Increasing efficiency and lifetime of electrode packages through plating

ZSW, Etogas and the Holzapfel Group jointly develop a manufacturing concept for producing hydrogen by electrolysis 

The generation and use of renewable energy, e.g. hydrogen (H2) as an energy carrier, is currently a crucial and recurring topic across all industries. The same applies to plating technology. The principal aim here is to provide components intended for use in renewable energy plants with additional or improved properties by means of surface finishing technology. For example, with anti-corrosion coatings that make components more durable and thus lengthen their life cycles or increase the efficiency of generation systems.

Since 2012, the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW), ETOGAS GmbH as developer and manufacturer of turnkey power-to-gas and power-to-hydrogen plants, and the surface finishing specialist Holzapfel Group have been working on a joint project to optimise a hydrogen production plant in the 300-kW class, which will later also enable upscales into the megawatt range.

Plating increases efficiency and longevity

With regard to plating, the focus is on increasing electrical efficiency and long-term stability and improving corrosion protection. As a surface finishing specialist, the Holzapfel Group was invited to join the project to handle these subtasks. Holzapfel's contribution to the project was to improve the platings on parts that play a major role in the inner workings of the hydrogen production plant, i.e. the electrode packages that generate hydrogen and oxygen, which are used for alkaline water electrolysis (AEL). These electrode packages consist of an anode, a cathode and a centre plate, which are firmly bonded with one another. The system contains an electrolyte (caustic potash and water mixture). Its water content is split by introducing an electric current, forming hydrogen at the cathode and oxygen at the anode. The centre plate acts as a separator between the gas spaces. The Holzapfel Group used a specially developed nickel-based process to plate the anode, cathode and centre plate components. In order to boost efficiency and counteract degradation, the cathode was treated with an additional plating. This combination optimised both the catalytic properties and the level of efficiency in the system as a whole.

Enabling industrial production of the electrode packages

"When developing the electrode platings and the firm bonding between the electrode packages, we did not only focus on corrosion protection and increasing electrical efficiency," explains Michael Kolb, head of the Holzapfel Group's innovation team and responsible for the project. "It was also a matter of developing manufacturing concepts that enable electrode packages to be cost-efficiently produced under industrial conditions, including series production. With the process steps taken to date, we are well on the way to developing marketable electrode packages." Furthermore, the development was designed in such a way that the electrode packages can be specifically adapted to the requirements of customers and their systems. For example, the distances between the anode, the cathode and the centre plate can be variably adjusted to meet customer requirements with respect to the gas spaces. The distance between the anode, the cathode and the diaphragm can also be adapted to suit the respective technical conditions. The aims of the project include the market-ready development of core components and subsystems for manufacturing hydrogen generation plants.

In collaboration with project partners, the electrolysis was first tested on a smaller scale using various sizes and platings. At present, a complete electrolyser with the current state of the electrode packages is being installed and tested within the overall concept of the P2G project.

Hydrogen has many uses

 

The electrode packages serve to produce hydrogen. The hydrogen extracted using this method has a great many direct applications, for example in medical technology. In this project, the hydrogen is stored in the form of gas for later use. For example, it can be fed into the natural gas grid (power-to-gas plants; methane production), combined with conversion into electricity or heat by means of gas turbines, used to power combustion engines, or in fuel cells at a later point in time (long-term storage). The hydrogen produced can also be used in a host of other applications, such as fuel for powering fuel cell vehicles, or in the food industry for producing fats.

The renewable production of hydrogen (H2) is gaining importance worldwide. Hydrogen provides a sustainable, resource-efficient supply of energy. It is largely based on renewable energy and is certain to become fully self-sufficient in years to come.

Functional principle of a single alkaline electrolysis cell
Source: ZSW

Power-to-gas: Process diagram and integration in the energy system