Recent Articles
Emily Traver, Jamie E. Stark, Gianna Aleman Milán, and Heather A. Andreas, "Using pH Indicator To Demonstrate Supercapacitor Reactions" Journal of Chemical Education, 2019, 96, 1778−1781.
A. Allison and H. A. Andreas, “Minimizing the Nyquist-plot semi-circle of pseudocapacitive manganese oxides through modification of the oxide-substrate interface resistance”, Journal of Power Sources, 2019, 426 93–96.
Felicia Licht, Gianna Aleman Milán and Heather A. Andreas, “Bringing Real-World Energy Storage Research into a Second-year Physical Chemistry Lab”, Journal of Chemical Education, 2018, 95, 2028−2033.
M. A. Davis and H. A. Andreas, “Improved Manganese Oxide Electrochemical Capacitor Performance Arising from a Systematic Study of Film Storage/Drying Effects on Electrochemical Properties”, Electrochimica Acta, 2018, 292, 147-156.
M. A. Davis and H. A. Andreas, “Identification and Isolation of Carbon Oxidation and Charge Redistribution as Self-discharge Mechanisms in Reduced Graphene Oxide Electrochemical Capacitor Electrodes”, Carbon, 2018, 139, 299-308.
Justin Tom, Philip J. Jakubec and Heather A. Andreas, “Enhanced Hemoglobin Electroactivity on Carbon in Electrolytes or Binders Containing Water-miscible Primary Alcohols”, Sensors & Actuators: B. Chemical, 2018, 272, 425–432.
Justin Tom, Philip J. Jakubec, and Heather A. Andreas, “Mechanisms of Enhanced Hemoglobin Electroactivity on Carbon Electrodes upon Exposure to a Water-Miscible Primary Alcohol”, Analytical Chemistry, 2018, 90, 5764−5772.
Justin Tom and Heather A. Andreas, “The Influence of Carbon-oxygen Surface Functional Groups of Carbon Electrodes on the Electrochemical Reduction of Hemoglobin”, Carbon, 2017, 112, 230-237.
Alicia M. Oickle, Justin Tom and Heather A. Andreas, “Carbon Oxidation and its Influence on Self-discharge in Aqueous Electrochemical Capacitors”, Carbon, 2016, 110, 232-242.
Michelle A. MacDonald and Heather A. Andreas‡, “Impact of Electrochemical Impedance Spectroscopy Experimental Variables on Adsorbed Protein Films, as Illustrated by Bovine Serum Albumin”, Electroanalysis, 2015, 27, 1944-1951.
Heather A. Andreas, “Self-Discharge in Electrochemical Capacitors: A Perspective Article”, Journal of the Electrochemical Society, 2015, 162 (5), A1-A7.
Heather A. Andreas, Jennifer M. Black, and Alicia M. Oickle, “Self-discharge in Manganese Oxide Electrochemical Capacitor Electrodes in Aqueous Electrolytes with Comparisons to Faradaic and Charge Redistribution Models”, Electrochimica Acta, 2014, 140, 116-124.
Michelle A. MacDonald and Heather A. Andreas, “Method for Equivalent Circuit Determination for Electrochemical Impedance Spectroscopy Data of Protein Adsorption on Solid Surfaces”, Electrochimica Acta, 2014, 129, 290-299.
- In this work we incorporate a color indicator as indirect evidence for the manganese oxide’s pseudocapacitive reaction (MnO2 + H+ + e− ⇌ MnOOH) for our 2nd-year Undergraduate supercapacitor lab. Using the evidence of pH changes (the methyl red goes from light yellow to red during an oxidative potential hold), students can make the link between oxidation state changes and the applied potential of the electrochemical experiment. We optimize the indicator concentration and electrochemical parameters to ensure the color changes are evident. Optimal responses arise when 15 μM methyl red is coupled with a 2 min, 0.8 V potentiostatic hold.
A. Allison and H. A. Andreas, “Minimizing the Nyquist-plot semi-circle of pseudocapacitive manganese oxides through modification of the oxide-substrate interface resistance”, Journal of Power Sources, 2019, 426 93–96.
- Often, though not universally, the Nyquist plots of pseudocapacitive materials evidence a semi-circular feature, which is typically attributed to the pseudocapacitive reaction's charge-transfer resistance. However, we show, for the first time, that the origin of the semi-circle is in fact the oxide-substrate interface resistance. The interface is varied through heat treatment of the manganese oxide and by electrodepositing the manganese oxide on different metals. Additionally, our novel manganese oxide double-deposition – in which a thin layer of manganese oxide on the interface is heat treated but the bulk of the film is hydrous – separates the interface and pseudocapacitive responses. Films with a low interface resistance (e.g., with a heat-treated interface or deposited on Pt) evidence a 98% smaller semi-circle than those with a poor interface (films deposited on stainless steel with no heat treatment). Conversely, there is no correlation between the amount of psuedocapacitance and semi-circle size. Thus, the Nyquist semi-circle is associated with the interface resistance, and proper modification of this interface can reduce the performance limitations associated with this resistance.
Felicia Licht, Gianna Aleman Milán and Heather A. Andreas, “Bringing Real-World Energy Storage Research into a Second-year Physical Chemistry Lab”, Journal of Chemical Education, 2018, 95, 2028−2033.
