The various types of acetaldehyde adsorption on clean, and on modified Rh(111) surface

The capture, the transformation of CO₂ into C₁ and into C₂ compounds is environmentally and economically important issue. Noble metals, including Rh, are effective catalyst in the synthesis of CO+H₂ into C₂-oxygenates [1]. Acetaldehyde, (AA) is also important as a hydrogen carrier as it could be an easy H₂ storage, carrier compound. In addition, AA has been found as a product also in the decomposition of ethanol on metal surfaces [2]. The interaction of CH₃CHO with Rh(111) surface has been investigated by AES, EELS, TDS and work function methods [3]. The chemisorbed acetaldehyde (adsorbed at 100 K ) starts to decompose at 200 K. The main products are adsorbed CO and desorbed CH₄ (Tp=260K ). Minor products are adsorbed H and C. A weakly adsorbed CH₃CHO desorbs in a sharp peak centered at 150 K. Oligomerised acetaldehyde was also found ( [CH3CHO]_n⁺ , 1<n<5 ) in the gase phase with Tp=225-235 K. In the chemisorbed layer ₁-(O)-CH₃CHO_a and ₂-(O,C)-CH₃CHO_a have been observed. Electronegative and electro positive modifiers may influence the stability of these surface complexes such as i.) surface carbon acts as a simple contaminant and decreases the adsorption of CH₃CHO by site blocking mechanism. ii) a direct surface reaction with oxygen led to the formation of acetate. iii) adsorbed potassium increased the thermal stability of acetaldehyde by an extended electronic interaction. The electronic transfer from potassium to the AA orbitals can be suggested as it was obtained in the interaction of K with HCOOH on Rh(111) [4].

Refrences:

[1] A. Kiennemann, R.Breault, J-P. Hinderman, M. Laurin; Chem. Soc. Faraday Trans. 1 1987 83, 2119

[2] Z. Ferencz, A. Erdőhelyi, K. Baán, A. Oszkó, L. Óvári, Z. Kónya, C. Papp, H-P. Steinrück, J. Kiss; ACS Catal. 2014, 4, 1205-1218

[3] I. Kovács, A. P. Farkas, Á. Szitás, Z. Kónya, J. Kiss; Surf. Sci. 2017, 664,

[4] I. Kovács, J. Kiss, Z. Kónya; Catalysts 2020, 10, 675