In China's ongoing quest to address climate change and facilitate a transition to a green and low-carbon economy, the 3060 target (carbon peak by 2030 and carbon neutrality by 2060) represents a critical strategy. This commitment, integral to China's long-term environmental goals, serves as a cornerstone for global carbon neutrality efforts. A crucial aspect of this strategy is the development and implementation of clean hydrogen production methods, particularly hydrogen production by water electrolysis. As one of the primary methods of producing green hydrogen, water electrolysis plays a pivotal role in achieving the country’s ambitious carbon reduction goals. The efficiency of hydrogen production via electrolysis is significantly influenced by the voltage of the electrolytic cells, which is impacted by a multitude of factors. This article will explore the factors affecting electrolysis cell voltage and the critical role of diaphragm materials in hydrogen production.
Factors Affecting Electrolysis Cells Voltage
1. Membrane Structure
One of the most influential factors in determining the electrolysis cell voltage is the membrane structure used in the electrolysis process. The membrane serves as a barrier between the cathode and anode, separating the hydrogen and oxygen gases produced. Several membrane properties influence the electrolysis process, including material, thickness, porosity, and surface properties. High-quality membranes with low resistance allow for easier ion flow, reducing the electrolysis cell voltage. Membrane materials with better ionic conductivity will facilitate the movement of ions more effectively, leading to lower energy requirements for the electrolysis process.
2. Current Density
Current density, or the amount of electric current passed through a given area of the electrolyte, directly impacts the voltage of the electrolytic cell. As the current density increases, the electrolytic cell voltage typically increases as well. This rise in voltage is attributed to factors like ohmic resistance, polarization resistance, and heat generation within the system. High current densities can lead to significant energy losses due to these resistances, which subsequently require higher voltages to maintain the electrolysis process.
3. Potassium Hydroxide Concentration
The electrolyte used in water electrolysis is often a potassium hydroxide (KOH) solution. The concentration of KOH plays a critical role in determining the conductivity of the electrolyte, which in turn affects the electrolysis cell voltage. A higher concentration of KOH generally results in improved conductivity, which reduces the resistance in the cell and lowers the required voltage. Typically, a KOH concentration of around 30% is maintained in alkaline electrolysis systems. If the concentration is too low, the resistance increases, and the cell voltage must rise to compensate for the lack of ion flow.
4. Spacing Between Electrodes
The distance between the cathode and anode is another important factor that affects the electrolysis cell voltage. A larger spacing between electrodes increases the path length for ion migration, which raises the resistance in the electrolyte and, consequently, the voltage required to drive the electrolysis process. Proper spacing between electrodes ensures uniform distribution of the electric field and minimizes the adverse impact on voltage stability. Inadequate electrode spacing can lead to localized areas of high resistance, resulting in higher voltage demands.
5. Lye Circulation Volume
The circulation of the electrolyte, or lye, around the electrodes is another critical parameter that influences electrolysis cell voltage. Proper circulation ensures that the concentration of ions near the electrode surfaces remains uniform, promoting efficient electrolysis. If the circulation volume is insufficient, the electrolyte may become depleted of ions near the electrodes, leading to an increase in cell voltage. Furthermore, poor circulation can result in the accumulation of reaction products around the electrode surfaces, which impedes the contact between the electrolyte and electrodes, raising the required voltage.
6. Temperature
Temperature plays a significant role in electrolysis cell voltage. As temperature increases, the viscosity of the electrolyte decreases, allowing ions to move more freely and enhancing the electrical conductivity of the electrolyte. This, in turn, lowers the resistance in the system and reduces the required voltage. However, excessively high temperatures can lead to unwanted side effects such as accelerated membrane degradation, gas evolution inefficiencies, and system instability. Therefore, maintaining an optimal temperature range is essential to ensure efficient electrolysis while preventing damage to the system.
7. Impurities in the Lye
The presence of impurities in the electrolyte can alter the ionic conductivity of the solution and affect the electrolysis cell voltage. Impurities can participate in side reactions at the electrodes or even contaminate the membrane, resulting in reduced efficiency and increased voltage. Common impurities in lye include metal ions, organic compounds, and contaminants from the electrode or membrane materials. These impurities can interfere with the intended electrochemical reactions and increase the resistance of the electrolyte, requiring higher voltage to maintain the process.
8. Electrode Active Coatings
Electrode coatings, particularly those that include precious metals like platinum or iridium, play a critical role in reducing the voltage required for the electrochemical reactions. These coatings enhance the activation of the electrodes, allowing the reactions to proceed more efficiently. By improving the catalytic activity at the electrodes, active coatings reduce the overpotential, which is the extra voltage required to drive a reaction. The use of high-quality electrode coatings can significantly decrease the electrolysis cell voltage and improve overall system efficiency.
