A comparative DFT study of ethanol steam reforming over Co(1 0 0) and CoO(1 0 0) surfaces: Molecular reaction mechanism

• New insights into the roles of Co(0) and Co(II) sites in the Co-catalyzed ethanol steam reforming (ESR) reaction and A novel molecular reaction mechanism of cobalt-catalyzed ESR reaction. • Co(0) site exhibiting significant preference for decomposition and water addition over aldol addition of acetaldehyde and facilitating the carbon chain shortening reaction. • Co(II) site exhibits distinct preference for dehydrogenation over dehydration of ethanol. Unraveling the roles of cobalt sites with different oxidation states is crucial for understanding mechanism of cobalt-catalyzed ethanol steam reforming (ESR) reaction. In this work, the roles of Co(0) and Co(II) sites in ESR reaction are comparatively explored by DFT calculation studies about reaction pathways over Co(1 0 0) and CoO(1 0 0) surfaces, and a novel molecular reaction mechanism has been provided. The results demonstrate that the Co(II) site in Co-based catalyst exhibits distinct preference for dehydrogenation over dehydration of ethanol especially in the presence of H 2 O molecule. For the conversion of acetaldehyde, the Co(0) site exhibits significant preference for decomposition and water addition over aldol addition of acetaldehyde, thus facilitating the carbon chain shortening to improve ethanol steam reforming. Therefore, the Co(0) and Co(II) sites exhibit synergistic effects on ESR reaction, especially the role of Co(0) site in selective conversion of acetaldehyde is more crucial for high-efficiency reforming of ethanol.