TY - BOOK

T1 - Reference electrodes in proton exchange membrane water electrolysis characterization

T2 - experimental investigation of oxygen and hydrogen evolution reaction kinetics

AU - Bühre, Lena Viviane

PY - 2024/7/18

Y1 - 2024/7/18

N2 - Producing clean hydrogen through water electrolysis powered by renewable energy presents an opportunity to reduce carbon emissions across various industries. Additionally, it helps to integrate fluctuating renewables into the energy mix. However, the large-scale production of green hydrogen faces significant challenges, mainly due to high initial investments. To address this challenge, this dissertation focuses on reducing the cost of hydrogen production by improving the characterization of catalyst layers in proton exchange membrane (PEM) water electrolyzers. Characterizing catalyst layers is essential, as their improved kinetic efficiency and durability will help reduce the costs associated with expensive and scarce catalyst materials. Current state-of-the-art characterization methods are limited in providing realistic insights into catalyst layer performance at the full cell level. To bridge this gap, the dissertation investigates the application of reference electrodes as an advanced characterization tool for PEM water electrolysis. Reference electrodes offer insight into the system by enabling the measurement of ionic potential within the cell. This measurement allows for the individual investigation of the catalyst layer performance at each electrode and helps to detect degradation phenomena. The experimental studies conducted in this dissertation demonstrate the integration of two specific reference electrodes, namely a salt bridge reference electrode and a reversible hydrogen electrode, into a standardized test cell. Both setups present unique challenges, such as ensuring regular cell operation. Ultimately, these efforts lead to the design of versatile characterization tools capable of investigating the various loss contributions in PEM water electrolysis. The first application of the setups is the separate characterization of oxygen and hydrogen evolution reaction kinetics. Kinetic parameters, including Tafel slopes and exchange current densities, are determined for both reactions. Continuing with the application of the setups, the relationship between temperature and exchange current density is explored to calculate the activation energies for oxygen and hydrogen evolution reactions. This analysis provides valuable metrics for catalyst development and modeling purposes. As the concluding application, an accelerated stress test is performed. It reveals an increase in activation overpotential over time. The observed degradation can be traced back to changes in the cathodic catalyst layer.

AB - Producing clean hydrogen through water electrolysis powered by renewable energy presents an opportunity to reduce carbon emissions across various industries. Additionally, it helps to integrate fluctuating renewables into the energy mix. However, the large-scale production of green hydrogen faces significant challenges, mainly due to high initial investments. To address this challenge, this dissertation focuses on reducing the cost of hydrogen production by improving the characterization of catalyst layers in proton exchange membrane (PEM) water electrolyzers. Characterizing catalyst layers is essential, as their improved kinetic efficiency and durability will help reduce the costs associated with expensive and scarce catalyst materials. Current state-of-the-art characterization methods are limited in providing realistic insights into catalyst layer performance at the full cell level. To bridge this gap, the dissertation investigates the application of reference electrodes as an advanced characterization tool for PEM water electrolysis. Reference electrodes offer insight into the system by enabling the measurement of ionic potential within the cell. This measurement allows for the individual investigation of the catalyst layer performance at each electrode and helps to detect degradation phenomena. The experimental studies conducted in this dissertation demonstrate the integration of two specific reference electrodes, namely a salt bridge reference electrode and a reversible hydrogen electrode, into a standardized test cell. Both setups present unique challenges, such as ensuring regular cell operation. Ultimately, these efforts lead to the design of versatile characterization tools capable of investigating the various loss contributions in PEM water electrolysis. The first application of the setups is the separate characterization of oxygen and hydrogen evolution reaction kinetics. Kinetic parameters, including Tafel slopes and exchange current densities, are determined for both reactions. Continuing with the application of the setups, the relationship between temperature and exchange current density is explored to calculate the activation energies for oxygen and hydrogen evolution reactions. This analysis provides valuable metrics for catalyst development and modeling purposes. As the concluding application, an accelerated stress test is performed. It reveals an increase in activation overpotential over time. The observed degradation can be traced back to changes in the cathodic catalyst layer.

U2 - 10.15488/17804

DO - 10.15488/17804

M3 - Doctoral thesis

CY - Hannover

ER -