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5. 2D Metal/Graphene and 2D Metal/Graphene/Metal Systems for Electrocatalytic Conversion of CO2 to Formic Acid.

Author

Cho, Jinwon, Medina, Arturo, Saih, Ines, Il Choi, Ji, Drexler, Matthew, Goddard, William A., Alamgir, Faisal M., and Jang, Seung Soon

Subjects
*FORMIC acid, *METALLIC films, *METALLIC thin films, *METALLIC surfaces, *GRAPHENE, *METALS
Abstract

Efficiently transforming CO2 into renewable energy sources is crucial for decarbonization efforts. Formic acid (HCOOH) holds great promise as a hydrogen storage compound due to its high hydrogen density, non‐toxicity, and stability under ambient conditions. However, the electrochemical reduction of CO2 (CO2RR) on conventional carbon black‐supported metal catalysts faces challenges such as low stability through dissolution and agglomeration, as well as suffering from high overpotentials and the necessity to overcome the competitive hydrogen evolution reaction (HER). In this study, we modify the physical/chemical properties of metal surfaces by depositing metal monolayers on graphene (M/G) to create highly active and stable electrocatalysts. Strong covalent bonding between graphene and metal is induced by the hybridization of sp and d orbitals, especially the sharp dz2 ${{d}_{{z}^{2}}}$ , dyz ${{d}_{yz}}$ , and dxz ${{d}_{xz}}$ orbitals of metals near the Fermi level, playing a decisive role. Moreover, charge polarization on graphene in M/G enables the deposition of another thin metallic film, forming metal/graphene/metal (M/G/M) structures. Finally, evaluating overpotentials required for CO2 reduction to HCOOH, CO, and HER, we find that Pd/G, Pt/G/Ag, and Pt/G/Au exhibit excellent activity and selectivity toward HCOOH production. Our novel 2D hybrid catalyst design methodology may offer insights into enhanced electrochemical reactions through the electronic mixing of metal and other p‐block elements. [ABSTRACT FROM AUTHOR]

Published
2024
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31. High-yield electrochemical hydrogen peroxide production from an enhanced two-electron oxygen reduction pathway by mesoporous nitrogen-doped carbon and manganese hybrid electrocatalysts

Author

Byeon, Ayeong, primary, Cho, Jinwon, additional, Kim, Jong Min, additional, Chae, Keun Hwa, additional, Park, Hee-Young, additional, Hong, Seok Won, additional, Ham, Hyung Chul, additional, Lee, Seung Woo, additional, Yoon, Ki Ro, additional, and Kim, Jin Young, additional

Published
2020
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34. Importance of Exsolution in Transition-Metal (Co, Rh, and Ir)-Doped LaCrO3 Perovskite Catalysts for Boosting Dry Reforming of CH4 Using CO2 for Hydrogen Production

Author

Oh, Joo Hyeng, primary, Kwon, Byeong Wan, additional, Cho, Jinwon, additional, Lee, Chan Hyun, additional, Kim, Min Kyeong, additional, Choi, Sun Hee, additional, Yoon, Sung Pil, additional, Han, Jonghee, additional, Nam, Suk Woo, additional, Kim, Jin Young, additional, Jang, Seung Soon, additional, Lee, Ki Bong, additional, and Ham, Hyung Chul, additional

Published
2019
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35. Structural Transformation of a Multicompartment Micelle Induced by Photo-Switchable Spiropyran–Merocyanine Transition: Dissipative Particle Dynamics Simulation Approach

