About

Professor Mark E. Orazem's research interests encompass a broad range of topics within electrochemical engineering. His work includes electrochemical impedance spectroscopy, corrosion including cathodic protection, current distribution in electrochemical systems, fuel cells, batteries, and mathematical modeling. These areas reflect a comprehensive focus on understanding and improving electrochemical processes and systems. Professor Orazem leads a research lab at the University of Florida's Department of Chemical Engineering, where he contributes to advancing knowledge in these fields through both experimental and theoretical approaches. His professional contact information and office location are provided for further engagement and collaboration.

Research topics

• Materials science
• Chemistry
• Computer Science
• Engineering
• Electrical engineering
• Computational physics
• Mathematical analysis
• Environmental chemistry
• Nanotechnology
• Physics
• Physical chemistry
• Statistics
• Biochemical engineering
• Biological system
• Mathematics
• Optics

Selected publications

• On interpretation of impedance spectra

  Electrochimica Acta · 2026-05-05

  articleSenior authorCorresponding
  PublisherDOI

• Electrochemical impedance spectroscopy for characterizing neural electrodes

  Current Opinion in Electrochemistry · 2026-01-03 · 1 citations

  articleOpen accessSenior author

  Electrochemical impedance spectroscopy (EIS) has been extensively employed in the field of neural stimulation over the past 25 years. This review summarizes the early applications, major contributions, rudimentary use, and recent advances of EIS in neural applications. EIS is widely used in both research and clinical neurostimulation to monitor changes in electrode impedance due to foreign body response and glial encapsulation. The key parameters for in vitro and in vivo measurements are discussed along with the guidelines for data interpretation.

  PublisherDOI

• Numerical Simulation of Pit Evolution in a Deep Geological Repository

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  The concept of Adaptive Phased Management, approved by Canadian federal authorities and implemented by the Nuclear Waste Management Organization, forms a comprehensive strategy for the long-term safe management of used nuclear fuel in Canada. 1 The used nuclear fuel will ultimately be placed within a container in a deep geological repository (DGR). Current container designs employ steel vessels with a protective copper outer layer, strategically selected to reduce corrosion damage. The copper-coated container may be subjected to various corrosion mechanisms over time as the DGR environment evolves. Specific to this work and in the early aerated environment of the DGR, efflorescing salt impurities present on the container surface may lead to the formation of an Evan’s droplet. To understand the behavior of the copper-coated container with respect to localized corrosion and ensure the effectiveness of this protection strategy, a preliminary two-dimensional axisymmetric time-dependent model for the corrosion of copper under an Evans droplet was developed. 2, 3 The mathematical model employs the finite-element method (COMSOL Multiphysics). Some unique features of the model are the inclusion of six heterogeneous and fifteen homogeneous reactions, implicit calculation of nm-scale films, and treatment of the influence of films on surface concentrations and potentials. The model shows the time-dependent localized corrosion rates and depths, calculated for an elapsed time of one hundred years. It also shows time-dependent radial distributions for current density and surface coverage of films. The influence of oxygen conditions and temperature was included, and the model accounted for the influence of films on reaction rate constants. Temperature and oxygen concentration were shown to have a strong contribution to copper corrosion. Preliminary results showed that the corrosion of copper and growth of films in the droplet was almost uniform on the electrode surface. Pitting is normally initiated by localized damage to the oxide film caused by physical cracks or chemical attacks. The evolution process of pits entails formation, growth, and re-passivation. Two methods of simulating pit evolution were developed. First, a unique approach to model pitting was developed in which boundary conditions were modified to define a simulated pit without changing finite-element meshing. Simulations were performed under the assumption that the atmospheric oxygen concentration decreased exponentially with time. The simulated pit was assumed to be created when the oxide film first formed and after it reached its maximum value, representing two extreme conditions for atmospheric oxygen concentration. For both pit formation times, simulations were performed for both small rate constants yielding kinetic control and larger rate constants trending toward oxygen-transport control. 4 The pit repassivated for each simulation performed, and the resulting pit depth ranged from 30 nm to 3,560 nm. The largest pit depth was calculated for large rate constants and for pits formed shortly after the oxide film was grown. A second approach for simulating pit evolution accounts for the dynamic growth process by combining the boundary condition method for predefined deep pits with mesh deformation physics. The mesh-deformation approach showed changes within the pit environment. The pH and oxygen concentration within the pit changed before and after pit re-passivation. Boundary-condition-modification and mesh-deformation approaches yield the same answers for repassivation time and resulting pit depth. References NWMO, “Choosing a Way Forward. The Future Management of Canada’s Used Nuclear Fuel. Final Study,” Nuclear Waste Management Organization, Toronto, Ontario, 2005. C. You, S. Briggs, and M. E. Orazem, “Model development methodology for localized corrosion of copper,” Corrosion Science, 222 (2023) 111388. C. You, Y. Chuai, S. Briggs, and M. E. Orazem, “Model for corrosion of copper in a nuclear waste repository,” Corrosion Science, 226 (2024) 111658. Y. Chuai, S. Briggs, and M. E. Orazem, “A Parametric Study of Mathematical Model for Long-Term Localized Corrosion of Copper in Canadian Deep Geological Repository,” ECS Meeting Abstracts, 2024, MA2024-02, 1701. Acknowledgement This work was supported by the Nuclear Waste Management Organization, Canada, under project 2000904.

