Dongmei Dong

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants that require precise, field-deployable detection methods. Here, a portable extended-gate field effect transistor (EG-FET) platform was developed for the electrical detection of perfluoroalkyl acids (PFAs) in water. The carbon extended gate was functionalized with polyaniline (PANI) and Krytox-600PEG-Diamide (KPD), combining electrical transduction with fluorous enrichment of PFAs, based on the case study on legacy ionic perfluorooctanoic acid (PFOA). Comparison of four sensing layer formulations showed that increasing KPD concentration from 100 to 225 mg mL-1 more than doubled the sensitivity, while PANI provided significant improvements. The optimized PANI/KPD interface exhibited an approximately log-linear response from 10 ppm to 100 ppq and is able to resolve concentration-dependent responses across 8 orders of magnitude. Increasing PFOA concentration produced Vgs shifts in the same direction across both transistor polarities, supporting an interfacial gating mechanism. Continuous fixed-bias measurements produced prompt, concentration-dependent current changes, while other compared analytes caused only transient responses. Complementary electrochemical measurements further supported PFOA-induced changes in interfacial potential and charge transfer behavior. Finally, the sensing platform was able to distinguish treated water samples from other real-world water matrices, including lake water samples, providing PFAs response estimates. These results demonstrate the potential of the PANI/KPD EG-FET as a portable platform for practical PFAS rapid screening.

Real-time monitoring of membrane degradation is critical for enhancing the durability and reliability of proton exchange membrane fuel cells (PEMFCs). Chemical degradation of the Nafion® membrane results in the release of fluoride ions (F⁻), making F⁻ concentration a direct and quantifiable indicator of membrane health. This study presents a fluoride ion sensing system capable of continuous, in situ detection using a LaF₃ crystal-based ion-selective membrane paired with an Ag/AgCl reference electrode and integrated with a low-threshold metal-oxide semiconductor field-effect transistor (MOSFET) for signal amplification. A miniaturized bipotentiostat was used as a power supply for I-V outputs, enabling high-resolution tracking of dynamic fluoride ion fluctuations. Both a commercially available sensor and a lab-fabricated LaF₃-based sensor demonstrated stable reversible, and sensitive responses across a wide concentration range. The system effectively captured real-time changes in F⁻ concentration associated with membrane degradation, validating its suitability for operando diagnostics. The compact design, low power requirements and consistent performance of the sensor support its potential for miniaturization and direct integration into PEMFC stacks. Such embedded monitoring would enable continuous non-invasive assessment of membrane condition, early detection of degradation and predictive maintenance, ultimately extending fuel cell service life and operational efficiency.

As we strive for a sustainable future through a green hydrogen economy, it is essential to understand the degradation mechanisms of hydrogen-focused electrochemical devices, such as proton exchange membrane (PEM) fuel cells and water electrolysis systems. Our research delves into current accelerated stress tests and the resulting degradation phenomena through associated comprehensive analyses that include electrochemical, spectroscopic, tomographic, and microscopic techniques, along with detailed examinations of electrode, membrane, and interface structures. Current studies often rely on sophisticated, stationary laboratory equipment to uncover these degradation features under dynamic operations. However, for practical applications like hydrogen-powered electric vehicles, there is a critical need for a portable, low-cost, and user-friendly diagnostic tool. Given the crucial role of ion exchange and transport, nanoparticles and polymers and the potential for dissolution, monitoring, and tracking ion traces over time can provide critical insights into the behaviors within PEM-based fuel cells and water electrolysis systems. Our recent work focuses on creating electrochemical and transistor-based ion sensors integrated into a circuit chip for real-time, in-situ monitoring of system health and degradation. This effort not only aims to improve real-time diagnostics but also provides guidelines for developing suitable accelerated stress test protocols to assess system durability and for designing materials that can withstand long-term use.

