Browsing by Author "Taylor, Erin E."

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Does boron or nitrogen substitution affect hydrogen physisorption on open carbon surfaces?
(Royal Society of Chemistry, 2022-01) Rowsey, Rylan; Taylor, Erin E.; Hinson, Ryan W.; Compton, Dalton; Stadie, Nicholas P.; Szilagyi
Incorporation of heteroatoms in carbon materials is commonly expected to influence their physical or chemical properties. However, contrary to previous results for methane adsorption, no technologically significant effect was identified for the hydrogen physisorption energies (measured 4.1–4.6 kJ mol−1 and calculated qst = −ΔHads = 4.1 ± 0.7 kJ mol−1 using a comprehensive set of levels of theory) as a function of B- and N-substitution of a mid-plane C-site on open carbon surfaces.
Methane Adsorption on Heteroatom-Modified Maquettes of Porous Carbon Surfaces
(American Chemical Society, 2021-07) Rowsey, Rylan; Taylor, Erin E.; Irle, Stephan; Stadie, Nicholas P.; Szilagyi, Robert K.
Experimental and theoretical studies disagree on the energetics of methane adsorption on carbon materials. However, this information is critical for the rational design and optimization of the structure and composition of adsorbents for natural gas storage. The delicate nature of dispersion interactions, polarization of both the adsorbent and the adsorbate, interplay between H-bonding and tetrel bonding, and induced dipole/Coulomb interactions inherent to methane physisorption require computational treatment at the highest possible level of theory. In this study, we employed the smallest reasonable computational model, a maquette of porous carbon surfaces with a central site for substitution and methane binding. The most accurate predictions of methane adsorption energetics were achieved by electron-correlated molecular orbital theory CCSD(T) and hybrid density functional theory MN15 calculations employing a saturated, all-electron basis set. The characteristic geometry of methane adsorption on a carbon surface (“lander approach”) arises due to bonding interactions of the adsorbent π-system with the proximal H–C bonds of methane, in addition to tetrel bonding between the antibonding orbital of the distal C–H bond and the central atom of the maquette (C, B, or N). The polarization of the electron density, structural deformations, and the comprehensive energetic analysis clearly indicate a ∼3 kJ mol–1 preference for methane binding on the N-substituted maquette. The B-substituted maquette showed a comparable or lower binding energy than the unsubstituted, pure C model, depending on the level of theory employed. The calculated thermodynamic results indicate a strategy for incorporating electron-enriched substitutions (e.g., N) into carbon materials as a way to increase methane storage capacity over electron-deficient (e.g., B) modifications. The thermochemical analysis was revised for establishing a conceptual agreement between the experimental isosteric heat of adsorption and the binding enthalpies from statistical thermodynamics principles.
Methodological Studies of the Mechanism of Anion Insertion in Nanometer‐Sized Carbon Micropores
(Wiley, 2022-11) Welty, Connor; Taylor, Erin E.; Posey, Sadie; Vailati, Patric; Kravchyk, Kostiantyn V.; Kovalenko, Maksym V.; Stadie, Nicholas P.
Dual-ion hybrid capacitors (DIHCs) are a promising class of electrochemical energy storage devices intermediate between batteries and supercapacitors, exhibiting both high energy and power density, and generalizable across wide chemistries beyond lithium. In this study, a model carbon framework material with a periodic structure containing exclusively 1.2 nm width pores, zeolite-templated carbon (ZTC), was investigated as the positive electrode for the storage of a range of anions relevant to DIHC chemistries. Screening experiments were carried out across 21 electrolyte compositions within a common stable potential window of 3.0–4.0 V vs. Li/Li+ to determine trends in capacity as a function of anion and solvent properties. To achieve fast rate capability, a binary solvent balancing a high dielectric constant with a low viscosity and small molecular size was used; optimized full-cells based on LiPF6 in binary electrolyte exhibited 146 Wh kg−1 and >4000 W kg−1 energy and power densities, respectively.
Prominent Structural Dependence of Quantum Capacitance Unraveled by Nitrogen‐Doped Graphene Mesosponge
(Wiley, 2023-12) Tang, Rui; Aziz, Alex; Yu, Wei; Pan, Zheng‐Ze; Nishikawa, Ginga; Yoshii, Takeharu; Nomura, Keita; Taylor, Erin E.; Stadie, Nicholas P.; Inoue, Kazutoshi; Kotani, Motoko; Kyotani, Takashi; Nishihara, Hirotomo
Porous carbons are important electrode materials for supercapacitors. One of the challenges associated with supercapacitors is improving their energy density without relying on pseudocapacitance, which is based on fast redox reactions that often shorten device lifetimes. A possible solution involves achieving high total capacitance (Ctot), which comprises Helmholtz capacitance (CH) and possibly quantum capacitance (CQ), in high-surface carbon materials comprising minimally stacked graphene walls. In this work, a templating method is used to synthesize 3D mesoporous graphenes with largely identical pore structures (≈2100 m2 g−1 with an average pore size of ≈7 nm) but different concentrations of oxygen-containing functional groups (0.3–6.7 wt.%) and nitrogen dopants (0.1–4.5 wt.%). Thus, the impact of the heteroatom functionalities on Ctot is systematically investigated in an organic electrolyte excluding the effect of pore structures. It is found that heteroatom functionalities determine Ctot, resulting in the cyclic voltammetry curves being rectangular or butterfly-shaped. The nitrogen functionalities are found to significantly enhance Ctot owing to increased CQ.
What Structural Features Make Porous Carbons Work for Redox-Enhanced Electrochemical Capacitors? A Fundamental Investigation
(American Chemical Society, 2021-02) Zhao, Yang; Taylor, Erin E.; Hu, Xudong; Evanko, Brian; Zeng, Xiaojun; Wang, Hengbin; Ohnishi, Ryohji; Tsukazaki, Takaki; Li, Jian-Feng; Stadie, Nicholas P.; Yoo, Seung Joon; Stucky, Galen D.; Boettcher, Shannon W.
The addition of redox-active molecules into electrochemical-capacitor electrolytes provides increased specific energy density. Here we illustrate the underlying operational mechanisms and design principles for carbons with hierarchical pore sizes in the micropore (0.6–2 nm) to mesopore (2–3 nm, 5–30 nm) range as electrode materials in redox-enhanced electrochemical capacitors. When using iodide as a model redox additive, we discover that the redox capacity is correlated to the pore volume of the carbon electrodes when void space is included. The fastest rates are typically observed with pore-sizes >1 nm, while slow self-discharge requires pores <1 nm. When used without an ion-selective-membrane separator, the delivered capacity correlated with the quantity of redox species held within the carbon. A commercial microporous carbon, MSC30, with substantial hierarchy in pore size, including small <0.8 nm pores and larger 1.1–3 nm pores, showed the best overall performance, illustrating key design principles.