Vijay Sethuraman

University of South Carolina | USC · Department of Chemical Engineering

In this work, we report direct/ in situ measurements of stress and potential evolution during self-discharge of a fully lithiated silicon electrode. Parasitic reactions, typically attributed to the formation of the solid-electrolyte-interphase (SEI) layer on the surface of the silicon electrode, cause the self-discharge leading to the loss of cycla...

In situ electrochemical cells were assembled with an amorphous germanium (a-Ge) film as working electrode and sodium foil as reference and counter electrode. The stresses generated in a-Ge electrodes due to electrochemical reaction with sodium were measured in real-time during the galvanostatic cycling. A specially designed patterned a-Ge electrode...

Electric field-induced “etching” of Cr film is a tip-based patterning technique that is used to create micro- and nano-sized trenches in the film under ambient conditions. The experimental data obtained in this study reveals that the etching of Cr occurs via the formation of water-soluble CrO3, which spontaneously forms at the cathode tip when a la...

In situ electrochemical cells were assembled with an amorphous germanium (a-Ge) film as working electrode and sodium foil as reference and counter electrode. The stresses generated in a-Ge electrodes due to electrochemical reaction with sodium were measured in real-time during the galvanostatic cycling. A specially designed patterned a-Ge electrode...

Automotive battery manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost and active material volume change is one of the more complex aspects that needs to be considered during this process. To improve the balance between cost, stability, performance,...

Vortex Induced Vibrations (VIVs), a phenomenon where the fluid flow causes oscillations against an object called a bluff body by vortex shedding, have been studied as a source of renewable energy. However, few studies have focused on the use of VIVs for maritime propulsion. In this investigation, a novel VIV based piezoelectric generator and rechar...

Herein, in-situ reduction of bismuth and graphene oxide was performed by a solvothermal method under a nitrogen atmosphere, and the resulting Bi on RGO nanocomposites were used as an anode material for Mg-ion batteries. The nanocomposite of 60% Bi:40% RGO is a beneficial anode material, delivering a discharge capacity as high as 413 and 372 mAh per...

A one dimensional (1-D), isothermal model for a direct methanol fuel cell (DMFC) is presented. This model accounts for the kinetics of the multi-step methanol oxidation reaction at the anode. Diffusion and crossover of methanol are modeled and the mixed potential of the oxygen cathode due to methanol crossover is included. Kinetic and diffusional p...

Understanding the role of elastic strain in modifying catalytic reaction rates is crucial for catalyst design, but experimentally, this effect is often coupled with a ligand effect. To isolate the strain effect, we have investigated the influence of externally applied elastic strain on the catalytic activity of metal films towards the hydrogen evol...

The effect of silicone on the catalytic activity of Pt for oxygen reduction and hydrogen adsorption was studied using di-phenyl siloxane as a source compound at a rotating disc electrode (RDE). Di-phenyl siloxane did not affect the catalytic activity of Pt when it was injected into the electrolyte. However, it blocked the oxygen reduction reaction...

Here, we study the role of stress state and stress gradient in whisker growth in Sn coatings electrodeposited on brass. The bulk stress in Sn coatings was measured using a laser-optics based curvature setup, whereas glancing angle X-ray diffraction was employed to quantify the surface stress; this also allowed studying role of out-of-plane stress g...

Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane (PEM) fuel cell anode and cathode were estimated as a function of humidity and temperature by studying the oxygen reduction reaction (ORR) on a rotating ring disc electrode (RRDE). Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the dis...

The role of stress state and stress gradient in whisker growth in Sn coatings electrodeposited on brass is examined. The bulk stress in Sn coatings was measured using a laser-optics-based curvature setup, whereas glancing angle x-ray diffraction was employed to quantify the stress near the surface; this also allowed studying the role of the out-of-...

In-situ reduction of bismuth and graphene oxide (Bi/RGO) nanocomposites have been prepared by solvothermal method under N2 atmosphere as an anode material for Mg-ion batteries. The nanocomposite of 60% Bi : 40% RGO is the beneficial anode material, delivering discharge capacity as high as 413 and 372 mAh g-1 at a specific current of 39 mA g-1 in th...

