Grad school work

2025

Microkinetic Models of Electrochemistry: Assumptions, Limitations, and Failures

CFY, Cui, Y., Tartakovsky, D.M. J. Phys. Chem. C. 129(38), 17080–17090, 2025

Accurate models of electrochemical reactions at the interface between active material and electrolyte are essential for battery design and management. Current models of electron transfer processes, i.e., the Butler–Volmer equation and the Marcus–Hush–Chidsey (MHC) model, differ in their range of validity but both fail for high overpotentials and high C-rates. We show that these models, and the related Marcus theory, rely on small-parameter expansions and inadequately treat the strong interactions between inner-sphere electrochemical reactions occurring at high C-rates. By systematically detailing all assumptions made in the development of these models, we demonstrate the utility of a targeted phenomenological approach in extending these models. As a case study, we relax the wide-band approximation used in MHC to tame the inaccuracy in modeling the oxidative branch of the lithium plating/stripping reaction. Finally, for convenience, we present all models discussed in a consistent form which explicitly includes their concentration dependence, as required by macroscopic battery simulators.

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Journal	JPCC

2024

Multi-moiré trilayer graphene: Lattice relaxation, electronic structure, and magic angles

CFY, May-Mann, J., Zhu, Z., and Devakul, T. Phys. Rev. B. 110(11), 115434, 2024

We systematically explore the structural and electronic properties of twisted trilayer graphene systems. In general, these systems are characterized by two twist angles \(\theta_{12}\) and \(\theta_{23}\), which lead to two incommensurate moiré periods. We show that when the ratio of twist angles is close to a simple fraction, \(\theta_{12}/\theta_{23}=\pm1\), or \(−1/2\), strong lattice relaxation results in the formation of domains of periodic single-moiré structures. For other rational pairs of twist angles, we find that relaxation is weak, leading to incommensurate moiré periods and an overall quasicrystalline structure. We identify experimentally relevant magic angles at which the electronic density of states is sharply peaked and strongly correlated physics is most likely to be realized.

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Preprint	arXiv:2310.12961
Publication	PRB

Undergrad work

2025 (2019)

Process for purifying semiconducting single-walled carbon nanotubes

Ding, J., Li, Z., CFY, Malenfant, P.R.L., and Ouyang, J. WO/2025/054694, 2025.

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Patent	IPC
Slides	PDF download

Slides are from a seminar I gave for an undergrad class. At one point, I had made the purest sc-SWCNTs in the world (4N purity). That was two field changes, three degrees, six years, and eight PIs before this was finally granted.

2022

Micropatterned PDMS stamps for spatially selective dry transfer of mechanically exfoliated flakes

CFY, Lyons, J.W., Hunt, B.M. Presented at the APS March Meeting, Chicago, IL, March 16, 2022.

PDMS+polymer transfer slides are one of the primary tools for making van der Waals heterostructures from exfoliated flakes using a dry transfer process. However, such transfer slides are typically made from either flat stamps or round droplets of PDMS, whose macroscopic size makes it difficult to selectively pick up flakes in a crowded environment. A ready solution can be drawn from the field of microfluidics, where micropatterned SU-8 or silicon are used as molds to form fine details on the surface of PDMS stamps for techniques such as microcontact printing. We will discuss the efficacy of using such PDMS micropatterning to construct ten-micron scale features to improve the spatial selectivity of the dry transfer process.

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APS March Meeting 2022	Abstract M71.8
Slides	PDF download
Poster	PDF download

Poster from undergrad department symposium. Fabrication methods from slide 7 is summarized in slide 14, mechanism in slide 12. A fab project so easy that even I could do it! Who needs a cleanroom, anyway?

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