Adsorption of CO₂ and Coadsorption of H and CO₂ on Potassium‐Promoted Cu(115)

Abstract

The influence of potassium, in the submonolayer regime, on the adsorption and coadsorption of CO2 and H on a stepped copper surface, Cu(115), has been studied by photoelectron spectroscopy, temperature-programmed desorption, and work-function measurements. Based on the fast recording of C 1s and O 1s core-level spectra, the uptake of CO2 on K/Cu(115) surfaces at 120 K has been followed in real time, and the different reaction products have been identified. The K 2p3/2 peak exhibits a chemical shift of -0.4 eV with CO2 saturation, the C 1s peaks of the CO3 and the CO species show shifts of -0.8 and -0.5 eV, respectively, and the C 1s peak of the physisorbed CO2 exhibits no shift. The effects of gradually heating the CO2/K/Cu(115) surface include the desorption of physisorbed CO2 at 143 K; the desorption of CO at 193 K; the ordering of the CO3 species, and subsequently the dissociation of the carbonate with desorption at 520-700 K. Formate, HCOO-, was synthesized by the coadsorption of H and CO2 on the K/Cu(115) surface at 125 K. Formate formed exclusively for potassium coverages of less than 0.4 monolayer, whereas both formate and carbonate were formed at higher coverages. The desorption of formate-derived CO2 took place in the temperature range 410-425 K and carbonate-derived CO2 desorbed at 645-660 K, depending on the potassium coverage.

Formate stability and carbonate hydrogenation on strained Cu overlayers on Pt(111)

“…Although several studies of high-index Cu surfaces with alkalimetal promotion have been published [29,30], no investigations of formate thermal stability have to our knowledge been reported for the clean high-index surfaces. Nakamura et al [31] studied methanol synthesis on several Cu facets including the high-index surface Cu(3 1 1) and reported that formate was also present on this surface.…”

Surface chemistry of carbon dioxide revisited

“…Peak assignments for valence band spectra of (CO 2 +H)/K/Cu(115) interface obtained at T=125 -500 K. Reproduced with permission from Wiley[120].Pre-covering a K-deposited Pt(111) surface with oxygen atoms yields a similar result, as if the surface was not pre-dosed with O 2 upon CO 2 adsorption[122]. Bent anionic CO 2 species forms on the surface and readily reacts with a surface O atom to yield carbonate.…”

Photolysis of the CO2 + K/Au(111) System

“…This was first demonstrated on a K-dosed Pd(100) surface, 13,14 followed by extensive studies on Rh(111), [15][16][17] Pt(111), 18,19 Pd(111), 20,21 Ru(0001), [22][23][24] Ag(111), 25 Co(1010), 26 Mo 2 C/Mo(100), 27 Cu(110), and Cu(115). 28,29 Further enhancement of the electron transfer to CO 2 can be achieved by the illumination of adsorbed CO 2 , as was first demonstrated on the Rh(111) surface. 30 In the present paper, an account is given on the photolysis of the CO 2 + K/Au(111) system.…”