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Ganesan, Arvind

Publications and source records attributed to Ganesan, Arvind.

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Novel Q-Carbon Anodes for Sodium-Ion Batteries

The lack of a standard anode for sodium-ion batteries (SIBs) has greatly hindered their applications. Herein, we show that a novel phase of carbon, namely Q-carbon, is an effective anode material for sodium-ion batteries. The Q-carbon, which is a metastable phase of carbon consisting of about 80% sp 3 - and 20% sp 2 -bonded carbon, is synthesized by nonequilibrium pulsed laser annealing and arc-discharge methods. Two types of Q-carbons, Q1 and Q2, were evaluated as anode material for SIBs. Q1 had a slow quench and was used as the control, whereas Q2 was Q-carbon with a rapid quenching. Q1 exhibits a high initial columbic efficiency of 81% and a low-capacity retention of less than 60%, whereas Q2 has a low initial columbic efficiency of 58% and a high-capacity retention of 81%. Q2 exhibits a stable capacity of 168 mAh·g −1 at a cycling rate of C/3 (124 mA·g −1 ), which is comparable to other hard carbon anodes reported in the literature. This unique synthesis method opens a pathway for the further tuning of Q-carbon with higher trapping/charging of Na + ions in improved SIBs.

25 ENERGY STORAGE↗
DOE OSTI2024

Cascade CO 2 Insertion in Carbanion Ionic Liquids Driven by Structure Rearrangement

The CO 2 chemisorption in state-of-the-art sorbents based on oxide/hydroxide/amine moieties is driven by strong chemical bonding formation in the carbonate/bicarbonate/carbamate products, which in turn leads to high energy input in sorbent regeneration. In addition, the CO 2 uptake capacity was limited by the active sites’ utilization efficiency, with each active site incorporating one CO 2 molecule or less. In this work, a new concept and generation of sorbent was developed to achieve cascade insertion of multiple CO 2 molecules by leveraging structure rearrangement as the driving force, leading to in situ generation of extra CO 2 -binding sites and significantly reduced energy input for CO 2 release. The designed ionic liquids (ILs) containing carbanions with conjugated and asymmetric structure, deprotonated (methylsulfonyl)acetonitrile ([MSA]) anion, allowed the cascade insertion of two CO 2 molecules via consecutive C–C and O–C bond formations. The proton transfer and structure rearrangement of the carboxylic acid intermediates played critical roles in stabilizing the first integrated CO 2 and generating extra electron-rich oxygen sites for the insertion of the second CO 2 . The structure variation and reaction pathway were confirmed by operando spectroscopy, magnetic resonance spectroscopy (NMR), mass spectroscopy, and computational chemistry. The energy input in sorbent regeneration could be further reduced by harnessing the phase-changing behavior of the carbanion salts in ether solutions upon reacting with CO 2 , avoiding the energy consumption in heating the solvent. In conclusion, the fundamental insights obtained herein provide a promising approach to greatly improve the CO 2 sorption performance via sophisticated molecular-scale structural engineering of the sorbents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Porous Liquids: Versatile Fusion of Porosity and Fluidity

Porous liquids and fluids with permanent porosity have been explored over the past decade as transformative functional materials for several sustainable chemical processes. This perspective tracks the evolution of porous liquids and summarizes recent advances in the development of porous liquids for several applications, such as sorptive separations, catalysis, etc. Finally, the latter section discusses the prospects of porous liquids in several novel applications (bio applications, gas storage, heat insulation) and machine learning guided pathways for task-specific design and synthesis of porous liquids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Tailoring the Gating Effect of Organic Cage via a Porous Liquid Approach

Porous liquids (PLs) represent a new frontier in material design combining the merits of solid porous host and liquid phase in gas separation and catalysis. Herein, the PL construction approach is harnessed to tailor the gating effect of organic cages toward enhanced gas separation. A type-II fluorinated PL (F-PL) is developed via liquifying a fluorinated organic cage (F-cage) by a fluorinated ionic liquid (F-IL). The F-cage is featured by a small window size (≈5.1 Å), high surface area, good stability under highly ionic conditions, and abundant fluorine moieties. The F-IL possesses high steric hindrance (bulky cation) and structure similarity with the F-cage (fluorinated alkyl chain in the anion). The existing status structure integrity of F-cage in F-IL upon F-PL formation is illustrated via spectroscopy and X-ray-based techniques. The existence of rigid voids in F-PL is illustrated by positron annihilation lifetime spectroscopy (PALS) and the improved gas uptake capacity than F-IL via pressure-swing CO 2 uptake isotherms (0–40) bar. Further, the comparison of the gas uptake behavior (CO 2 , N 2 , CH 4 , and Xe) of F-PL and F-cage, combining the computational simulation, highlights that the PL construction can be leveraged to tune the window size of porous scaffolds, leading to enhanced gas selectivity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Unveiling the porosity effect of superbase ionic liquid-modified carbon sorbents in CO 2 capture from air

