A new concept for a particulate trap for diesel engines has been developed. The trap is a combination of a ceramic wall-flow filter and an electrochemical reactor. When trapped in the filter, the soot particles are continuously converted to carbon dioxide by an electrochemical reaction. This reaction is activated by applying a small voltage to an electrochemical reactor, consisting of the walls of the filter element. The filter element is constructed as an electrochemical reactor with a ceramic, oxygen ion conducting electrolyte and ceramic or metallic electrodes which are both electronic conducting and catalytically active. By controlling the processing parameters of the materials, the porosity of the filter can be adjusted thus allowing the majority of the soot particles to penetrate into the filter unit and be collected at the electrode/electrolyte interface. Here the soot will be electrochemically converted to carbon dioxide, even at relatively low temperatures. The lower temperature threshold is approximately 250°C and is limited by the need for a sufficient electrical conductivity in the electrolyte material in order to obtain an acceptable rate of reaction.
