carbon, counting boththe contributions from chemical reactions between hydrogen and the storage material (i.e. carbon) and the double-layer capacitance effect.<br><br>A candidate aC sample (mesoporous carbon 1:7 KOH) from all the tested electrodes was selected to be employed in an experimental proton flow battery to test its feasible running. The candidate aC was selected based upon its optimum performance in proton conductivity, double layer capacitance and electrochemical hydrogen storage capacity.<br><br>The experiments in the specially designed and fabricated proton flow battery resulted in the feasible running of the device with an integrated solid carbon-based hydrogen storage electrode. It was shown successfully that hydrogen could go in and out from the activated carbon electrode soaked in dilute sulphuric acid. The URFCs with the aC electrode was charged at constant current and constant voltage for nine consecutive cycles to study its performance. The highest discharge value was found to be 1.09 mass% of hydrogen storage, which is comparable to the commercially available metal-hydride based hydrogen cylinders, lithium-ion batteries and lithium-polymer batteries.