Potassium‐Induced Effect on the Structure and Chemical Activity of the CuxO/Cu(1 1 1) (x ≤ 2) Surface: A Combined Scanning Tunneling Microscopy and Density Functional Theory Study

Abstract Potassium (K) plays an essential role to promote catalytic reactions in many established industrial catalytic processes. Here, we report a combined study using STM and DFT to understand the effect of the deposition of K on the atomic and electronic structures as well as chemical activities of Cu x O/Cu(1 1 1) ( x ≤2). The DFT calculations show a pseudomorphic growth of K on Cu x O/Cu(1 1 1) up to 0.19 monolayer (ML) of coverage, in which K binds the surface by a strong ionic interaction with chemisorbed oxygen and relatively weak electrostatic interactions with Cu ions, the lower and upper oxygen atoms on the Cu x O rings. The simulated STM pattern based on the DFT results agrees well with the experimental observations. The deposited K has a great impact on the surface electronic structure of Cu x O/Cu(1 1 1), which induces a significant reduction in the work function and leads to a strong electron polarization on the surface. The promotion of K on the surface binding properties is selective and varies depending on the nature of the adsorbates. According to our results, K has little effect on surface acidity but it enhances the surface basicity significantly. Consequently, the presence of K does not help CO adsorption on Cu x O/Cu(1 1 1) but is able to accelerate the activation of CO 2 . Such a promotion depends strongly on the combinations from both geometric and electronic effects. Our results highlight the origin of the promoting effect of alkali metals in the design of catalysts for complex reactions.