Author

Cho, Jinwon, Choi, Ji Il, and Jang, Seung Soon

Abstract

This work highlights the structural transformation of a multicompartment micelle consisting of an amphiphilic A-b-(C-spiropyran) diblock copolymer in water, induced by the photo-switched transition between hydrophobic nonionic spiropyran and hydrophilic zwitterionic merocyanine, using a set of computational methods such as density functional theory (DFT), molecular dynamics (MD) simulation, and dissipated particle dynamics (DPD) simulation. By employing a new computational framework for the Flory–Huggins χ-parameter, which is improved by considering solvation free energy, it is demonstrated that the χ-parameter for a merocyanine–water pair is significantly smaller than that for a spiropyran–water pair, indicating that hydrophobic spiropyran becomes hydrophilic merocyanine through the photo-switched transition. Our computational procedure of χ-parameter calculation is further validated by investigating the deprotonation of syndiotactic and isotatic acrylic acid in water. It is revealed that a reasonable χ-parameter of −0.717 and −1.23 can be calculated from a singly deprotonated syndiotactic and isotatic trimer acrylic acid in water, respectively, which is consistent with the weak acidity of acrylic acid. Finally, using a set of calculated χ-parameters, DPD simulations are performed employing two different block copolymers with two different block lengths: A10-b-(C6-Spiro12) (Micelle I) and A6-b-(C10-Spiro12) (Micelle II), demonstrating that both micelles undergo distinctive inside-out transformations as a function of the block length ratio. Through the structure analysis, it turns out that Micelle I keeps a well-defined core–shell structural feature before and after the transformation, whereas Micelle II loses such structural feature because short Block A is not capable of forming the core of micelle.

Published
2024
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36. Palladium Single‐Atom Catalysts Supported on C@C3N4 for Electrochemical Reactions.

Author

Kim, Hee‐Eun, Lee, In Hyuk, Cho, Jinwon, Shin, Sangyong, Ham, Hyung Chul, Kim, Jin Young, and Lee, Hyunjoo

Subjects
EXTENDED X-ray absorption fine structure, CATALYST supports, PALLADIUM catalysts, SCANNING transmission electron microscopy, OXIDATION of formic acid, HECK reaction, PRECIOUS metals
Abstract

Single atom catalysts (SACs) maximize the utilization of noble metal whereas nanoparticle catalysts have inner metal atoms unavailable. In this study, various electrocatalytic reactions were investigated for Pd and Pt SACs. The single atoms were immobilized on thin layers of graphitic carbon nitride with carbon black (for simplicity, C@C3N4) to produce an electrochemically efficient and stable SACs. Single atomic structure was confirmed by high‐angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) and extended X‐ray absorption fine structure (EXAFS) analyses. Oxygen reduction reaction (ORR) and CO stripping experiments were conducted, and the results were compared with the corresponding nanoparticle catalysts. Lack of ensemble sites in the SACs resulted in two‐electron pathway for ORR; single atomic Pd on C@C3N4 (C@C3N4−Pd1) showed high activity and selectivity for H2O2 formation. DFT calculations showed that C@C3N4−Pd1 follows a downhill path for H2O2 formation unlike single atomic Pt on C@C3N4 (C@C3N4‐Pt1), resulting in enhanced H2O2 selectivity. Weaker adsorption of oxygen intermediates on C@C3N4−Pd1 resulted in enhanced ORR activity. The SACs showed no interaction with CO as confirmed by no CO stripping peak. This resulted in no activity for formic acid oxidation following indirect pathway or methanol oxidation, which necessitates COads as reaction intermediates. SACs can be efficient electrocatalysts with high activity and unique selectivity. [ABSTRACT FROM AUTHOR]

Published
2019
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39. Creation of discrete active site domains viamesoporous silica poly(styrene) composite materials for incompatible acid–base cascade reactionsElectronic supplementary information (ESI) available. See DOI: 10.1039/d0cy01988g

Author

Cleveland, Jacob W., Kumar, Dharam Raj, Cho, Jinwon, Jang, Seung Soon, and Jones, Christopher W.