  PublisherDOI

• Interpretation of Impedance Spectra for Neural Stimulation Devices

  ECS Meeting Abstracts · 2025-07-11

  articleSenior author

  The objective of this paper is to demonstrate the integration of electrochemical measurements for electrode properties to finite-element simulations that are used to calculate the efficacy of electrode configurations for neural stimulation. This work represents a preliminary step toward development of devices for treatment of a variety of neurologic and psychiatric disorders. Impedance spectroscopy measurements were obtained in vitro to quantify the electrode behavior in electrolytes intended to simulate in vivo applications. A three-electrode configuration was employed in which a Ag/AgCl electrode served as the reference. The measurement model program[1] was used to analyze electrochemical impedance spectroscopy (EIS) data for sputtered iridium oxide film (SIROF) micro-electrodes at potentials ranging from -0.4 to +0.6 V(Ag/AgCl) at pH=7.2. The frequency range used for the analysis was that determined to be consistent with the Kramers-Kronig relations. Interpretation of the data was enabled by truncating frequencies at which the ohmic impedance influenced the impedance. An interpretation model was developed that considered the impedance of the bare surface and the contribution of a porous component, based on the de Levie model of porous electrodes. The influence of iridium oxidation state on impedance was included. The proposed model fit all 36 EIS spectra well. The effective capacitance of the SIROF system ranged from 32mF/cm 2 at -0.4 V(Ag/AgCl) to a maximum of 93 mF/cm 2 at 0.2 and 0.4 V(Ag/AgCl). The parameters obtained by the regression analysis provide boundary conditions to be used in finite-element simulations of stimulation currents and potentials. Acknowledgement: This work was supported in part by NIH UO1 Grant Number: 1U01NS126052-01, Engineering the Neuronal Response to Electrical Microstimulation. References: [1]. W. Watson and M. E. Orazem, EIS: Measurement Model Program, Version 1.8, ECSArXiv, 2023, https://doi.org/10.1149/osf.io/g2fjm.

  PublisherDOI

• Electrochemical Impedance Spectroscopy of Sputtered Iridium Oxide Electrodes for Neural Applications

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  The performance of microelectrodes for neural stimulation is controlled by their impedance and their charge-storage capacity. Porous electrode systems such as sputtered iridium oxide film (SIROF) microelectrodes (200-2000 μm 2 ) and ultramicroelectrodes (<200 μm 2 ) exhibit electrochemical properties suitable for neural stimulation. The objective of the present work is to apply the measurement model approach pioneered by the Orazem group to impedance data collected on SIROF microelectrodes in phosphate-buffered saline as a function of applied potential. The data were collected in triplicate, allowing assessment of the stochastic error structure. The interpretation model accounts for the porous electrode structure and the influence of the iridium oxidation state transitions on the impedance response. The information gained from in vitro experiments can guide interpretation of the impedance response for similar electrodes conducted in animal or human studies. While the impedance conducted in vivo is certainly influenced by the different environment, in vitro studies facilitate interpretation of electrode-electrolyte properties, which comprise a component of impedance measurements performed in vivo. The present work demonstrates a philosophy of interpretation modeling that accounts for both the physics and chemistry of the system and the error structure of the measurements. It is common for authors reporting the properties of electrodes used in neuromodulation applications to include EIS measurements. The depth of interpretation of EIS data is often modest, and the checking and handling of measurement error absent. The methodology described in the present work is generally applicable to all electrodes used in electrical-stimulation-based neuromodulation and will provide a framework for understanding in vivo electrode behavior and informing the optimization of stimulation electrode coatings. As such, the present work has broad application to neural engineering.

  PublisherDOI

• Can interpretation of electrochemical impedance spectroscopy data be automated? Where do artificial intelligence algorithms stand?

  Current Opinion in Electrochemistry · 2025-11-21 · 1 citations

  article1st authorCorresponding
  PublisherDOI

• The Utility and Limitations of Distribution of Relaxation Times (DRT) Methods for Impedance Analysis

  Journal of The Electrochemical Society · 2025-07-01 · 14 citations

  articleOpen access1st authorCorresponding

  Distribution of Relaxation Times (DRT) models are gaining popularity among researchers employing electrochemical impedance spectroscopy, especially by those studying fuel cells. The main reason for this popularity is that DRT is deemed non-parametric, has a perceived ability to resolve processes with similar timescales, and is considered to provide a model-free description of impedance data. In this manuscript, we show that DRT results are strongly dependent on a user selected parameter and, because the DRT method assumes a specific model, the time constants obtained do not necessarily correlate with those associated with physical systems.

  PublisherDOI

• Electrochemical Impedance Spectroscopy

  The Electrochemical Society Interface · 2025-09-01 · 2 citations

  articleOpen access1st authorCorresponding

  Electrochemical impedance spectroscopy (EIS) is an integral part of electrochemical studies, with application to diverse topics such as fuel cells, batteries, corrosion, sensors, and biomedical devices. Here, we provide three contributions from leaders in the use of impedance spectroscopy.

