To evaluate the self-regeneration feasibility of exsolved Co–Fe nanoparticles on the La0.3Sr0.7Cr0.3Fe0.6Co0.1O3−δ perovskite at intermediate operation temperature (700 °C), the evolution of surface morphology and particle phases during a redox process has been determined by scanning and transmission electron microscopy. Unlike the complete reincorporation of the exsolved metals back to the perovskite lattice at 800 °C during the reoxidation process, the transition-metal oxide remains on the surface as an intermediate phase because of a sluggish reincorporation rate at 700 °C. Although the transition-metal oxide particles grow and coarsen quickly in an oxidizing atmosphere, the nanoparticles could still be formed by a disintegration of the reduced spinel oxide in a reducing atmosphere. The hemispherical-like shape of the nanoparticles can be achieved by minimizing metallic surface energy and maintaining the strong metal–oxide interaction. The redispersion of Co–Fe nanoparticles completes the self-regeneration process at 700 °C. The exsolved nanoparticle size distribution is strongly affected by temperature but not by a redox process, which improves performance stability and reactivation at the relatively lower temperature during long-term operation.

Metal nanoparticles exsolved from perovskite oxides have created great interest as anode materials in solid oxide fuel cells (SOFC) due to their high catalytic activity and regenerative capability. However, the self-regeneration process generally occurs at relatively high temperatures (>800 °C), which might limit their practical application. Here, we present a perovskite anode material, La0.3Sr0.7Cr0.3Fe0.6Co0.1O3−δ, which allows Co–Fe nanoparticles exsolved on the oxide surface at intermediate operation temperatures (700 °C). The phase stability of the perovskite oxide and the reversibility of the exsolved alloy were carefully examined by the phase characterization and the nanoparticle morphology observation during the redox process. The electrochemical performance was evaluated by an electrolyte-supported single cell with hydrogen and propane fuels. The Co–Fe nanocatalysts enhance the maximum power density of the La0.3Sr0.7Cr0.3Fe0.6Co0.1O3−δ–Gd0.2Ce0.8O1.9 (GDC) composite anode more than 75% in comparison to that of the cobalt-free La0.3Sr0.7Cr0.3Fe0.7O3−δ–GDC composite anode with hydrogen. The self-regeneratable anode drives off carbon deposition with hydrocarbon fuels and facilitates catalytic reactivation by the redox cycles without requiring a higher-temperature process. Additionally, the dispersed Co–Fe nanoparticles with a random distribution and slow particle growth rate ensure long-term performance. The single-cell SOFC evaluation demonstrates that La0.3Sr0.7Cr0.3Fe0.6Co0.1O3−δ with Co–Fe nanoparticles exhibits acceptable H2S tolerance, excellent redox reversibility, and stable long-term performance for more than 200 h with H2 and over 800 h with propane at 700 °C.

The mechanism and kinetics for the gas-phase hydrolysis of N(2)O(4) isomers have been investigated at the CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory in conjunction with statistical rate constant calculations. Calculated results show that the contribution from the commonly assumed redox reaction of sym-N(2)O(4) to the homogeneous gas-phase hydrolysis of NO(2) can be unequivocally ruled out due to the high barrier (37.6 kcal/mol) involved; instead, t-ONONO(2) directly formed by the association of 2NO(2), was found to play the key role in the hydrolysis process. The kinetics for the hydrolysis reaction, 2NO(2) + H(2)O ↔ HONO + HNO(3) (A) can be quatitatively interpreted by the two step mechanism: 2NO(2) → t-ONONO(2), t-ONONO(2) + H(2)O → HONO + HNO(3). The predicted total forward and reverse rate constants for reaction (A), k(tf) = 5.36 × 10(-50)T(3.95) exp(1825/T) cm(6) molecule(-2) s(-1) and k(tr) = 3.31 × 10(-19)T(2.478) exp(-3199/T) cm(3) molecule(-1) s(-1), respectively, in the temperature range 200-2500 K, are in good agreement with the available experimental data.

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Lithium-sulfur batteries are among the most promising low-cost, high-energy-density storage devices. However, the inability to host a sufficient amount of sulfur in the cathode while maintaining good electrochemical stability under a lean electrolyte condition has limited the progress. The main cause of these challenges is the sensitivity of the sulfur cathode to the cell-design parameters (i.e., the amount of sulfur and electrolyte) and the experimental testing conditions (i.e., cycling rates and analysis duration). We present here a hot-pressing method that effectively encapsulates a high amount of sulfur in the cathode within only 5 s, resulting in high sulfur loading and content of, respectively, 10 mg cm -2 and 65 wt.%. The hot-pressed sulfur (HPS) cathodes exhibit superior dynamic and static electrochemical performance under a broad cycling-rate (C/20 -1C rates) and low electrolyte/sulfur ratio (6 μL mg -1 ) conditions. The dynamic cell stability is demonstrated by high gravimetric and areal capacities of, respectively, 415 -730 mAh g -1 and 7 -12 mAh cm -2 at C/20 -1C rates with a high capacity retention of over 70% after 200 cycles. The static cell stability is demonstrated by excellent shelf-life with low self-discharge and stable cycle life on storing for over one year.