Black and green: catalyst and membranes for fuel cells

The global energy landscape is changing rapidly and the demand for smart, environmentally friendly and cost effective energy solutions is growing. Fuel cells represent the green alternative to the battery world. They stand out due to their high efficiencies of up to 60 % and reach increasing importance in stationary applications but also in the transportation sector. In this application report we will discuss the role of particle size, zeta potential and surface zeta potential in the development and quality control of catalyst and ion exchange membranes for fuel cells.

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel such as hydrogen, and an oxidizing agent, such as oxygen, into electricity by electrochemical reactions (1).
In batteries the chemical energy usually emerges from their limited amounts of metals, metal ions or oxides (1). In contrast to conventional batteries, fuel cells require hydrogen and oxygen to sustain the redox reaction and are therefore able to supply electrical energy over much longer time periods. For this reason fuel cells have been used for decades in space technologies and stationary fuel cells have been installed in utility power plants, hospitals, hotels, or office buildings. For the near future fuel cells represent also the new power source for the transportation sector.
The highest benefit over conventional combustion-based technologies is the high efficiency of up to 60 % (described as the ratio between the electricity produced and hydrogen consumed) as well as their climate friendliness (1). If pure hydrogen is used as a fuel, only heat and water are emitted as byproduct. Therefore fuel cells are considered to be smart, clean and efficient components to generate energy.
Although there are many types of fuel cells (as shown in Table 1) the basic components are very common: an anode, a cathode, and an electrolyte that allows ions to move between the two electrodes of the fuel cell. At the anode a catalyst causes the supplied fuel to undergo oxidation reactions that generate ions (H+) and electrons. The H+ moves from the anode to the cathode through the electrolyte, which can be a liquid or a solid. At the same time, the generated electrons flow from the anode to the cathode through an external circuit, directly producing electricity.

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