  PublisherDOI

• <i>(Invited)</i> Electrochemical Impedance Spectroscopy for Implanted Electrodes

  ECS Meeting Abstracts · 2025-07-11

  articleSenior author

  The objective of this paper is to explore difficulties associated with electrochemical impedance measurements for electrodes implanted in the brain of a rat. Ultramicroelectrode devices were custom designed with 26 electrodes of 5 µm and 10 µm diameters (19.63 µm 2 and 78.54 µm 2 , respectively). To improve charge-storage capacity, electrodes were coated with a sputtered iridium oxide film (SIROF). The electrodes were implanted to a depth of 1700 µm in the somatosensory cortex of a rat. All animal experiments and surgeries were performed under the approval and guidance of the Institutional Animal Care and Use Committee (IACUC) of the University of Florida. Impedance measurements were performed using an Autolab PGSTAT12 potentiostat in a two-electrode configuration. Impedance measurements of UMEs were conducted and analyzed to extract electrochemical parameters and assess potential damage to the electrodes. The measurement-model technique [1] was used to quantify the stochastic error structure, to identify the optimal frequency range for regression analysis, and to identify inconsistencies with the Kramers-Kronig relations. The stochastic error structure measured in vivo was typically larger than that measured in vitro, limiting the number of parameters that could be extracted from regression analysis. An accuracy contour plot was measured to identify the suitable range of impedance values. It was essential to make these measurements for the system under study as the wires used to contact the device added substantially to the parasitic capacitance attributed to the leads. A process model was developed to characterize the underlying physical and chemical processes that occur at the electrode-electrolyte interface and electrode-tissue interface during neural stimulation. The process model regressed to data collected in vitro could account for the parasitic capacitance, and ohmic resistance, the constant-phase-element (CPE) behavior of the electrode, changes in the oxidation state of iridium, and reduction of oxygen. In contrast, the process model regressed to data collected in vivo could account only for the parasitic capacitance, and ohmic resistance, and the CPE behavior of the electrode. Acknowledgement: This work was supported in part by NIH UO1 Grant Number: 1U01NS126052-01, Engineering the Neuronal Response to Electrical Microstimulation. References: [1]. W. Watson and M. E. Orazem, EIS: Measurement Model Program, Version 1.8, ECSArXiv, 2023, https://doi.org/10.1149/osf.io/g2fjm.

  PublisherDOI

• Analysis of electrochemical impedance spectroscopy data for sputtered iridium oxide electrodes

  Journal of Neural Engineering · 2025-04-24 · 2 citations

  articleOpen accessSenior author

  Abstract Objective . Our objective was to perform a complete analysis of in-vitro impedance data for sputtered iridium oxide film (SIROF) micro-electrodes. The analysis included quantification of the stochastic and bias error structure and development of a process model that accounted for the chemistry and physics of the electrode–electrolyte interface. Approach . The measurement model program was used to analyze electrochemical impedance spectroscopy (EIS) data for SIROF micro-electrodes at potentials ranging from −0.4 to +0.6 V(Ag|AgCl). The frequency range used for the analysis was that determined to be consistent with the Kramers–Kronig relations. Interpretation of the data was enabled by truncating frequencies at which the ohmic impedance influenced the impedance. Main results . An interpretation model was developed that considered the impedance of the bare surface and the contribution of a porous component, based on the de Levie model of porous electrodes. The influence of iridium oxidation state on impedance was included. The proposed model fit all 36 EIS spectra well. The effective capacitance of the SIROF system ranged from 32 mF cm −2 at −0.4 V(Ag|AgCl) to a maximum of 93 mF cm −2 at 0.2 and 0.4 V(Ag|AgCl). Significance . The model developed to interpret the impedance response of neural stimulation electrodes in vitro guides model development for in-vivo studies.

  PublisherDOI

Frequent coauthors

• Bernard Tribollet

  Laboratoire Interfaces et Systèmes Électrochimiques

  150 shared

• Vincent Vivier

  Laboratoire de Réactivité de Surface

  101 shared

• Nadine Pébère

  69 shared

• Pankaj Agarwal

  KR Mangalam University

  33 shared

• Luis H. García‐Rubio

  31 shared

• Isabelle Frateur

  27 shared

• C. Deslouis

  Laboratoire Interfaces et Systèmes Électrochimiques

  22 shared

• John Newman

  21 shared

Education

• PhD, Chemical Engineering

  University of California Berkeley

  1983

• MS, Chemical Engineering

  Kansas State University

  1978

• BS, Chemical Engineering

  Kansas State University

  1976

Awards & honors

• The Electrochemical Society Corrosion Division H. H. Uhlig A…
• Herbert Wertheim College of Engineering Doctoral Dissertatio…
• Fellow of the International Society of Electrochemistry (ISE…
• Inaugural Triennial Claude Gabrielli Award, 2019
• University of Florida Foundation Preeminence Term Professor,…