Understanding the Surface Structure and Catalytic Activity of SnO_x/Au(111) Inverse Catalysts for CO₂ and H₂ Activation

Journal Article · 02 March 2022 · Journal of Physical Chemistry. C

DOI: https://doi.org/10.1021/acs.jpcc.2c00138 · OSTI ID:1854092

Kang, Jindong  ^[1]; Rui, Ning  ^[2]; Rosales, Rina ^[1]; Tian, Yi ^[1]; Senanayake, Sanjaya D.  ^[2]; Rodriguez, José A.  ^[3]

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1. State Univ. of New York (SUNY), Stony Brook, NY (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Div.
3. State Univ. of New York (SUNY), Stony Brook, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Div.

Carbon dioxide hydrogenation is a promising approach for the reduction of greenhouse gas pollution via the production of fuels and high-value chemicals utilizing C1 chemistry. In this process, the activation of nonpolar molecules, CO₂ and H₂, at mild conditions is challenging. In this study, we report a well-defined inverse SnO_x/Au(111) catalyst that shows the ability to activate both CO₂ and H₂ at room temperature. Scanning tunneling microscopy (STM) and ambient pressure X-ray photoemission spectroscopy (AP-XPS) are combined to understand the surface structure, growth mode, chemical state, and activity of SnO_x/Au(111) surfaces. Nanostructures of SnO_x at the sub-monolayer level were prepared by depositing Sn on Au(111) followed by O₂ oxidation. For the as-prepared SnO_x/Au(111), two-dimensionally formed SnO_x thin films on a Au(111) substrate were observed with STM of two different moieties, discernible based on their height: clusters (~0.4 Å) and nanoparticles (NPs, 1–2.5 Å), which are assigned to Sn–Au alloys and SnO_x, respectively, in corroboration with XPS analysis. Furthermore, SnO_x/Au(111) was annealed under UHV to test its thermal stability. Upon annealing at 400–600 K, a disappearance of SnO_x NPs and reappearance of highly dispersed Sn clusters were clearly noticeable from the STM and XPS results, identifying the thermal decomposition of SnO_x and subsequent formation of Sn–Au alloys on the surface due to the recombination of Sn clusters with Au. We investigated the reactivity of the SnO_x/Au(111) surfaces toward CH₄, CO₂, and H₂. The SnO_x/Au(111) surfaces have excellent CO₂ and H₂ activation abilities even at room temperature with negligible reactivity for methane activation. Our AP-XPS results show that H₂ can be activated on the SnO_x NPs by the reduction to Sn. For CO₂, the activation and further dissociation are identified by a reoxidation of Sn with newly formed Sn–O bonds and the formation of surface carbon. Therefore, we propose that SnO_x is a potential catalyst or additive to achieve CO₂ hydrogenation under mild conditions.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012704
• OSTI ID: 1854092
• Report Number(s): BNL-222824-2022-JAAM
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 10 Vol. 126; ISSN 1932-7447
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English