Abstract

This work highlights the design and synthesis of bifunctional mesoporous silicate – polymer composite dual acid–base supported cascade catalysts. Compartmentalization of the two incompatible active sites is sought by segregating acid sites on the silica surface, and base sites within polymer chains and/or polymer domains. The ability to isolate and segregate active sites viacontrol of the mesoporous silica pore size and polymer molecular weight is probed with silica samples functionalized by a grafting-to process. Supplemental activator and reducing agent (SARA) atom transfer radical polymerization is used to synthesize random copolymers containing protected primary amines. Thiol–ene ‘click’ chemistry facilitates silica functionalization viaa convergent approach, with the ene-functionalized polymer end group and silica-grafted thiols forming SBA/MCM-SH-poly(styrene-co-2-(4-vinylbenzyl)isoindoline-1,3-dione). Polymer deprotection and thiol oxidation produces primary amine/sulfonic acid containing composite catalysts. With the polymer supported Lewis base and silica grafted Brønsted acid, the two-step deacetalization – Knoevenagel condensation cascade is explored to assess the ability of these polymer/silica hybrids to segregate active sites, allowing both acid and base site accessibility. Six composite catalysts are synthesized and tested in individual and cascade reactions with kinetic results demonstrating that lower molecular weight SBA-15-P1 and MCM-41-P1 catalysts outperform (higher turnover frequencies and initial rates) their higher molecular weight analogues, as well as a polymer-free system containing molecular active sites dispersed on the silica surface. Higher molecular weight composite catalysts perform more poorly due to limited chain solubility, mass transfer limitations, and poor catalyst accessibility. In many cases, the polymer chains effectively thread into the mesopores, with higher molecular weight polymers leading to pore blockage and inhibited mass transfer.

Published
2021
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46. Importance of Exsolution in Transition-Metal (Co, Rh, and Ir)-Doped LaCrO3Perovskite Catalysts for Boosting Dry Reforming of CH4Using CO2for Hydrogen Production

Author

Oh, Joo Hyeng, Kwon, Byeong Wan, Cho, Jinwon, Lee, Chan Hyun, Kim, Min Kyeong, Choi, Sun Hee, Yoon, Sung Pil, Han, Jonghee, Nam, Suk Woo, Kim, Jin Young, Jang, Seung Soon, Lee, Ki Bong, and Ham, Hyung Chul

Abstract

LaCrO3perovskite and transition-metal (Co, Rh, Ir)-doped perovskite-based catalysts were fabricated using the Pechini method and applied to the dry reforming reaction of CH4using CO2. One of the prepared perovskite-based catalysts, the LaCr0.95Ir0.05O3−δcatalyst, showed the highest CH4conversion (81%) at 750 °C via the preactivation of the catalyst with H2gas. It also showed highly stable catalytic activity for 72 h without coke formation on the catalyst surface. Through X-ray photoelectron spectroscopy and transmission electron microscopy analyses, it is confirmed that the improved catalytic activity of the LaCr0.95Ir0.05O3−δperovskite-based catalyst was based on the exsolution of Ir nanoparticles on the catalyst surface, which catalyzes the cleavage of the C–H bond for CH4. Density functional theory calculations revealed that the exsolution of a dopant Ir in LaCr0.95Ir0.05O3−δis more exothermic with/without an oxygen vacancy condition by 1.01 eV/0.43 eV, which suggests the agglomeration of Ir on the surface.

Published
2019
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50. Ca2CuO3: A high temperature CO2sorbent with rapid regeneration kinetics

Author

Hassani, Ehsan, Cho, Jinwon, Feyzbar-Khalkhali-Nejad, Farshad, Rashti, Ali, Jang, Seung Soon, and Oh, Tae-Sik

Abstract

Three different calcium-based ternary oxide sorbents, Ca2CuO3, Ca3Co4O9, and Ca2Fe2O5, were characterized as potential sorbents for CO2capture. The behaviors of these sorbents were compared to CaO under various CO2concentrations via temperature programmed carbonation/decarbonation. Ca2CuO3and Ca3Co4O9showed lower inversion temperatures, while Ca2Fe2O5had a higher inversion temperature than CaO. In addition, the copper and cobalt containing sorbents showed relatively narrower temperature windows going from the highest carbonation rate to the highest decarbonation rate. This narrow temperature window can be advantageous in operating a temperature swing process. Ca3Co4O9and Ca2Fe2O5showed low conversion. Under the best-case scenario, the conversion of these sorbents was less than 25%. Ca2CuO3showed faster regeneration compared to CaO when the sorbent temperature was cycled between 700 and 800 °C. In addition, we found 740–850 °C for Ca2CuO3and 640–900 °C for CaO as the temperature swing windows of the best reaction rates. The narrower range of operational temperature (110 °C for Ca2CuO3compared to 260 °C for CaO) can lead to higher overall rate of CO2uptake and release. Ca2CuO3showed 60% higher cycle-averaged decarbonation rate compared to CaO when cycled between the temperatures of maximum carbonation and decarbonation rates

Published
2022
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