Electrocatalytic Reduction and Selective Absorption of NOx

Solid-state electrochemical cells can be used to sense and reduce NO_x from combustion exhaust gases. In the reduction process the products are N₂ and O₂. For these cells to be effective in fuel-lean combustion exhaust, cathode materials with high selectivity for NO vs. O₂ are necessary. Numerous materials were investigated for NO adsorption and reduction selectivity using temperature programmed desorption and reaction (TPD and TPR), respectively, and a summary of that investigation is given.

Ceramic cells using these materials were fabricated and used to electrocatalytically reduce NO. An enhanced electrocatalytic three-way activity for NO_x reduction was demonstrated that increases the window of operation into fuel-lean conditions. A process that combines selective absorption of NO_x with three-way catalytic or electrocatalytic reduction to further increase the window of operation to higher oxygen concentrations was also demonstrated.