Serguei Lvov

Composite Proton Conductive Membranes for Elevated Temperature and Reduced Relative Humidity PEMFC

Creation of new membrane materials for proton exchange membrane (PEM) fuel cells operating at elevated temperature and significantly reduced relative humidity (RH) is one of the major challenges in the implementation of the fuel cell technology. High-temperature PEMs are desirable for transportation applications as well as for stationary applications. Our approach is the development of new membrane materials using an inorganic proton conductor along with a proton conductive polymer (Nafion in this study). The inorganic material provide water-rich surfaces inside the membranes and allows holding on to water more tightly than in the ionomer and maintaining membrane conductivity at higher temperature and low RH. Inorganic proton conductors of different structural types with different functional groups were synthesized and characterized with respect to surface area, particle morphology, and conductivity. Composite membranes with the following inorganic additives were prepared: SiO2-SO3H, SBA-15, MCM-41, S-ZrO2, and phosphosilicate gels with different P:Si molar ratios. Three different techniques were used for fabricating the composite membranes:

Experimental System for Studying Interfacial Electrochemistry at Temperatures Above 300oC

The boiler water typically has very low concentrations of ionic species and the actual corrosion rates are relatively low. The traditional mass loss corrosion studies would require a substantial experimental time. We developed an approach using a number of electrochemical techniques designed for high temperature (HT) surface electrochemistry studies that are able to provide in-situ information on instantaneous electrochemical reaction rates at any stage of the process.

Proton Conductive Inorganics for Composite Membranes in PEM Fuel Cells

The main objective of this study is to synthesize new membrane materials in which inorganic proton conductors are deposited within a functionalized and cross-linkable Teflon-type polymer. These new composite membranes are aimed to efficiently conduct protons at temperatures above 100 oC and relative humidity (RH) down to 25% in proton exchange membrane (PEM) fuel cells. To effectively choose inorganic proton conductors, the conductivity studies of different materials are performed in our lab. An experimental system was developed and Gamry Electrochemical Impedance Spectroscopy (EIS) was applied to measure the proton conductivity of inorganic materials. Alpha zirconium phosphate was used as a standard to check the accuracy of the present experimental approach. The conductivity of the solid acid sulfated zirconia (S-ZrO2) was studied. The proton transport mechanisms in inorganic proton conductors were discussed.

Study of the Electrochemical Step of Novel Active Metal Alloy Thermochemical Cycles for Hydrogen Production

Alternative thermochemical cycles are considered promising technological solutions for hydrogen production and, in the context of the sustainable energy concept, can become a crucial part of industrial infrastructure. The medium temperature thermochemical cycles, which occur at temperatures below 600°C, are especially attractive because these conditions create an opportunity to combine the cycles with Gen IV reactor types (e.g., Na-cooled reactor, SCWR, or HTGR). The primary challenge in designing these cycles is to match the chemistry and energetics for achieving the highest efficiency. Active metal alloy thermochemical cycles offer the possibility of simpler process design and lower operation temperatures and, therefore, the possibility of lower capital costs. An example of these active metal alloy thermochemical cycles is the K-Bi cycle, which is particularly attractive due to simplicity and possibility to implement the process in a single-reactor setup. The K-Bi cycle consists of a thermochemical reaction (1) and an electrochemical reaction (2):

Surface and Electrochemical Behavior of HSLA Steel in Supercritical CO2-H2O Environment

General corrosion was observed on high strength low alloy carbon steel after electrochemical impedance spectroscopy experiments (EIS) performed in H{sub 2}O saturated with CO{sub 2} at 50 C and 15.2 MPa. However, general and localized were observed on the same material surfaces after the EIS experiments performed in supercritical CO{sub 2} containing approximately 6100 ppmv H{sub 2}O at 50 C and 15.2 MPa. The general corrosion areas were uniformly covered by the FeCO{sub 3}-like phase identified by X-ray diffraction (XRD). In the area of localized corrosion, XRD also revealed FeCO{sub 3}-rich islands embedded in {alpha}-iron. The energy dispersive X-ray (EDX) analysis revealed high concentrations of iron, carbon, and oxygen in the area affected by general corrosion and in the islands formed in the area of localized corrosion. The real and imaginary impedances were lower in H{sub 2}O saturated with CO{sub 2} than those in the supercritical CO{sub 2} containing the aqueous phase indicating faster corrosion kinetics in the former.

Interfacial Chemistry of Hydrothermal Deposition of Zirconia on Metal Substrates

Intergranular stress corrosion cracking (IGSCC) can be hazardously destructive to sensitized stainless steel components of boiling water reactors (BWRs). Several methods have been developed to mitigate IGSCC. One of the most promising is the application of dielectric coatings to stainless steel surface. It is based on an assumption that a dielectric coating will inhibit the redox reactions and corrosion process on the surface. Protective Zirconia (ZrO2 ) coating on stainless steel surface was produced using different techniques, but many of them are difficult to implement in BWRs.