Co and h2o interactions on model pt/cu, pt/ceo2/cu, cuxo/cu and cusnoy/cu catalyst surfaces: UHV to near-ambient conditions

Heterogeneous catalysts play a crucial role in industrial applications including chemical production, clean energy, environmental sustainability, and renewable energy. Improving catalyst stability, efficiency, and selectivity requires understanding the surface properties and molecule-surface interactions that affect the reaction mechanisms. Here, using a surface science approach, we studied model catalyst surfaces and individual parameters that govern reaction mechanisms and can affect the adsorption/desorption and catalytic active sites. First, step-edge/terrace site decoration and site exchange of Pt atoms with a stepped Cu(211) surface were investigated by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) under ultra-high vacuum (UHV). At low Pt coverage, step decoration and site exchange with Cu were identified as two pathways for isolating Pt as single atoms. The binding energy of CO was found to strongly depend on Pt coverage. Heteroatomic Pt–Cu bonding can modify the CO binding energy on both Cu and Pt, reducing the desorption temperature of CO adsorbed on Pt. Water adsorption studies on Cu(211) and Pt/Cu(211) surfaces show that water adsorbs more strongly on Cu step sites, promoting partial dissociation and OH formation. On fully Pt-decorated Cu(211) step sites, water adsorbs molecularly, and the chain structures formed by water and OH on Cu(211) are disrupted by Pt. Then, CO and CO2 adsorption characteristics on the Pt/CeO2/Cu(111) model catalyst were investigated to gain insight into the interaction between Pt nanoparticles and the CeO2 support surface. The deposition of CeO2 at 700 K results in island formation on the Cu(111) surface, whereas at 520 K it leads to a more continuous film formation. An enhancement in CO and CO2 uptakes was observed on reduced CeO2-x. Pt nanoparticles deposited on these surfaces remained in a metallic form and facilitated the oxidation of CO to form CO2 by utilizing lattice oxygen in the Pt and CeO2 interface. Catalyst surface behavior under UHV can differ significantly from that under realistic, higher-pressure conditions. To study CuxO reduction behavior, synchrotron-based techniques were employed at near-ambient pressure (~1 mbar). The interaction of CO with CuxO/Cu(211) and CuxO/Cu(111) surfaces was investigated using time-resolved X-ray photoelectron spectroscopy (XPS) and IRRAS. Carbonyl and carbonate species formation was observed while exposing the CuxO/Cu(211) surface to CO, which was not detectable on CuxO/Cu(111). Low-coordinated metallic Cu might serve as active sites for breaking the interatomic bond in molecular CO and promote the formation of carbonate species through direct CO dissociation and CO disproportionation simultaneously. SnOy local clusters can stabilize Cu+ and prevent its reduction through the formation of Sn–O–Cu bonding sites. However, the reduction of SnOy/CuxO/Cu(211) starts at a lower pressure compared to SnOy/CuxO/Cu(111) surface, which can be attributed to the presence of steps on the surface.