- This work describes an easy-to-implement undergraduate lab to study supercapacitors. This energy-storage-related lab has no air- or water-sensitivity (unlike most labs relating to batteries), introduces 2nd-year physical chemistry students to energy-related terms, such as energy, power and charge, and gives these students skills that translate into real energy-storage industry and research.
M. A. Davis and H. A. Andreas, “Improved Manganese Oxide Electrochemical Capacitor Performance Arising from a Systematic Study of Film Storage/Drying Effects on Electrochemical Properties”, Electrochimica Acta, 2018, 292, 147-156.
- A systematic study relating manganese oxide film storage/drying to a full gamut of EC properties and figures of merit, with the aim of enhancing these properties and addressing this oxide’s well-known stability issues. The knowledge gained allows for an intelligent choice of storage/drying condition based on the desired electrochemical and physical parameters and can facilitate comparisons between literature results where different storage/drying conditions are used. An innovative new double-deposition film synthesis is introduced incorporating both heat treatment and wet storage – films produced through this method demonstrate the optimal properties achieved from heat treatment and wet storage with none of their drawbacks. Our novel double-deposition method can easily be applied to other pseudocapacitive materials, and ideally improve their performance and expand their range of applications.
M. A. Davis and H. A. Andreas, “Identification and Isolation of Carbon Oxidation and Charge Redistribution as Self-discharge Mechanisms in Reduced Graphene Oxide Electrochemical Capacitor Electrodes”, Carbon, 2018, 139, 299-308.
- This work is the first to systematically examine rGO self-discharge in acidic aqueous electrolytes for use as electrochemical capacitor electrodes. We identify, for the first time, two main self-discharge mechanisms: charge redistribution and carbon oxidation. Because separation of activation-controlled self-discharge reactions and charge redistribution is difficult, we also strategically designed and then implemented an novel experimental protocol to separate the contribution from these two self-discharge mechanisms.
Justin Tom, Philip J. Jakubec and Heather A. Andreas, “Enhanced Hemoglobin Electroactivity on Carbon in Electrolytes or Binders Containing Water-miscible Primary Alcohols”, Sensors & Actuators: B. Chemical, 2018, 272, 425–432.
- We demonstrate the commonly overlooked impact of water‑miscible primary alcohols on hemoglobin (Hb) electroactivity. We show a twofold higher Hb response when the Nafion binder contains alcohol, indicating the alcohol significantly changes Hb electroactivity. Significant changes are seen for alcohol concentrations as low as 10%. When binders are necessary for a Hb-containing film, a low methanol content is preferred; ethanol and propanol should be avoided. Conversely, Hb quantification is 53x higher in alcohol-containing electrolytes, due to changes to both the Hb and carbon. Methanol-containing electrolyte exhibits an ultra-low 0.78 nM Hb detection limit (twofold lower than any previously reported for solution-based Hb detection).
Justin Tom, Philip J. Jakubec, and Heather A. Andreas, “Mechanisms of Enhanced Hemoglobin Electroactivity on Carbon Electrodes upon Exposure to a Water-Miscible Primary Alcohol”, Analytical Chemistry, 2018, 90, 5764−5772.
- Exposing a carbon electrode to hemoglobin (Hb) and alcoholic solvents, such as methanol, ethanol or 1-propanol, drastically changes Hb electroactivity. In this research we show that these alcohols impact Hb electroactivity via three mechanisms: modification of the carbon surface oxides on the glassy carbon (GC) electrode, Hb film formation, and structural changes to Hb. Knowledge of these mechanisms shows the impact of alcohols on both Hb and carbon electrodes, allows for thoughtful design of the Hb-sensing system, is vital for proper analysis of Hb electroactivity in the presence of these alcohols (e.g. when used as binder solvents for immobilizing Hb into films) and provides fundamental understanding of the Hb-carbon interactions.
Justin Tom and Heather A. Andreas, “The Influence of Carbon-oxygen Surface Functional Groups of Carbon Electrodes on the Electrochemical Reduction of Hemoglobin”, Carbon, 2017, 112, 230-237.
Alicia M. Oickle, Justin Tom and Heather A. Andreas, “Carbon Oxidation and its Influence on Self-discharge in Aqueous Electrochemical Capacitors”, Carbon, 2016, 110, 232-242.
Michelle A. MacDonald and Heather A. Andreas‡, “Impact of Electrochemical Impedance Spectroscopy Experimental Variables on Adsorbed Protein Films, as Illustrated by Bovine Serum Albumin”, Electroanalysis, 2015, 27, 1944-1951.
Heather A. Andreas, “Self-Discharge in Electrochemical Capacitors: A Perspective Article”, Journal of the Electrochemical Society, 2015, 162 (5), A1-A7.
Heather A. Andreas, Jennifer M. Black, and Alicia M. Oickle, “Self-discharge in Manganese Oxide Electrochemical Capacitor Electrodes in Aqueous Electrolytes with Comparisons to Faradaic and Charge Redistribution Models”, Electrochimica Acta, 2014, 140, 116-124.
Michelle A. MacDonald and Heather A. Andreas, “Method for Equivalent Circuit Determination for Electrochemical Impedance Spectroscopy Data of Protein Adsorption on Solid Surfaces”, Electrochimica Acta, 2014, 129, 290-299.