Between my experiences as a graduate student and postdoctoral researcher, I have tackled a number of problems related to energy technology using materials science and electrochemistry techniques. I have made significant contributions to a number of different electrochemical systems, such as Li-ion batteries and Zn electrodeposition, with an eye towards the materials and surface chemistry aspects of these topics. This research has included extensive in-situ synchrotron and electron microscopy studies of electrochemical systems, performed at Brookhaven National Laboratory and IBM T.J. Watson Research Center. My particular interests are in the properties of electrochemically active material surfaces, and in the development of advanced battery technologies for use in grid storage and electric vehicle systems.
Light-Ion Batteries
Lithium-ion batteries are one of the most commonly used types of rechargeable batteries, due to their high energy and power density compared to other technologies. While working at Georgia Tech, I researched the use of silicon as an anode material to increase the energy density of Li-ion batteries. This research included fundamental research on the mechanical properties of Si-Li alloys[1], understanding the role of internal porosity in compensating electrochemical shock[2], scalable synthesis of nanomaterials with internal porosity[3], and the development of advanced, bio-inspired binder materials specifically engineered for use with Si anodes[4],[5]. The combined effect of these studies allowed me to develop advanced Si anodes that increased the overall lifespan of the Li-ion batteries I assembled from less than 10 cycles to more than 500. While the state of the art currently allows for the compensation of extreme volume changes, further improvement of the lifespan of Si anode materials to commercially viable levels required a better understanding of the properties of the solid-electrolyte interface and interactions between Si and standard Li-ion battery electrolytes, which I helped develop using a variety of different characterization techniques, such as XPS, SEM and TEM.
Since leaving Georgia Tech and beginning my work at City College of New York and Princeton University, I have extensively studied the complex phase transformations occurring in manganese dioxide, a material which has been used as a cathode material in Li-ion batteries, as well as in more experimental Na-ion[6],[7] and Mg-ion[8],[9] battery technologies. The difficulty of using manganese dioxide as a cathode material lies in the complex failure and phase transformation mechanisms of this material. In order to understand these complex reaction mechanisms, a wide range of experiments is necessary to test the various hypotheses and theories on the reactions occurring within the battery using many different characterization methods. I have used techniques as diverse as in-situ and in-operando EDXRD, performed at Brookhaven National Laboratory[10],[11], and acoustic time-of-flight measurements[12] to study the phase transformations occurring in MnO2 during cycling. These insights have proven invaluable for understanding the failure mechanisms of alkaline battery systems and extending their cycling lifetime.
The multi-directional approach I used in the past was critical for the development of advanced anodes for Li-ion batteries - my fundamental research on the mechanical properties of Si alloys and the effects of electrochemical shock guided my development of advanced nanocomposites and binder materials specifically tailored to the needs of these materials. Similarly, my in-situ and in-operando studies of MnO2 proved invaluable for understanding the failure mechanisms of alkaline cells and finding ways to compensate for them. Manganese dioxide, vanadium oxide, and other transition metal oxides and chalcogenides are potential materials for Mg-ion and Na-ion battery chemistries, but their charge storage mechanism and failure modes remain inadequately explored.[13],[14] Many of these future battery chemistries have remained completely unstudied by in-situ and in-operando techniques, and the potential for advancing understanding of these materials is great. The advantage of using a wide range of characterization technologies, such as those I have used in my previous work, is the opportunity to correlate results from different techniques to develop a better big picture of the changes occurring in the electrode during cycling. In the future, I am interested in extending these techniques to other cathode and anode materials for Li-ion batteries, such as sulfur, and to other types of “light ion” battery chemistries, such as Na- and Mg-ion technologies. I will continue my collaborations with researchers at Princeton University, Brookhaven National Laboratory, and IBM T.J. Watson Research Center, all facilities with access to extensive in-situ and in-operando characterization technologies. I will also develop in-house facilities for in-operando acoustic characterization of batteries, a novel technique that can be implemented with only a few thousand dollars worth of equipment.12 I believe that these experiments will attract attention and succeed in acquiring funding from sources such as the National Science Foundation, which has previous supported research into Mg-ion and Na-ion advanced cathodes and electrolytes, as well as the Toyota Motor Corporation, which has a particular interest in Mg-ion batteries.
