An electrochemical reactor Au|YSZ|Ag, using yttria-stabilized zirconia (YSZ) as a solid electrolyte, has been employed for the partial oxidation of C-2-C-4 alkanes at 773 K. Catalyst films of Mo-V mixed oxide with various MO/V compositions were prepared by simultaneous deposition of MoO3 and V2O5 on the Au anode of the electro-chemical cell. A stable MoV2O8 mixed oxide formed as the active phase in the catalyst film. When oxygen was pumped onto the catalyst film through the YSZ, ethane and propane were selectively dehydrogenated to ethene and propene, respectively, while isobutane gave a small amount of methacrolein. Preferential orientation of crystal growth Of MoV2O8 was observed depending on the Mo/V composition, resulting in structure-sensitive alkane oxidation. The diffraction lines 001 and 110 of MoV2O8 appeared most strongly for the V content of 43.7 and 53.4%, and the formation of propene and ethene were most efficiently catalyzed on the former and the latter, respectively. The active species is considered to be V atoms on the surface. The (001) plane of MoV2O8 is composed of flat terrace planes, while the (I 1 0) planes consist of many steps, where co-ordinatively unsaturated V atoms appeared more intensively than on the (0 0 1) plane on the surface. It is considered that ethane possessing a primary C-H bond requires more active sites for the C-H activation than propane that possesses a secondary C-H bond. Use of the electrochemical oxygen pumping system onto the MoV2O8 catalyst film caused a drastic enhancement in the oxidative dehydrogenation of ethane and propane compared to use of the conventional gasflow reactor with the fixed-bed, probably due to sufficient supply of dissociated oxygen species through the YSZ. (C) 2004 Elsevier B.V. All rights reserved.