Direct air capture (DAC) of CO 2 represents one of the most promising technologies to achieve negative carbon emissions. In this work, the superbase ionic liquids (ILs)-modified carbon substrates were developed for DAC of CO 2 by harnessing the strong CO 2 binding capability of IL and the ordered porous channels of the carbon supports. Detailed porosity analysis revealed that the IL with an aromatic cation and an oxygenate anion preferred to fill the micropores, and a thin layer was created on the surface of the mesopores. Strong π-π interaction between the IL layer and the carbon surface was disclosed by wide-angle X-ray scattering (WAXS) analysis, leading to enhanced thermal stability of the IL phase. For the same lL coating amount, the DAC of CO 2 evaluation revealed that a larger mesopore size and pore volume in the carbon/IL composite materials led to higher CO 2 uptake capacity by exposing more active sites to integrate CO 2 from diluted sources. Further, the thermodynamic analysis confirmed the critical role of IL coating in providing strong chemisorption sites and significantly improved selectivity to enrich the diluted CO 2 from the air atmosphere. This work provides guidance on leveraging the scaffolds' surface properties and porosities of the scaffolds to optimize DAC of CO 2 behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Supramolecular Complexation-Enhanced CO 2 Chemisorption in Amine-Derived Sorbents

A supramolecular complexation approach is developed to improve the CO 2 chemisorption performance of solvent-lean amine sorbents. Operando spectroscopy techniques reveal the formation of carbamic acid in the presence of a crown ether. Here, the reaction pathway is confirmed by theoretical simulation, in which the crown ether acts as a proton acceptor and shuttle to drive the formation and stabilization of carbamic acid. Improved CO 2 capacity and diminished energy consumption in sorbent regeneration are achieved.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Structure Evolution of Chemically Degraded ZIF-8

Exposure of the metal–organic zeolitic imidazolate framework-8 (ZIF-8) to humid SO x gas cleaves Zn–N bonds, leading to framework disorder and a corresponding decrease in pore accessibility. This work shows that framework disorder exhibits a critical behavior with respect to water concentration in the gas stream. While the quantity of sulfate adsorbed at Zn nodes is at or below the detection threshold for the X-ray pair distribution function technique, precluding direct observation of the adsorbate, powder diffraction reveals clear structural alterations. Here, the onset of linker cleavage correlates to a large microstrain that diminishes as framework disorder increases. Energy-dispersive X-ray spectroscopy shows that the sulfur distribution throughout representative grains is uniform, implying the structure transformation is homogeneously nucleated and not dependent upon gas diffusion kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Controlled Demolition and Reconstruction of Imidazolate and Carboxylate Metal–Organic Frameworks by Acid Gas Exposure and Linker Treatment

The metal-linker coordination bond in metal–organic frameworks (MOFs) can be unstable in humid and acid gas environments, leading to loss of crystallinity and porosity. This degradation is not necessarily irreversible; solvent-assisted crystal redemption (“SACRed”) has been shown to recover the physical and chemical properties of ZIF-8 exposed to humid SO 2 . This approach can also be useful in creating mixed-linker materials that might be challenging to produce via de novo synthesis. Here, we expand more generally the concept of controlled degradation of a MOF with acid gas, followed by treatment with a fresh linker solution, to the use of different template MOFs (ZIFs, UiO-66, and UiO-67) and acid gases (SO 2 and NO 2 in dry and humid conditions). Significant losses in porosity and crystallinity along with structural changes (acid gas-linker complexes and linker functionalizations) are observed in the acid gas-exposed MOF templates, and SACRed is shown to reconstruct these partially demolished MOFs with a high degree of structural recovery. Detailed structural and spectroscopic characterizations of the controlled degradation and subsequent recovery are presented and analyzed. Furthermore, these findings indicate the generality of controlled degradation and reconstruction as a means for linker replacement in a wider variety of MOFs and also create the potential for linker substitutions (with non-native linkers) to obtain new hybrid MOFs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