9. The Number of Starts and Stops
The start-up and shutdown processes in an electrolysis system also affect the performance of the electrolytic cell over time. Each start-up and shutdown introduces a certain amount of polarization on the electrode surfaces, which gradually accumulates with repeated cycles. This polarization leads to an increase in the overpotential required for electrolysis, which in turn raises the overall voltage of the system. Frequent starts and stops can also affect the stability of the membrane, further impacting the electrolysis efficiency.
The Role of Diaphragm Materials in Hydrogen Production by Water Electrolysis
As water electrolysis becomes an increasingly popular method for hydrogen production, the diaphragm, or membrane, plays a critical role in ensuring the efficiency and safety of the process. The diaphragm acts as a physical barrier that separates the hydrogen and oxygen produced at the cathode and anode, respectively. In addition to its separation function, the diaphragm facilitates the movement of ions within the electrolyte, thereby enabling the electrochemical reactions necessary for hydrogen production.
1. Ion Transport
Diaphragms allow for the selective transfer of ions, such as hydroxide ions in alkaline electrolysis systems. This ion transport is essential for maintaining the continuity of the electrolysis process. The diaphragm must be permeable enough to allow the passage of ions but impermeable to gases such as hydrogen and oxygen, which must be kept separate to prevent recombination.
2. Safety Barrier for Gases
One of the primary functions of the diaphragm is to prevent the crossover or permeation of gases between the electrodes. If hydrogen and oxygen mix, they can form an explosive mixture, posing a significant safety risk. Therefore, the diaphragm acts as a safety barrier, ensuring that the gases produced at the cathode and anode remain isolated.
3. Electrical Insulation
The diaphragm also serves as an electrical insulator, preventing the transfer of electrons between the electrodes. This ensures that the electrolysis process proceeds in a controlled manner, with the flow of current confined to the electrolyte solution. The diaphragm thus helps maintain the efficiency of the electrolysis process by ensuring that the current flows only through the intended ionic pathways.
The Role of BoLian in the Hydrogen Industry
BoLian, a company at the forefront of filter cloth and membrane material technologies, has recognized the growing importance of hydrogen production in the context of global efforts to reduce carbon emissions. Hydrogen is increasingly seen as a cornerstone of the transition to a low-carbon economy, offering clean, sustainable energy solutions for a range of industries. With its deep expertise in materials science, BoLian has embraced the role of innovating membrane materials for water electrolysis, a method widely regarded as one of the most efficient and sustainable ways to produce green hydrogen. These innovative membranes are essential for improving the efficiency and performance of water electrolysis systems, ensuring that hydrogen production processes can meet the demands of global decarbonization goals.
In 2024, BoLian further strengthened its position by announcing a strategic collaboration with Dalian Polytechnic University. This partnership is focused on the development of composite membrane materials tailored specifically for hydrogen production. The goal is to upgrade existing diaphragm materials, improving their performance in terms of ion conductivity, mechanical strength, and chemical resistance. BoLian’s cutting-edge research has led to the development of new composite membranes that not only demonstrate superior efficiency but also offer enhanced scalability, an essential attribute for large-scale hydrogen production. These advancements are expected to play a critical role in reducing the overall cost of green hydrogen, making it more competitive with traditional fossil fuel-based energy sources.
Conclusion
Hydrogen production via water electrolysis is poised to play a significant role in global efforts to achieve carbon neutrality. As the demand for clean energy grows, the efficiency of electrolysis systems will be critical in ensuring that hydrogen remains a viable alternative to fossil fuels. The efficiency of this process is heavily dependent on factors such as membrane structure, current density, electrolyte concentration, electrode spacing, and temperature. Diaphragm materials, in particular, are crucial for ensuring the safety, efficiency, and longevity of electrolysis systems by providing essential functions like gas separation, ion transport, and electrical insulation. Innovations in these materials will be essential for optimizing electrolysis performance and enabling the widespread adoption of hydrogen as a clean energy source.
As the hydrogen industry continues to grow, advancements in membrane technologies, such as those developed by BoLian, will be key to improving electrolysis cell performance. These innovations will help reduce the energy consumption of hydrogen production and enhance the scalability of systems, accelerating the adoption of green hydrogen as a key component of a low-carbon energy future. With its ongoing research and strategic partnerships, BoLian is set to remain at the forefront of this exciting and rapidly evolving field, contributing to the global drive toward sustainable energy solutions.
