NO Reduction by Co-adsorbed Water Molecules on Cu(110)
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Catalytic reactions on surfaces consist of complex elementary processes, such as adsorption, diffusion, collision, electron/atom transfer, and desorption of molecules. The understanding of the catalytic processes at the single-molecule level has remained challenging. Heterogeneous catalysis is inherently complex, and it is difficult to follow these reactions and clarify their mechanisms. In this chapter, the reduction of NO by water on Cu(110) using STM is demonstrated, where STM was used to control and image the reaction, and to characterize the product and intermediate. A one-to-one reaction yields a characteristic NO–water complex, in which water induces partial filling of the empty \(2\pi ^*\) orbital of NO, leading to N–O bond weakening. Subsequent reaction of the complex with another water molecule induces further weakening of the N–O bond, leading to bond rupture. Furthermore, hydrogen-bond coupling is shown to induce back donation and, thus, plays a crucial role in N–O bond cleavage; this provides a fundamental insight into the catalytic reduction of NO under ambient conditions.
KeywordsHydrogen bonding Reduction of nitric oxide Scanning tunneling microscopy
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