Revealing CO2 dissociation pathways at vicinal copper (997) interfaces

Abstract

Size- and shape-tailored copper (Cu) nanocrystals can offer vicinal planes for facile carbon dioxide (CO2) activation. Despite extensive reactivity benchmarks, a correlation between CO2 conversion and morphology structure has not yet been established at vicinal Cu interfaces. Herein, ambient pressure scanning tunneling microscopy reveals step-broken Cu nanocluster evolutions on the Cu(997) surface under 1 mbar CO2(g). The CO2 dissociation reaction produces carbon monoxide (CO) adsorbate and atomic oxygen (O) at Cu step-edges, inducing complicated restructuring of the Cu atoms to compensate for increased surface chemical potential energy at ambient pressure. The CO molecules bound at under-coordinated Cu atoms contribute to the reversible Cu clustering with the pressure gap effect, whereas the dissociated oxygen leads to irreversible Cu faceting geometries. Synchrotron-based ambient pressure X-ray photoelectron spectroscopy identifies the chemical binding energy changes in CO-Cu complexes, which proves the characterized real-space evidence for the step-broken Cu nanoclusters under CO(g) environments. Our in situ surface observations provide a more realistic insight into Cu nanocatalyst designs for efficient CO2 conversion to renewable energy sources during C1 chemical reactions.

Low-temperature dissociation of CO2 molecules on vicinal Cu surfaces

“…25 In addition, high-pressure (HP) STM shows surface roughening and formation of partially oxidized Cu nanoclusters on the Cu(997) surface during the reaction. 25 Under a NAP condition, CO 2 is also dissociated into CO and O at step sites of the Cu(100) surface at 370 K in 40 Pa CO 2 gas. 26 An important point is that oxygen remains on Cu surfaces as atomic oxygen or CO 3 under the NAP conditions, whereas oxygen coverage on the Cu(997) surface was very low (less than 0.03 ML) under the UHV conditions investigated in this study.…”

“…Note that the oxygen-exchange reaction could take place under both UHV and NAP conditions. Another possible reason for the different reaction pathways under NAP and UHV conditions might be the difference in the surface structures during the reactions; the HP-STM study shows the formation of Cu nanoclusters on the surface under the NAP conditions, 25 whereas the structural change of the Cu(997) was not observed at 80–92 K under the UHV conditions (Fig. 2).…”

“…On the Cu(997) surface between 299 K and 340 K, the CO 2 dissociation and formation of CO, O, and CO 3 are observed at a CO 2 pressure of 80 Pa. 23,24 Kim et al have revealed that the CO 2 dissociation into CO and O is also observed on Cu(997) at 300 K in the presence of 100 Pa CO 2 . 25 In addition, high-pressure (HP) STM shows surface roughening and formation of partially oxidized Cu nanoclusters on the Cu(997) surface during the reaction. 25 Under a NAP condition, CO 2 is also dissociated into CO and O at step sites of the Cu(100) surface at 370 K in 40 Pa CO 2 gas.…”

Study of CO2 Adsorption Properties on the SrTiO3(001) Surface with Ambient Pressure XPS

“…According to numerous previous studies, − oxygen vacancies or surface defects are known to be active sites, and the focus of research is often centered on increasing these defect sites. For example, the idea of the bent CO 2 model is widely adapted to explain the role of surface defects . However, according to our results, it is equally important to provide well-ordered oxygen lattice sites for the efficient CO 2 reaction, e.g., OH-free clean ordered SrTiO 3 surface.…”

“…Previously, Freund and Roberts pointed out that the lowest unoccupied molecular orbital of CO 2 molecules decreases as the O–C–O bond angle decreases, i.e., the so-called bent CO 2 is formed, under elevated pressure conditions . That is, if the angle between O–C–O can be bent on the surface under the elevated pressure, or if linearly symmetric CO 2 molecules are trapped on the surface defect sites, the distortion of the CO 2 molecules on the surface can promote the dissociation of CO 2 molecules. , Thus, the electronic structures of adsorbed CO 2 molecules can be modified by altering the bonding geometry. Previously, Baniecki et al investigated the bonding geometry and amount of charge transfer using density functional theory (DFT) calculations .…”