In the context of proton exchange membrane fuel cells, precise monitoring of fluoride ions in the effluent water is crucial. Associated with the fluoride ion accumulation, membrane degradation and reduction of fuel cell efficiency arise. This study focuses on developing extended gate field-effect transistors (EGFET) sensors for real-time monitoring of fluoride ion concentrations. High sensitivity and specificity in detecting the concentration of fluoride ions using both N-type (TN0702) and P-type (LP0701) metal-oxide-semiconductor field-effect transistors (MOSFET) were achieved. The transfer characteristics (Id vs Vgs) owere thoroughly examined across a range of fluoride concentrations from parts per million (ppm) to parts per billion (ppb). N-type MOSFET-based sensors showed a distinct decrease in drain current (Id) with increasing fluoride concentration. With fluoride concentrations changed, the P-type MOSFET exhibited a notable shift in the threshold voltage (Vgs). A robust linear relationship was observed on calibration curves with R² values exceeding 0.90 between the natural logarithm of fluoride concentration (lnC) and gate-source voltage (Vgs). This work demonstrates that MOSFET can significantly enhance the sensitivity of electrochemical sensors without complex labeling processes. The improvement has a future in the miniaturization of cost-effective sensor systems for fuel cell applications, facilitating real-time performance and degradation monitoring.

This study explores the modeling, design, simulation, and testing of a new composite material designed for high-strength and high-temperature resistance in in-space optical mining, examining its properties at both the polymer and atomic/molecular levels. At the polymer level, the investigation includes mechanical and thermal performance analyses using COMSOL Multiphysics 6.1, employing layerwise theory, equivalent single layer (ESL) theory, and a multiple-model approach for mechanical modeling, alongside virtual thermal experiments simulating laser heating. Experimentally, porous Polyaniline (PANI) films are fabricated via electrochemical polymerization, with variations in voltage and deposition time, to study their morphology, optical performance, and electrochemical behavior. At the atomic and molecular levels, this study involves modeling the composite material, composed of Nomex, Kevlar, and Spirooxazine-Doped PANI, and simulating its behavior. The significance of this work lies in developing a novel composite material for in-space optical mining, integrating it into optical mining systems, and introducing innovative thermal management solutions, which contribute to future space exploration by improving resource efficiency and sustainability, while also enhancing the understanding of PANI film properties for in-space applications.

High-resolution topography and local potential images together are very powerful tools for understanding the local environment of nanomaterials. In electrochemistry, there are significant changes within the electrode materials upon charging and discharging. However, the surface changes for pseudocapacitive materials in repetitive electrochemical cycling are easily being overlooked. Thanks to the advances in Atomic Force Microscopy, it becomes feasible to visualize the electrical changes in surface upon charge transfer with Kelvin Probe Force Microscopy (KPFM) equipped with a conductive tip. We report the KPFM surface potential images and profiles of NiO electrochromic films upon bleaching (charging) and coloration (discharging). The measured surface potential is about 60 times higher in bleaching state upon charging at 20mC/cm². What is interesting is that the potential profile shows identical topographic features with the height profile of surface morphology. The surface particles further demonstrate shape entanglement in one direction (from ~100nm to ~140nm) and shrinkage in the orthogonal direction, suggesting the charge-induced electrical stress. According to the pseudocapacitive features in the cyclic voltammetry and electrochemical impedance spectroscopy, the surface-dominant redox behavior is within expectation. Though, this dynamic surface potential change is not well studied but important, and associated with work function fluctuations and various kinds of nanoscale charge-sensitive properties, especially for efficient electrochromic supercapacitor energy storage.

Given the focus on a green H₂ economy for a sustainable future, it is crucial to understand the degradation features of H₂-focus electrochemical devices and systems, i.e., proton exchange membrane fuel cells and water electrolysis (PEM-based FC & WE). The current accelerated stress test and resulting degradation features are systematically investigated through comprehensive analysis, including a series of electrochemical, spectroscopic, tomographic, and microscopic characterization, assisted with a detailed structure examination of the electrode, membrane, and interface. However, numerous characteristic studies that aim to uncover these features under various dynamic operations are commonly employed to depend on the sophisticated laboratory stationary bulky facilities and instruments in the theater. Moving forward to real-world practical applications, i.e., H₂ electrical vehicles, a miniaturized, mobile, low-cost, and user-friendly measurement and diagnostic tool is highly in demand. Considering the dependence of the performance and durability on the ion exchange/transport, and involvement of small particles, and the high possibility of dissolution, the time-dependent sensing and tracking of such traces of ions can provide fundamental insight into the activities and events within the PEM-based FC & WE devices and systems. Our recent efforts are dedicated to bridging the notable gap to develop electrochemical and transistor-based ion sensors integrated on a circuit chip towards real-time in-situ monitoring of the health and degradation status. This complementary work may also provide valuable guidelines for establishing a suitable accelerated stress test protocol to diagnose system durability, and for designing durable materials for long-term operation.