Solid oxide fuel cells (SOFCs) are considered as important green energy devices for the 21 st century due to its high chemical to electrical energy conversion efficiency, modular design and fuel flexibility. However, the widespread commercialization of SOFCs has not been realized due to its cost associated with cell fabrication, electrode/ electrol...

Understanding the role of elastic strain in modifying catalytic reaction rates is crucial for catalyst design, but experimentally, this effect is often coupled with a ligand effect. To isolate the strain effect, we have investigated the influence of externally applied elastic strain on the catalytic activity of metal films in the hydrogen evolution...

An in situ study of stress evolution and mechanical behavior of germanium as a lithium-ion battery electrode material is presented. Thin films of germanium are cycled in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1M LiPF 6 in ethylene carbonate, diethyl carbonate, dimethyl carbonate solution (1:1:1, wt%)...

An in situ study of stress evolution and mechanical behavior of germanium as a lithium-ion battery electrode material is presented. Thin films of germanium are cycled in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1M LiPF6 in ethylene carbonate, diethyl carbonate, dimethyl carbonate solution (1:1:1, wt%) a...

Composite cathode coatings made of a high energy density layered oxide (Li1.2Ni0.15Mn0.55Co0.1O2, theoretical capacity ∼377 mAh-g−1), polyvinylidene fluoride (PVdF) binder, and electron-conduction additives, were bonded to an elastic substrate. An electrochemical cell, built by pairing the cathode with a capacity-matched graphite anode, was electro...

The effect of elastic strain on catalytic activity of platinum (Pt) toward oxygen reduction reaction (ORR) is investigated through dealloyed Pt-Cu thin films; stress evolution in the dealloyed layer and the mass of the Cu removed are measured in real-time during electrochemical dealloying of (111)-textured thin-film PtCu (1:1, atomic ratio) electro...

The well-known hydrogen evolution reaction (HER) volcano plot describes the relationship between H binding energy and the corresponding hydrogen evolution catalytic activity, which depends on the species of metal. Under CO2/CO reduction conditions or in cases where CO impurities enter electrodes, the catalyst may exist under a high coverage of coad...

Structural changes in amorphous LixSi during the initial lithiation of single crystal Si to amorphous LixSi were investigated as a function of Li flux and total charge using solid-state Li-7 nuclear magnetic resonance (NMR) spectroscopy. Single crystal (100) Si wafers were used as a model system in this study, as the Li flux could be precisely cont...

A combination of experimental measurements and numerical simulations are used to characterize the mechanical and electrochemical response of thin film amorphous Si electrodes during cyclic lithiation. Parameters extracted from the experiment include the variation of elastic modulus and the flow stress as functions of Li concentration; the strain ra...

An in situ study of deformation, fracture, and fatigue behavior of silicon as a lithium-ion battery electrode material is presented. Thin films (100-200 nm) of silicon are cycled in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1M lithium hexafluorophosphate in ethylene carbonate, diethylene carbonate, dimet...

The electrochemical oxidation of carbon monoxide adsorbed (COad) on platinum-on-carbon electrodes was studied via a methodology in which pre-adsorbed CO was partially oxidized by applying potentiostatic pulses for certain durations. The residual COad was analyzed using stripping voltammetry that involved the deconvolution of COad oxidation peaks of...

Five parameters of a model of a polymer electrolyte membrane fuel cell cathode (the porosity of the gas diffusion layer, the porosity of the catalyst layer, the exchange current density of the oxygen reduction reaction, the effective ionic conductivity of the electrolyte, and the ratio of the effective diffusion coefficient of oxygen in a flooded s...

We report real-time average stress measurements on composite silicon electrodes made with two different binders [Carboxymethyl cellulose (CMC), and polyvinylidene fluoride (PVDF)] during electrochemical lithiation and delithiation. During galvanostatic lithiation at very slow rates, the stress in a CMC-based electrode becomes compressive and increa...

Recently, much emphasis has been placed on reducing the use of fossil fuels and the emission of greenhouse gases. To address these two interrelated issues, newer governmental regulations demand a sequential increase in energy-efficiency standards from auto manufacturers over the next two decades. Electrochemical energy-storage and energy-conversion...

