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An effect of Cu powder dispersion and morphology on the surface structure and the physical–chemical and catalytic properties of Cu–CeO₂ catalysts prepared by mechanochemical synthesis was studied in the preferential CO oxidation in a H₂-rich stream (CO-PROX). Two catalysts, produced by 30 min ball-milling from CeO₂ and 8 mass% of copper powders and with particle sizes of several tens (dendrite-like Cu) and 50–200 nm (spherical Cu obtained with levitation-jet method), respectively, were characterized by X-ray diffraction and electron microscopy methods, a temperature-programmed reduction with CO and H₂, and with Fourier-transform infrared spectroscopy. The catalyst synthesized from the “large-scale” dendrite-like Cu powder, whose surface consisted of Cu<i>_x</i>O (Cu⁺) agglomerates located directly on the surface of facetted CeO₂ crystals with a CeO₂(111) and CeO₂(100) crystal planes exposition, was approximately two times less active at 120–160 °C than the catalyst synthesized from the fine Cu powder, whose surface consisted of Cu<i>_x</i>O (Cu²⁺) clusters of 4–6 nm in size located on the steps of facetted CeO₂ nanocrystals. Although a large part of CO₂ reacted with a ceria surface to give carbonate-like species, no blockage of CO-activating centers was observed due to the surface architecture. The surface structure formed by the use of highly dispersed Cu powder is found to be a key factor responsible for the catalytic activity.