Role of Carbon Monoxide in Catalyst Reconstruction for CO Hydrogenation: First-Principles Study of the Composition, Structure, and Stability of Cu/Co(101̅2) as a Function of CO Pressure

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• 作者：Greg Collinge ; Norbert Kruse ; Jean-Sabin McEwen
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：February 2, 2017
• 年：2017
• 卷：121
• 期：4
• 页码：2181-2191
• 全文大小：850K
• ISSN：1932-7455

文摘

CoCu-based catalysts are promising candidates for the large-scale application of CO hydrogenation to higher alcohols with varying hydrocarbon chain length. To mimic the Co@Cu core–shell structure of nanosized CoCu particles, we choose a Cu/Co(101̅2)-oriented slab and find, in agreement with chemical imaging results, that the slab surface is always Cu-terminated, with Co underneath. Using DFT calculations, we observe major surface atom exchange in the presence of adsorbed CO, with up to 50% of the Cu atoms being replaced by Co in the straight-chain steps of the slab surface. Co atom exchange beyond 50% is not observed. More specifically, this work is accomplished by scanning the configurational space of adsorbed CO, surface Co, and surface Cu and then identifying minimum-energy surface configurations. Phase diagrams are also constructed to determine the thermodynamic driving force imposed in the presence of adsorbed CO. The inclusion of surface phonon modes is shown to ensure the correctness of the calculations. Our results reveal that geminal di- and tricarbonyl Co are formed in steps at temperatures and CO pressures relevant to catalytic CO hydrogenation. Such subcarbonyl surface structures are reminiscent of Co-carbonyl complexes encountered in coordination chemistry.