Bimetallic-Derived Catalytic Structures for CO₂-Assisted Ethane Activation

Journal Article · 30 August 2023 · Accounts of Chemical Research

DOI: https://doi.org/10.1021/acs.accounts.3c00348 · OSTI ID:2203711

Xie, Zhenhua  ^[1]; Chen, Jingguang G.  ^[1]

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1. Brookhaven National Laboratory (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States)

In recent years, the simultaneous upgrading of CO₂ and ethane has emerged as a promising approach for generating valuable gaseous (CO, H₂, and ethylene) and liquid (aromatics and C₃ oxygenates) chemicals from the greenhouse gas CO₂ and large-reserved shale gas. The key challenges for controlling product selectivity lie in the selective C-H and C-C bond cleavage of ethane with the assistance of CO₂. Bimetallic-derived catalysts likely undergo alloying or oxygen-induced segregation under reaction conditions, thus providing diverse types of interfacial sites, e.g., metal/support (M/M'O_x) interface and metal oxide/metal (M'O_x/M) inverse interface, that are beneficial for selective CO₂-assisted ethane upgrading. The alloying extent can be initially predicted by cohesive energy and atomic radius (or Wigner-Seitz radius), while the preference for segregation to form the on-top suboxide can be approximated using the work function, electronegativity, and binding strength of adsorbed oxygen. Furthermore, bimetallic-derived catalysts are typically supported on high surface area oxides. Modifying the reducibility and acidity/basicity of the oxide supports and introducing surface defects facilitate CO₂ activation and oxygen supplies for ethane activation. Using in situ synchrotron characterization and density functional theory (DFT) calculations, we found that the electronic properties of oxygen species influence the selective cleavage of C-H/C-C bonds in ethane, with electron-deficient oxygen over the metal (or alloy) surface promoting nonselective bond scission to produce syngas and electron-enriched oxygen over the metal oxide/metal interface enhancing selective C-H scission to yield ethylene. Here, we further demonstrate that the preferred structures of the catalyst surfaces, either alloy surfaces or metal oxide/metal inverse interfaces, can be controlled through the appropriate choice of metal combinations and their atomic ratios. Through a comprehensive comparison of experimental results and DFT calculations, the selectivity of C-C/C-H bond scission is correlated with the thermodynamically favorable bimetallic-derived structures (i.e., alloy surfaces or metal oxide/metal inverse interfaces) under reaction conditions over a wide range of bimetallic catalysts. These findings not only offer structural and mechanistic insights into bimetallic-derived catalysts but also provide design principles for selective catalysts for CO₂-assisted activation of ethane and other light alkanes. This Account concludes by discussing challenges and opportunities in designing advanced bimetallic-derived catalysts, incorporating new reaction chemistries for other products, employing precise synthesis strategies for well-defined structures with optimized site densities, and leveraging time/spatial/energy-resolved in situ spectroscopy/scattering/microscopy techniques for comprehensive structural analysis. The research methodologies established here are helpful for the investigation of dynamic alloy and interfacial structures and should inspire more efforts toward the simultaneous upgrading of CO₂ and shale gas.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
• Grant/Contract Number: SC0012704
• OSTI ID: 2203711
• Report Number(s): BNL--224932-2023-JAAM
• Journal Information: Accounts of Chemical Research, Journal Name: Accounts of Chemical Research Journal Issue: 18 Vol. 56; ISSN 0001-4842
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English