The Leddy Group's research efforts span a few different areas but all share a foundation in electroanalytical chemistry and spin polarization. Our specific areas of research are magnetically-modified power sources (batteries and fuel cells) and kinetic studies of magnetically-modified composite materials processes, electrochemical investigation of nitrogenase enzyme to enhance ammonia production, characterization of mass transport in films, and thin layer sonoelectrochemistry. In addition, we model these systems mathematically and with computer simulations.

electrochemistry diagram

Magnetically Modified Systems

Magnetic fields do not affect chemical systems through thermodynamic and equilibrium processes, but through mass transport and kinetics. Magnetic fields open new reaction pathways to alter rates and product distributions. Our studies of magnetic field effects on chemical kinetics run from the fundamentals of theory and modeling through experimental demonstration and evaluation of effects in composite materials to implementation in technologies such as fuel cells and batteries.


Magnetic effects on kinetics arise through spin polarization. For reactions between two radicals (species with unpaired electrons), magnetic fields can couple electron spins to facilitate electron transfer rates as much as nine-fold in typical laboratory fields (~10 T); this occurs through electron spin polarization. For reactions between a radical and singlet (species with no unpaired electrons), magnetic effects arise through electron nuclear spin polarization. The field couples the radical electron spin and the singlet nuclear spin. While magnetic effects on reactions between radicals have been known for ~30 years, we have only recently demonstrated effects on radical singlet . In a low field (0.2 T), cross exchange rates can be enhanced ~103.

Composite Materials

Our earlier work focused on the relationship between microstructure and properties in composite materials. Composites are formed of an ion exchange polymer, such as Nafion, and a second, inert microstructured component. For magnetic systems, the second component is magnetic microparticles. Electrochemical methods are used to measure electron transfer rates of redox species in the composites and to demonstrate current enhancements approaching 3000%. Studies of composites provide design paradigms for tailoring better composite materials and membrane separators. With magnetic composites, models of magnetic effects are tested and better fuel cells are designed.

Fuel Cells and Batteries

Fuel cells provide power through electrochemical oxidation of a fuel. As electrical devices, fuel cells are not restricted by Carnot limitations and can in theory be 100% efficient. Because of their efficiency, refueling (not recharging), and environmental advantages, fuel cells are attractive power sources for devices ranging from cars to laptops. Proton exchange membrane (PEM) fuel cells consist of two electrodes separated by an ion exchange polymer; a fuel is provided to the anode and oxygen or air is the oxidant at the cathode. For hydrogen fuel, there are three difficulties: hydrogen poses safety hazards; proton-bound water traverses the membrane to flood the cathode and dry the anode; and oxygen reduction kinetics are poor. For organic or reformate fuel, more severe liabilities arise through passivation of the noble metal catalysts by species such as carbon monoxide. As oxygen is paramagnetic and magnetic composites are an appropriate environment in which to enhance kinetics, magnetic modification is used to improve fuel cell performance. Power is enhanced several fold. The development of cells with improved carbon monoxide tolerance remain areas of interest.

Bioelectrochemical Ammonia Production with Blue-Green Algae

Nitrogenase is an enzyme that catalyzes the conversion of atmospheric nitrogen (N2) to ammonia (NH3) and hydrogen (H2). The energetic input to drive this reaction is primarily from sunlight. Sunlight induces the biochemical pathways in cyanobacteria (blue-green algae) through chloroplasts, pigmented structures found in these algae. The energy from incident photons drives several respiratory and electron-transport chain reactions throughout the cells, ultimately providing the necessary reducing power (electrons) and co-factors (adenosine triphosphate, nicotinamide adenine dinucleotide, ferredoxins) to drive the reduction of nitrogen. The ammonia and hydrogen produced are consumed by the plant to support growth; thus ammonia is used commercially in the farming industry as a fertilizer. Ammonia can also be used as a fuel in several reported ways: combustion engines, pressure engines, furnaces, and fuel cells. Commercial production of ammonia relies upon the energetically and evnrionmentally taxing synthetic process called the Haber Bosch synthesis. Briefly, cracked methane provides hydrogen gas which is reacted with atmospheric nitrogen at a catalyst surface and extreme temperatures and pressures (at least 300 ATM and 700K) to produce ammonia. While an extremely energy-dependent process, it's the most efficient commercial process used today. It is estimated that approximately 1% of world energy consumption goes to synthesizing ammonia. Because nitrogenase, nitrate/nitrite reductase, and other enzymes found in cyanobacteria are metalloenzymes dependent upon redox potentials, electrochemical perturbation and control of ammonia production is possible. In the Leddy lab, we culture Anabaena variabilis, a strain of cyanobacteria known for high production of ammonia in vitro, and study them electrochemically to generate excess ammonia.

Thin Layer Sonoelectrochemistry

On irradiation with ultrasound (sonication), fluids undergo compression and rarefaction to form microscopic bubbles. On a subsequent compression cycle, bubbles collapse and tremendous temperatures and pressures are generated at the narrow interface between the fluid and void. In bulk electrochemical systems, sonication provides so much energy that electrode pitting and particle welding is common along with increases in mass transport. The extensive cavitation and turbulence also create a lot of (signal) noise. In a thin layer system, it is not necessary to sonicate to the point of cavitation. Acoustic energy is reflected within the cell and influences heterogeneous electron transfer rates while the impact on mass transport is negligible.

Electroanalytical Methods of Film Characterization

Films (e.g. polymer films, metal depositions, oxidation layers, etc.) change the way molecules diffuse or migrate. Understanding how films affect mass transport is important for many applications such as fuel cell membranes, pharmaceutical drug delivery, and battery charge/discharge life. Simulations for cyclic voltammetry at film modified electrodes are developed by finite difference methods. Experimental data can be fitted and analyzed with diagnostics created from the simulations. Films with nonuniform density profiles have unique mass transport properties. For example, films of the polymer Ficoll form a graded density film in which the film is most dense at the electrode surface and becomes linearly less dense out into solution. This gradient creates a "passive stirring" effect that approaches a steady state feed of probe to the electrode surface.

Undergraduate Metal Bipyridine Synthesis Review Paper

Fall ICRU Research Festival Video Submission

Please check out this short video created by undergraduate students.