Despite a sustained decline in pollutant emissions in Europe in recent decades, legal limits are still being exceeded, particularly in urban areas where around 90% of European city dwellers are exposed to dangerous levels of particulate matter. This exposure leads to serious respiratory diseases, lung cancer, strokes and premature mortality and shortens life expectancy in the EU by more than eight months. The average city dweller spends 90% of their life indoors, where hazards arise from emissions from building materials, furniture, textiles, mould spores and daily activities such as cooking and heating. Energy-efficient buildings exacerbate the problem as they reduce natural air exchange to minimise heat loss. Therefore, the demand for efficient and less energy-intensive methods of air treatment is growing.

One way to optimise the energy efficiency of air filtration is to use an electric ioniser to charge the particles. This charging has the great advantage that electrically charged particles improve the separation efficiency of downstream mechanical filters (electret filters) or electrical filters (electrostatic precipitators). In this way, significantly lower pressure losses and therefore energy-efficient filter systems can be realised. However, until now such electrostatically enhanced filter systems can only be used to a limited extent due to the power-dependent ozone emission and the long-term decreasing stability of the corona discharge (due to wear and contamination of the high-voltage electrodes). The wear behaviour of the electrode is the result of a complex combination of physical and plasma-chemical phenomena. These phenomena include oxidation reactions of the atomic oxygen and the emitted ozone with the electrode surface as well as ion- and electron-induced sputtering, in which high-energy particles collide with the electrode surface. These wear phenomena are also superimposed by deposits and soiling on the electrode. During prolonged operation, these effects can significantly change the electrode geometry and therefore...