Charge lost per unit surface area of a silicon electrode due to the formation of solid-electrolyte-interphase (SEI) layer during initial lithiation was quantified, and the species that constitute this layer were identified. Coin cells made with Si thin-film electrodes were subjected to a combination of galvanostatic and potentiostatic lithiation an...

A one-dimensional, isothermal model for a direct methanol fuel cell (DMFC) is presented. This model accounts for the kinetics of the multi-step methanol oxidation reaction at the anode. Diffusion and crossover of methanol are modeled and the mixed potential of the oxygen cathode due to methanol crossover is included. Kinetic and diffusional paramet...

Real-time stress evolution in a graphite-based lithium-ion battery negative electrode during electrolyte wetting and electrochemical cycling is measured through wafer-curvature method. Upon electrolyte addition, the composite electrode develops compressive stress of 1–2 MPa due to binder swelling. During electrochemical intercalation, the compressi...

Analysis of lithiation and delithiation kinetics in pulse-laser-deposited crystalline thin-film silicon (Si) electrodes is presented. Data from open-circuit relaxation experiments are used in conjunction with a model based on Tafel kinetics and double-layer capacitance to estimate the apparent transfer coefficients ({\alpha}a, {\alpha}c), and excha...

It is shown that continuously occurring electrolyte-reduction reaction on freshly-exposed electrode surfaces during lithiation/delithiation cycles causes the lowering of cycling efficiency, and hence, capacity fade in well-cycled silicon anodes in lithium-ion batteries. Using galvanostatic lithiation/delithiation data from multiple cycles on a Li/S...

A Devanathan-Stachurski type diffusion cell made from a fuel cell assembly is designed to evaluate the gas transport properties of a proton exchange membrane as a function of cell temperature and gas pressure. Data obtained on this cell using the electrochemical monitoring technique (EMT) is used to estimate solubility and diffusion coefficient of...

We report on the origin of the surface structural disordering in graphite anodes induced by lithium intercalation and deintercalation processes. Average Raman spectra of graphitic anodes reveal that cycling at potentials that correspond to low lithium concentrations in LixC (0 \leq x < 0.16) is responsible for most of the structural damage observed...

We report in situ measurement of biaxial moduli of a Si thin-film electrode as a function of its lithium concentration. During lithiation, biaxial compressive stress is induced in the Si film and it undergoes plastic flow. At any state-of-charge (SOC), a relatively small delithiation-relithiation sequence unloads and reloads the film elastically. F...

Graphitic carbon is currently considered the state-of-the-art material for the negative electrode in lithium-ion cells, mainly due to its high reversibility and low operating potential. However, carbon anodes exhibit mediocre charge/discharge rate performance, which contributes to severe transport-induced surface-structural damage upon prolonged cy...

The extent of irreversible deactivation of Pt towards hydrogen oxidation reaction (HOR) due to sulfur adsorption and subsequent electrochemical oxidation is quantified in a functional PEM fuel cell. At 70 {\deg}C, sequential hydrogen sulfide (H2S) exposure and electrochemical oxidation experiments indicate that as much as 6% of total Pt sites are d...

We report in situ measurements of stress evolution in a silicon thin-film electrode during electrochemical lithiation and delithiation by using the Multi-beam Optical Sensor (MOS) technique. Upon lithiation, due to substrate constraint, the silicon electrode initially undergoes elastic deformation, resulting in rapid rise of compressive stress. The...

Cycling efficiency and rate capability of porous copper-coated, amorphous silicon thin-film negative electrodes are compared to equivalent silicon thin-film electrodes in lithium-ion batteries. The presence of a copper layer coated on the active material plays a beneficial role in increasing the cycling efficiency and the rate capability of silicon...

An analysis of the dependence of electric potential on the state of stress of a lithiated-silicon electrode is presented. Based on the Larch\'e and Cahn chemical potential for a solid solution, a thermodynamic argument is made for the existence of the stress-potential coupling in lithiated-silicon; based on the known properties of the material, the...

Crystalline to amorphous phase transformation during initial lithiation in (100) Si wafers is studied in an electrochemical cell with Li metal as the counter and reference electrode. During initial lithiation, a moving phase boundary advances into the wafer starting from the surface facing the lithium electrode, transforming crystalline Si into amo...

