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The water–gas shift reaction (CO+H2O→CO2+H2) is a step in many industrial processes, including ammonia and hydrogen production, with potential use in coal conversion schemes as well. It is traditionally achieved on copper- or iron-based catalysts. We have studied the kinetics of this reaction at pressures of ∼40 Torr on a Cu(111) single-crystal surface characterized by pre- and post-reaction surface analyses (Auger electron spectroscopy, x-ray photoelectron spectroscopy, low-energy electron diffraction). Specific rates, activation energies, and reaction orders are consistent with measurements on supported Cu catalysts. The results are interpreted in terms of a mechanism whereby the reaction rate is limited by the dissociative adsorption of water. We have also characterized the sulfur poisoning of this catalyst, which appears to occur by a simple site-blocking mechanism, where the reaction ensemble size is small (≤2 Cu atoms). Finally, we have found that Cs addition (from aqueous CsOH) enhances the reaction rate by a factor of 15. The structure of the catalyst surfaces will be discussed. After reaction, the unpromoted Cu surfaces were always completely metallic, and no surface oxygen was observable. This was true even if the Cu was heavily oxidized before reaction. With Cs addition, oxygen was always observable after reaction, and its level was roughly proportional to the Cs concentration, with an oxygen:cesium atomic ratio near unity. The mechanism of Cs promotion is discussed.

ligand-based radical anion, arid the solubility of the polymerized metal complex units.(4) The polymerization efficiency, approaches but never exceeds unity. This argues for hydrodimerization, and against a chain-growth mechanism, as the dominant pathway for monomer coupling.(5) Charge-transport rates, film morphology, and dry-film conductivity measurements show the ((py)2C2)-based films to be similar to other metallopolymer films prepared by EP but not to poly (acetylene).

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