Electrochemical Synthesis of Ammonia
The artificial synthesis of ammonia and ammonia compounds is essential for the industrial production of fertilizer required for modern agriculture. Up until the early 20th century, ammonia was typically either mined from naturally existing nitrate deposits or produced from calcium cyanamide using the Frank-Caro process.[15] In 1910, the Haber-Bosch process was developed for the production of ammonia from atmospheric nitrogen and hydrogen gas. While more energy-efficient than the Frank-Caro process, the Haber-Bosch process still requires relatively high temperatures (400-500 C) and pressures (15-25 MPa). These conditions are necessary primarily for increasing the activity of the iron or ruthenium catalysts used to enhance the rate of reaction of the N2 + 3H2 → 2NH3 process. This reaction is exothermic in favor of ammonia at room temperature, but the rate of reaction is extremely low, due to the strength of the N-N triple bond.[16] The catalysts act to adsorb nitrogen gas and subsequently perform scission of the N-N bond, dramatically increasing the rate of the reaction.[17] The cost of the Haber-Bosch process is further increased by the requirement for extensive purification of the N2 and H2 gas inputs to the process, as even ppm concentrations of oxygen or sulfur may poison the catalyst.[18] Additionally, the H2 input is typically produced via steam reformation of natural gas or coal, which releases carbon dioxide, increasing the environmental footprint of ammonia production.
The cost and CO2 footprint of NH3 synthesis could be dramatically reduced by the use of a catalyst for N2 reduction which does not require extreme temperatures and pressures, or even further via a process that can use water as an input, rather than hydrogen gas. The first significant progress in this field was made in 2013, when ammonia was successfully produced from air and water using a Pt/C catalyst at room temperature and pressure, albeit at low rates and poor (<1%) Faradaic efficiency.[19] Attempts to find non-Pt catalysts for low-temperature electrochemical ammonia synthesis since then have met with limited success. I would like to investigate new energy efficient catalysts for electrochemical ammonia synthesis at ambient temperature and pressure. Energy-efficient electrolytic ammonia production could potentially replace the existing, highly capital intensive and polluting ammonia synthesis infrastructure with a network of distributed-scale, near-point-of-use production plants using renewable electricity sources. I believe I can contribute to the development of this technology via my expertise in materials synthesis/characterization and surface chemistry. Relatively little work has been done in this field on sophisticated nanostructured materials. Nanostructured composites have already been extensively applied for use in the well-developed field of oxygen reduction catalysts, including promising results in areas such as nanoclusters[20] and 2D materials[21]. Composite materials of this type, such as those I developed as electrode materials in my work on Li-ion and alkaline batteries, could potentially be used in electrochemical ammonia synthesis. My research in this field has used both more traditional top-down techniques, where electrochemically inactive materials are etched away to produce rationally designed composite materials2, as well as bottom-up methods, where a hierarchical self-assembly process produces carefully engineered nanomaterials without wasteful subtractive manufacturing processes.3 My work in developing doped manganese-based oxide11 and carbonate[22] cathode materials for use in alkaline batteries may also prove applicable to electrochemical ammonia synthesis. Manganese oxide materials have been extensively studied for oxygen reduction reactions and other catalytic processes, but not for this new field. I believe that electrochemical ammonia synthesis is a research topic with a great deal of room for future growth. As part of my research in this area, I would pursue collaborations with researchers at Brookhaven National Laboratory, Princeton University, and IBM T.J. Watson Research Center, which both possess highly advanced materials characterization and imaging facilities, as well as sophisticated facilities for studying materials surface properties. I would also pursue collaborations with researchers at Stevens Institute of Technology itself, whose Chemical Engineering & Materials Science department has many researchers with extensive expertise in catalysis processes. The catalysis expertise of the Catalytic Nanoparticles Lab and the reactor assembly expertise of the NJ Center for Microchemical Systems would be particularly helpful. I believe that these experiments would be successful in attracting funding from the Department of Energy’s ARPA-E program, which has funded a number of electrochemical ammonia synthesis projects in the past, as well as from the Department of Agriculture, which has previously supported electrochemical reactor projects related to nitrogen fertilizer science.
