(6de) Charge Storage and Transport in Electrochemical Science: From Bulk to Interfaces

Seeking clean energy is one of the most urgent problems humanity is facing. As far as cleanness and efficiency are concerned, electrochemical technologies for energy storage and conversion can offer reliable and sustainable solutions in this endeavor.

My research interests focus on fundamental understanding of electrochemical processes, which essentially refers to thermodynamics, kinetics, and transport of materials. As electrode materials typically are required to convey both electrons and ions, their thermodynamics are driven by the electrochemical potentials of charge species. Such a framework holds not only for bulk phases but also at the interface of materials. By performing experimental characterizations and theoretical calculations, I have comprehensively studied the storage phenomena for energy materials. To elucidate the storage mechanisms, I developed a generalized model that describes the fundamental relation between the storage capacity and the component activity [1]. The developed model is in a good agreement with experimental evidences for metal storage (Li and Ag) and for gas storage (H₂) [2,3].

Equally important to thermodynamics is kinetics. It determines the charging speed of energy storage devices, e.g. batteries, or the power density of energy conversion devices, e.g. fuel cells. I am particularly interested in studying kinetic problems at heterointerfaces. A recent work showed that a prototype composite consisting of a superionic conductor and an electronic conductor exhibits an unprecedentedly fast kinetics in Ag storage. The rate characterized by chemical diffusion exceeds any other solids at room temperature, and even exceeds the rate of NaCl in liquid water [4]. The finding of this study may open a new class of composite materials that allow for ultrafast energy delivery.

Aside from energy storage and conversion technologies, I am also interested in irreversible electrochemical processes, e.g. corrosion. My previous works investigated the mechanism of carbon corrosion induced by molten salts, a critical reaction governing the practical efficiency of direct carbon fuel cells. The in situ observation showed that the carbon corrosion kinetics is strongly correlated with the wetting behavior of molten salts [5]. This work together with a modeling study were later adopted by a fuel cell company to optimize the design of electrode reactors.

Selected publications:

[1] C.-C. Chen and J. Maier, Space charge storage in composites: thermodynamics, Physical Chemistry Chemical Physics, 19, 6379-6396 (2017)

[2] C.-C. Chen and J. Maier, Decoupling electron and ion storage and the path from interfacial storage to artificial electrodes, Nature Energy, 3, 102–108 (2018)

[3] L. Fu, C.-C. Chen, et al., Thermodynamics of lithium storage at abrupt junctions: Modeling and experimental evidence, Physical Review Letters, 112, 208301, 1–5 (2014)

[4] C.-C. Chen, L. Fu, and J. Maier, Synergistic, ultrafast mass storage and removal in artificial mixed conductors, Nature, 536, 159–164 (2016)

[5] C.-C. Chen, et al., Wetting behavior of carbon in molten carbonate, Journal of The Electrochemical Society, 159, D597–D604 (2012)

Teaching Interests:

I have broad interests in teaching the Chemical Engineering coursework, including thermodynamics, transport, reaction kinetics, interface science, and electrochemistry. At Stanford University, I served as a guest lecturer in a renewable energy class. My goal was to teach thermodynamics, kinetics, and transport phenomena in energy technologies. To this end, I developed an instructive set of materials and structured the lecture in a manner that the students can clearly see the connection between the fundamental knowledge and the real-world applications. During my PhD study, I also mentored several graduate students working on different projects.