Nitrogen oxides (NO and NO2, called NOx) are major air pollutants released during combustion; easier and more effective NOx treatments offer better protection of human health, and also higher fuel efficiency that will help reduce greenhouse gas emissions. Here, electrochemical double-cell (EDC) plates are shown to exhibit high activities at ambient temperature for promoted decomposition of NOx in oxygen-rich exhaust to nitrogen and oxygen without consuming any reagent or other resource. Metal or anode can be used as the support for the EDC plate, with metal-supported plates being more easily fabricated. EDC plates can almost completely eliminate NOx from combustion exhausts. Very high NO concentrations are preferred, to allow very high combustion temperatures, and so achieve superior fuel efficiency. An optimum cathode loading exists. A module of EDC plates can achieve a similar per area performance to that of a single EDC plate. The reaction mechanism is proposed. (C) 2015 Elsevier Ltd. All rights reserved.