DeCaluwe Research Group
Clean Energy · Clean Water
Electrochemistry · Surface Science · Reacting Flows
My research interests focus on improving clean energy and water systems, with a particular emphasis on electrochemistry and interfaces. Via fundamental insight into the chemical, thermodynamic, and fluid mechanical processes at material interfaces and in reacting flows, we can design and improve technologies to improve quality of life for diverse populations and ease the impacts of human resource use on critical ecosystems and habitats across the globe.
Research in my group combines fundamental experiments with multi-scale numerical models to identify microstructures, surface treatments, material chemistries, or control strategies for advanced technologies. Applications include advanced lithium batteries, solid oxide and polymer electrolyte fuel cells, chemically reacting flows (chemical processing and combustion), and water filtration systems such as reverse osmosis and membrane distillation.
The figure at right gives a general overview of my research philosophy, how the different activities in my group fit together. It also illustrates the iterative nature of scientific discovery and engineering design. Discoveries at the nano-scale, for example, when evaluated in the context of device-level processes, might lead to new insights and criteria for the design and discover of new materials. Similarly, understanding the fundamental properties of materials used might lead to new ways to design, operation, and control strategies at the device level.
Current Research Projects
Cantera is an open-source suite of object-oriented software tools for problems involving chemical kinetics, thermodynamics, and/or transport processes. The software automates the chemical kinetic, thermodynamic, and transport calculations so that the users can efficiently incorporate detailed chemical thermo-kinetics and transport models into their calculations. Cantera is used predominantly in the combustion field, but also finds use in fields as diverse as electrochemistry, thin-film deposition, chemical processing, and astronomical chemistry.
The code utilizes object-oriented concepts for robust yet flexible phase models, and algorithms are generalized so that users can efficiently explore different phase models (thermodynamic, chemistry, and transport models) with minimal changes to their overall code. This helps researchers from various backgrounds incorporate relevent thermo-chemical phenomena into their work, leading to more accurate predictions and analysis. The open source nature means that anyone is free to contribute to Cantera, which accelerates the pace at which advanced scientific concepts can be incorporated into the software.
The software was conceived and created by the late Professor David Goodwin (CalTech), and has since grown to encompass a diverse team of contributors across the globe (visit the GitHub Repo for more info and to view the contributors, source code, etc.). I am one of the primary contributing developers at Cantera, where my focus is on adding new models for high-pressure reacting gases and condensed (liquid) phases and tools for electrochemistry calculations.
I am also part of an Air Force Office of Scientific Research-funded project to help develop the next generation of chemical kinetics software. This involves developing a road map and executing ground-breaking improvements in Cantera to fundamentally change the way researchers are able to incorporate chemical kinetics software into their work. This includes new types of thermodynamics and chemical models, but also new ways to extend the Cantera capabilities to interface with both fundamental and large-scale CFD code, as well as finding new ways to interact with the software so as to lower the barrier to entry for potential software users and developers.
In operando Neutron Reflectometry for Structure-property Relationships in Thin Films
This work is funded by a Department of Energy Early Career grant, which was awarded in August of 2017 and runs through August 2022. Neutron Reflectometry (NR) is a powerful technique for analyzing the thickness and chemical composition of multi-layer thin-film samples. I have used NR throughout my research to look at a range of energy materials, including degradation/passivation layers in Li-ion batteries, silicon electrodes for rechargeable batteries, and Nafion polymers for low-temperature fuel cells.
While NR is a very powerful tool for thin-films in a range of chemical environments, it is currently limited by the need for very flat substrates, which prevents looking at films and membranes with a flux across the sample. For energy storage and conversion systems, we are typically interested in how materials behave in the presence of species fluxes or when current is flowing. Understanding material properties under such non-equilibrium conditions is critical to improving device efficiency and durability.
The overall goals of this project, then, are two-fold:
Develop (design, build, and verify) a porous support compatible with NR measurements for measurements on samples in contact with two separate chemical environments, so that NR measurements can probe non-equilibrium materials in the presence of a species flux.
Use this novel test platform to understand the roles played by functional polymers (ion- and electron-conducting polymers) in PEM fuel cells and Li-oxygen batteries.
Correlating non-equilibrium NR measurements with complementary in operando, in situ and ex situ measurements and multi-scale numerical simulations will lead to new insights in both materials and device design to unlock new performance gains in energy technologies necessary for greater integration of renewables into our energy supply.
Environmental Xray Photoelectron Spectroscopy
This work, funded by an NSF Major Research Instrumentation (MRI) grant, will develop a major user facility centered on the use of "environmental" Xray Photoelectron Spectroscopy (E-XPS) to study active material interfaces.
Heterogeneous interfaces play a critical role in many engineered processes and natural systems. Active surfaces mediate multi-phase chemical reactions, often instigate fracture or failure in materials or devices, and have very sensitive responses to local environments. Because surface properties under active conditions can deviate significantly from bulk properties, the inability for many researchers to study interfacial chemical states during device operation or in relevant ambient conditions presents a substantial barrier to fundamental scientific insight.
XPS is a powerful tool for studying the chemical states of material interfaces, but these measurements are typically limited to ultra-high vacuum (UHV) and room temperatuer conditions. E-XPS enables ground-breaking insight into material properties in operating devices by allowing XPS measurements in relevant thermo-chemical environments and with optional electrical biases for non-equilibrium XPS measurements.
The Rocky Mountain Environmental XPS Facility, based on the HiPPlab from Scienta Omicron, will provide invaluable non-destructive evaluation of surface and near-surface states for materials and devices in real and operating environments, thereby overcoming the limitations of conventional, lab-based XPS at UHV conditions. The E-XPS system will allow measurements of solid-vapor and solid-liquid-vapor interfaces at pressures up to 1 mbar, temperatures up to 800°C, and can operate with electrochemical perturbation of non-equilibrated surfaces. These capabilities enable surface characterization in realistic chemical, electrochemical, and thermal environments for processes related to energy conversion, chemical processing, geochemistry, and materials degradation. The unit is also capable of "XPS imaging," which measures lateral profiles with a spatial resolution down to 5 microns.
Understanding Pore-scale Transport Phenomena in Membrane Desalination
Membrane desalination (MD) is a water purification approach that relies on the thermodynamic driving force between a warm, saline water feed and a cold, pure water retentate. In MD, a porous, hydrophobic membrane separates the two feeds. Inside the membrane pores, the water vapor pressure is higher on the warm side of the membrane than on the cold side, leading to cross-membrane diffusion of water vapor toward the retentate side.
MD has many advantages: it requires very little energy input (can be run on waste heat), can separate out a range of water contaminants, and can operate under very high salinities (i.e., it is not limited by osmotic pressure). However, poor understanding of transport limitations currently limits the efficiency and application of this technology.
This work, funded by the Burea of Reclamation's Desalination and Water Purification Research Program, seeks to understand the role of pore-scale transport phenomena on limitations in MD. The project involves first of their kind microstructural reconstruction of MD membranes via FIB-SEM analysis, which will enable high-fidelity CFD simulations of heat and mass transport on the membrane pore scale. These models, in turn, will be used to guide development of reduced-order transport models, for coupling with novel CFD simulations of channel flow to understand the interaction between pore-scale and fluid mixing pheonemena. These models, in turn, will guid development of future membranes, feed spacers, and other control strategies for improved MD performance.