The electric vehicle industry has created a demand for batteries with higher power densities. The current design choice for low-weight lithium-ion battery packs for electric vehicles is to create stacks arranged in parallel or series configurations to match the power demands. The individual cells are separated and placed in a cooling duct to pull heat away from the longitudinal surface convective. The amount of cooling is dependent on the internal temperature of batteries core. The current design of the cylindrical cell is to roll the cathode, anode, and separators into a jelly roll together and attach a tab to the cathode and anode at opposite corners of the sheet. The tabs connect to the positive and negative terminals of the cell to draw current away from the cell. The tabs may act as an agent for drawing heat away from the center of the battery. Currently, commonly used cylindrical cells have a form factor of 18650, 21700, or 26650. The thermal, geometrical, and electrical properties of 18650 and 21700 cylindrical cells are studied and it is found that the 21700 cells showed additional degradation and stronger heating. Recently, companies like Tesla have produced cylindrical cells with a 4680-form factor, which is a decent way to increase the ratio of active material vs. inactive material in a cylindrical cell. However, large diameter thick cylindrical cells suffer from thermal issues. Even large format pouch cells suffer through heat trapped within the stack. Since the thermal conductivity of the anode and cathode electrodes is often near 1 W/m-K, it becomes difficult for the heat to be extracted from the center of a large-diameter cylindrical cell without forming a considerable thermal gradient. PyBaMM, an open-source mathematical modeling software written in Python programming language, has the capability to simulate different electrochemical models such as the Doyle-Fuller-Newman (DFN), Single particle model (SPM), and SPMe, and varying chemistry. The software provides easy access to the cell parameters modification and graphical user interface capabilities. The PyBaMM framework also allows to simulation lumped, isothermal, and base thermal models which are electrochemically coupled. PyBaMM uses CasADi (computer algebra systems algorithmic differentiation). The thermal gradient and heat dynamics within a porous electrode are modeled using PoreSpy and openpnm, two open-source Python libraries used to design porous networks and model physical equations such as governing heat flow, concentration gradient, and movement of water/oil through porous shale media. We have explored and combined heat dynamic models for Li-Ion cylindrical cells at both cell and electrode levels with reduced-order Doyle-Fuller-Newman electro-chemical model frameworks implemented in the PyBaMM python library. Radial temperature gradient at cell and electrode levels were both generated from simulations with a distributed parameter model as a function of electrolyte and separator thickness and thermodynamic properties. Figure 1

Despite the natural cycle of climate change being unavoidable and the reality, history has been telling the living the previous civilizations that have overstressed themselves or pushed the consumption of natural resources to the limit, and the consequence soon shows the alert in the climate. It is a critical period of time to change the current in response to climate change by employing environmentally friendly and emission-free energy technologies. The applications of advanced functional thin films ranging from the quantum level to nano and microscale, from inorganic metal oxides to conductive polymers, have been pushing the rapid development of energy-saving technologies and clean and renewable energy production, storage, and conversion in the past decade. This specific chapter focuses on fundamental- and applied- science on various advanced thin films and their applications in reliable renewable energy devices and/or systems, including but not limited to electrochromics, supercapacitors, fuel cells, flow batteries, electrolysis, triboelectricity, etc. Given that much of the work is realized across interfaces, the spotlight is shielded onto the interface of thin films in electrochemistry with different emerging cutting-edge ongoing research examples.