[1] Hertzberg, B., et al. (2011). Ex-situ depth-sensing indentation measurements of electrochemically produced Si–Li alloy films. Electrochem Comm, 13(8), 818-821.
[2] Hertzberg, B., Alexeev, A., & Yushin, G. (2010). Deformations in Si− Li Anodes Upon Electrochemical Alloying in Nano-Confined Space. J Am Chem Soc, 132(25), 8548-8549.
[3] Magasinski, A., et al. (2010). High-performance lithium-ion anodes using a hierarchical bottom-up approach. Nature Mat, 9(4), 353-358.
[4] Kovalenko, I., et al. (2011). A major constituent of brown algae for use in high-capacity Li-ion batteries. Science, 334(6052), 75-79.
[5] Magasinski, A., et al. (2010). Toward efficient binders for Li-ion battery Si-based anodes: polyacrylic acid. JACS App Mater & Interfaces, 2(11), 3004-3010.
[6] Slater, M.D., et al. (2013) Sodium‐ion batteries. Adv. Func. Mat. 23(8), 947-958.
[7] Tompsett, D.A., and Islam, M.S. (2013) Electrochemistry of Hollandite α-MnO2: Li-Ion and Na-Ion Insertion and Li2O Incorporation. Chem. Mater. 25(12), 2515-2526.
[8] Zhang, R., et al. α-MnO2 as a cathode material for rechargeable Mg batteries. (2012) Electrochem. Comm. 23, 110-113.
[9] Sun, X., et al. (2016) Investigation of the Mechanism of Mg Insertion in Birnessite in Nonaqueous and Aqueous Rechargeable Mg-Ion Batteries. Chem. Mater. 28(2), 534-542.
[10] Gallaway, J.W., et al. (2015) Hetaerolite Profiles in Alkaline Batteries Measured by High Energy EDXRD. J. Electrochem. Soc. 162(1), A162-A168.
[11] Hertzberg, B., et al. (2016) Effect of Multiple Cation Electrolyte Mixtures on Rechargeable Zn-MnO2 Alkaline Battery. Chem. Mater. 28(13), 4536-4545.
[12] Bhadra, S., et al. (2015) Anode Characterization in Zinc-Manganese Dioxide AA Alkaline Batteries Using Electrochemical-Acoustic Time-of-Flight Analysis. J. Electrochem. Soc. 163(6), A1050-A1056.
[13] Palomares, V. et al. (2012) Na-ion batteries, recent advances and present challenges to become low cost energy storage systems. Energy & Environmental Science 5(3), 5884-5901.
[14] Levi, E., et al. (2009) On the Way to Rechargeable Mg Batteries: The Challenge of New Cathode Materials. Chem. Mater. 22(3), 860-868.
[15] Haber, Fritz. The synthesis of ammonia from its elements Nobel Lecture, June 2, 1920. Resonance 7(9), 86-94.
[16] Jennings, J. Richard, ed. Catalytic ammonia synthesis: fundamentals and practice. Springer Science & Business Media, 2013.
[17] Ertl, G. (1983) Primary steps in catalytic synthesis of ammonia. J. Vac. Sci. Tech. A 1(2), 1247-1253.
[18] Waugh, K. C., et al. (1994) The mechanism of the poisoning of ammonia synthesis catalysts by oxygenates O2, CO and H2O: an in situ method for active surface determination. Cat. Letters 24(1), 197-210.
[19] Lan, Rong, et al. (2013) Synthesis of ammonia directly from air and water at ambient temperature and pressure. Nat. Sci Rep 3
[20] Zhang, Mengmeng, et al. (2015) Hybrid of porous cobalt oxide nanospheres and nitrogen-doped graphene for applications in lithium-ion batteries and oxygen reduction reaction. J. Pow. Sources 290, 25-34.
[21] Liang, Yongye, et al. "Co3O4 nanocrystals on graphene as a synergistic catalyst for oxygen reduction reaction." Nature materials 10.10 (2011): 780-786.
[22] Hertzberg, Benjamin, et al. (2014) A manganese-doped barium carbonate cathode for alkaline batteries. J. Electrochem. Soc. 161(6), A835-A840.