A novel dismantlable monolithic-type electrochem. promoted catalytic reactor and "smart" sensor-catalytic reactor unit has been constructed and tested for hydrocarbon oxidn. and NO redn. by C2H4 in presence of O2. In this novel reactor, thin (.apprx.20-40 nm) porous catalyst films made of two different materials are sputter-deposited on opposing surfaces of thin (0.25 mm) parallel solid electrolyte plates supported in the grooves of a ceramic monolithic holder and serve as sensor or electropromoted catalyst elements. Using Rh/YSZ/Pt-type catalyst elements, the 22-plate reactor operated with apparent Faradaic efficiency exceeding 25 achieving near complete fuel and NO conversion at 300 DegC in presence of up to 1.1% O2 in the feed at gas flow rates exceeding 1.3 l/min. The metal catalyst dispersion was of the order of at least 15%. The novel reactor design requires only two external elec. connections and permits easy practical utilization of the electrochem. promotion of catalysis. [on SciFinder (R)]