We formulate the continuum field equations and constitutive equations that govern deformation, stress, and electric current flow in a Li-ion half-cell. The model considers mass transport through the system, deformation and stress in the anode and cathode, electrostatic fields, as well as the electrochemical reactions at the electrode/electrolyte in...

Electrochimica Acta j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e l e c t a c t a a b s t r a c t The role of catalyst stability on the adverse effects of hydrogen peroxide (H 2 O 2) formation rates in a proton exchange membrane fuel cell (PEMFC) is investigated for Pt, Pt binary (PtX, X = Co, Ru, Rh, V, Ni) and...

A simple procedure to quantify the rates of carbon monoxide (CO) desorption from, and simultaneous rearrangement on, supported platinum fuel cell electrode (Pt on Vulcan XC-72R) is reported. The surface coverage of CO on Pt electrode in equilibrium with bulk CO was measured from the anodic peaks in the CO stripping voltammogram. The decline in thes...

The field of electrochemical engineering, especially the design and analysis of electrochemical systems, has progressed greatly due to the work of Professor John Newman at the University of California, Berkeley. We present the academic family tree of Professor John Newman comprising his students and their students, and a list of theses and disserta...

The effect of humidity on the chemical stability of two types of membranes [i.e., perfluorosulfonic acid type (PFSA, Nafion 112) and biphenyl sulfone hydrocarbon type, (BPSH-35)] was studied by subjecting the membrane electrode assemblies (MEAs) to open-circuit voltage (OCV) decay and potential cycling tests at elevated temperatures and low inlet-g...

Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane fuel cell (PEMFC) anode and cathode were estimated as a function of humidity and temperature by studying the oxygen reduction reaction (ORR) on a rotating ring disk electrode. Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and...

The effect of silicone on the catalytic activity of Pt for oxygen reduction and hydrogen adsorption was studied using diphenyl siloxane as a source compound at a rotating disk electrode (RDE). Diphenyl siloxane did not affect the catalytic activity of Pt when it was injected into the electrolyte. However, it blocked the oxygen reduction reaction wh...

A model and an analytical solution for the model are presented for the resistance of the polymer electrolyte membrane of a H2/O2 fuel cell. The solution includes the effect of the humidity of the inlet gases and the gas pressure at the anode and the cathode on the membrane resistance. The accuracy of the solution is verified by comparison with expe...

A concise mechanism for the poisoning kinetics of hydrogen sulfide (H 2 S) on composite solid polymer electrolyte Pt (SPE-Pt) electrode is presented. The simplified version of the mechanism is validated experimentally by charge balances and theoretically by a model, which predicts the oxidation current as a function of the applied potential. H 2 S...

Typescript. Thesis (Ph. D.)--University of South Carolina, 2006. Includes bibliographical references (leaves 163-172).

Five parameters of a model of a polymer electrolyte membrane fuel cell (PEMFC) cathode (the volume fraction of gas pores in the gas diffusion layer, the volume fraction of gas pores in the catalyst layer, the exchange current density of the oxygen reduction reaction, the effective ionic conductivity of the electrolyte, and the ratio of the effectiv...

ne quickly realizes that a polymer electrolyte membrane fuel cell (PEMFC) unit powered by hydrogen or methanol is more than just a stack of cells. Rather, it is a tightly integrated system of pumps, valves, flow meters, sensors, and heat exchangers that must work reliably for thousands of hours. This requires the expertise of a wide range of sci-en...

One quickly realizes that a polymer electrolyte membrane fuel cell (PEMFC) unit powered by hydrogen or methanol is more than just a stack of cells. Rather, it is a tightly integrated system of pumps, valves, flow meters, sensors, and heat exchangers that must work reliably for thousands of hours. This requires the expertise of a wide range of scien...

Performance of a Direct Methanol Fuel Cell (DMFC) was measured and characterized. The measurements were performed on a Pt anode (5mg Pt/cm 2 loading) at 60 °C and at three different feed concentrations. Crossover was monitored as a function of the current density using gas chromatography (GC). The performance of a DMFC was characterized using a mat...