Hard carbon possesses the ability to store Li, Na, and K ions between stacked sp 2 carbon layers and voids (micropores). We have explored hard carbon as a candidate for negative electrode materials for Li-ion, Na-ion, and K-ion batteries. Hard carbon samples have been prepared by carbonizing sucrose at different heat treatment temperatures (HTTs) in the range of 700−2000 °C to make them structurally suitable for reversible Li, Na, and K insertion. Structures and particle morphology of the hard carbon samples synthesized at different HTTs were systematically characterized using X-ray diffraction, small-angle X-ray scattering, pair distribution function analysis, electron microscopy, Raman spectroscopy, and electron spin resonance spectroscopy. All these characterizations of hard carbon samples have revealed advanced ordering of carbons and reduction of carbon defects with increasing HTT. Thus, the average stacked carbon interlayer distance decreases, the number of the stacking layers increases, the layered domains grow in the in-plane direction, and interstitial voids enlarge. Electrochemical properties of the hard carbons were examined in nonaqueous Li, Na, and K cells. Potential profiles and reversible capacities upon galvanostatic charge/discharge processes in nonaqueous cells are significantly different depending on HTTs and different alkali metal ions. On the basis of these findings, strategies to design high-capacity hard carbon negative electrodes for high-energy-density Li-ion, Na-ion, and K-ion batteries are discussed.

The U.S. Department of Energy (DOE)-National Energy Technology Laboratory (NETL) in Morgantown, WV has developed the hybrid performance (HyPer) project in which a solid oxide fuel cell (SOFC) one-dimensional (1D), real-time operating model is coupled to a gas turbine hardware system by utilizing hardware-in-the-loop simulation. To assess the long-term stability of the SOFC part of the system, electrochemical degradation due to operating conditions such as current density and fuel utilization have been incorporated into the SOFC model and successfully recreated in real time. The mathematical expression for degradation rate was obtained through the analysis of empirical voltage versus time plots for different current densities and fuel utilizations.

Development of electrocatalysts is important for reducing the voltage loss due to the oxygen evolution reaction (OER) in metal-air batteries and water electrolyzers. In the present work, the electrocatalytic activity towards oxygen evolution for a series of lanthanum-ruthenium compounds has been investigated by steady-state current-potential measurements in alkaline media to understand the effect of structure, valence state of the transition metal ion, and the role of surface adsorbed hydroxyl species. Compounds of the perovskite family, LaRuO 3 , La 3.5 Ru 4 O 13 , and La 2 RuO 5, were prepared by the Pechini process and calcined at different temperatures to obtain the desired phases. X-ray photoelectron spectroscopy of LaRuO 3 and La 2 RuO 5 showed shifts of the Ru-3d peaks towards higher binding energies indicative of a highly oxidized surface with possibly high surface hydroxylation. The electrochemical activity of the compounds at 0.8 V vs. NHE was in the order of 10-6 A/cm 2 and the mass specific activity was about 80 mA/g. Tafel slopes were in the vicinity of 60 mV/decade for LaRuO 3 (orthorhombic) and La 3.5 Ru 4 O 13 (orthorhombic), and about 80 mV/decade for La 2 RuO 5 (monoclinic). In addition FT-IR results indicate high surface coverage by hydroxide species. The reaction order with respect to OHions was found to be lower than unity. It is possible that strong interaction of hydroxide groups with ruthenium at the surface of the electrode makes it difficult to dissociate the Ru-OH bond and prevent further interaction with dissolved OHeven at high overpotentials.

The effect due to systematic substitution of cobalt by iron in La 0.6 Ca 0.4 CoO 3 perovskites on the oxygen evolution reaction (OER) in alkaline media has been investigated. These compounds were synthesized by a facile glycine-nitrate synthesis and the phase formation was confirmed by X-ray and neutron powder diffraction analysis. The apparent OER activity was evaluated by quasisteady state current measurements in alkaline media using a traditional three-electrode system. X-ray photoelectron spectroscopy shows an increase in Fe substitution causes an increase in the surface concentration of various Co oxidation states. A Tafel slope in the vicinity of 60 mV/decade and electrochemical reaction order for OH − near unity were found for the unsubstituted compounds. A decrease in the Tafel slope to 49 mV/decade was observed when iron is incorporated in high amounts in the perovskite structure. The area specific current density showed dependence on the Fe fraction; however, the dependence of specific current density with Fe fraction is not linear. We believe that the iron incorporation in the La 0.6 Ca 0.4 CoO 3 perovskites decreases the electron transfer barrier and facilitates the formation of cobalt-hydroxides. Among the goals of modern renewable energy systems is to convert the available resources into clean forms of stored energy to alleviate the crisis of fossil fuel exhaustion and oil dependence for energy production. New battery technologies could be the key to the development of a cost-efficient renewable energy sources. Batteries are important because they allow us a method to store electric power for redistribution during the time when it is not readily available. Recently, there has been a great demand for high energy density storage devices such as metal-air batteries for stationary and electric vehicle applications.1,2 In order to develop high energy density rechargeable metal-air batteries, there is a critical need to design bifunctional oxygen electrodes capable of meeting the following essential requirements i) reduce oxygen from the atmosphere during discharging, ii) effectively dissociate the discharged oxygen products, e.g., the OER, during charging, iii) utilize low overpotential for both processes. The OER is the primary anodic process in water electrolyzers and metal-air batteries and is the main cause for energy losses and low efficiencies in these technologies due to the high overpotential required to achieve a suitable performance for functional applications.3,4 The best performing materials are associated with oxides containing noble transition metal ions such as osmium, 5 ruthenium, 6-9 iridium, and platinum-gold mixtures. 10 The increased cost of these electrocatalysts due to their scarcity in the Earth's crust makes them impractical for commercial applications. 11Therefore, efforts are dedicated toward the development of inexpensive catalytic materials for the OER as well as to understand their structural relationship with respect to the OER mechanism.Several ternary transition metal per...

The adoption of solid oxide fuel cell (SOFC) technology in power generation has been limited, in no small part, by material degradation issues affecting the stack lifetime, and hence, the economic viability. A numeric study was conducted to determine if the life of an SOFC could be extended when integrated with a recuperated gas turbine system. Dynamic modeling tools developed at the National Energy Technology Laboratory (NETL) for real-time applications were applied to evaluate life to failure for both a standalone SOFC and a hybrid SOFC gas turbine. These models were modified using empirical relations to experimental degradation data to incorporate degradation as a function of current density and fuel utilization. For the control strategy of shifting power to the turbine as fuel cell voltage degrades, the SOFC life could be extended dramatically, significantly impacting the economic potential of the technology.