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14. CO2 Conversion on N-Doped Carbon Catalysts via Thermo- and Electrocatalysis: Role of C-NO x Moieties.

Author

Hursán, Dorottya, Ábel, Marietta, Baán, Kornélia, Fako, Edvin, Samu, Gergely, Nguyën, Huu, López, Núria, Kónya, Zoltán, Sápi, András, Janáky, Csaba, and Atanassov, Plamen

Abstract

N-doped carbon (N-C) materials are increasingly popular in different electrochemical and catalytic applications. Due to the structural and stoichiometric diversity of these materials, however, the role of different functional moieties is still controversial. We have synthesized a set of N-C catalysts, with identical morphologies (∼27 nm pore size). By systematically changing the precursors, we have varied the amount and chemical nature of N-functions on the catalyst surface. The CO2 reduction (CO2R) properties of these catalysts were tested in both electrochemical (EC) and thermal catalytic (TC) experiments (i.e., CO2 + H2 reaction). CO was the major CO2R product in all cases, while CH4 appeared as a minor product. Importantly, the CO2R activity changed with the chemical composition, and the activity trend was similar in the EC and TC scenarios. The activity was correlated with the amount of different N-functions, and a correlation was found for the -NO x species. Interestingly, the amount of this species decreased radically during EC CO2R, which was coupled with the performance decrease. The observations were rationalized by the adsorption/desorption properties of the samples, while theoretical insights indicated a similarity between the EC and TC paths.

Published
2022

23. Three-dimensional Printing of Complex Graphite Structures

Author

Sajadi, Seyed Mohammad, Enayat, Shayan, Vásárhelyi, Lívia, Alabastri, Alessandro, Lou, Minghe, Sassi, Lucas M., Kutana, Alex, Bhowmick, Sanjit, Durante, Christian, Kukovecz, Ákos, Puthirath, Anand B., Kónya, Zoltán, Vajtai, Robert, Boul, Peter, Tiwary, Chandra Shekhar, Rahman, Muhammad M., and Ajayan, Pulickel M.

Subjects
Condensed Matter - Materials Science
Abstract

Graphite, with many industrial applications, is one of the widely sought-after allotropes of carbon. The sp2 hybridized and thermodynamically stable form of carbon forms a layered structure with strong in-plane carbon bonds and weak inter-layer van der Waals bonding. Graphite is also a high-temperature ceramic, and shaping them into complex geometries is challenging, given its limited sintering behavior even at high temperatures. Although the geometric design of the graphite structure in many of the applications could dictate its precision performance, conventional synthesis methods for formulating complex geometric graphite shapes are limited due to the intrinsic brittleness and difficulties of high-temperature processing. Here, we report the development of colloidal graphite ink from commercial graphite powders with reproducible rheological behavior that allows the fabrication of any complex architectures with tunable geometry and directionality via 3D printing at room temperature. The method is enabled via using small amounts of clay, another layered material, as an additive, allowing the proper design of the graphene ink and subsequent binding of graphite platelets during printing. Sheared layers of clay are easily able to flow, adapt, and interface with graphite layers forming strong binding between the layers and between particles that make the larger structures. The direct ink printing of complex 3D architectures of graphite without further heat treatments could lead to easy shape engineering and related applications of graphite at various length scales, including complex graphite molds or crucibles. The 3D printed complex graphitic structures exhibit excellent thermal, electrical, and mechanical properties, and the clay additive does not seem to alter these properties due to the excellent inter-layer dispersion and mixing within the graphite material., Comment: 19 pages, 4 figures

Published
2020

39. Photocatalytic CO2 Reduction

Author

Sápi, András, Thangavel, Rajkumar, Yadav, Mohit, Kiss, János, Kukovecz, Ákos, Kónya, Zoltán, He, Liang-Nian, Series Editor, Tundo, Pietro, Series Editor, Zhang, Z. Conrad, Series Editor, Garg, Seema, editor, and Chandra, Amrish, editor

Published
2022
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