For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl3·6H2O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the prepared Ru-N-C and Ru-C catalysts via scanning transmission electron microscopy, in conjunction with energy dispersive X-ray spectroscopy, indicated the formation of hollow nanocomposites in which the average sizes of the Ru nanoparticles were 1.3 nm and 5.1 nm, respectively. Compared to Ru-C, the Ru-N-C nanocomposites not only proved to be highly active for ammonia dehydrogenation, giving rise to a NH3 conversion of >99% at 550 °C, but also exhibited high durability. X-ray photoelectron spectroscopy revealed that the Ru active sites in Ru-N-C were electronically perturbed by the incorporated nitrogen atoms, which increased the Ru electron density and ultimately enhanced the catalyst activity.
A rechargeable
aluminum-ion battery based on chloroaluminate electrolytes
has received intense attention due to the high abundance and chemical
stability of aluminum. However, the fundamental intercalation processes
and dynamics in these battery systems remain unresolved. Here, the
energetics and dynamics of chloroaluminate ion intercalation in atomically
thin single crystal graphite are investigated by fabricating mesoscopic
devices for charge transport and operando optical
microscopy. These mesoscopic measurements are compared to the high-performance
rechargeable Al-based battery consisting of a few-layer graphene–multiwall
carbon nanotube composite cathode. These composites exhibit a 60%
capacity enhancement over pyrolytic graphite, while an ∼3-fold
improvement in overall ion diffusivity is also obtained exhibiting
∼1% of those in atomically thin single crystals. Our results
thus establish the distinction between intrinsic and ensemble electrochemical
behavior in Al-based batteries and show that engineering ion transport
in these devices can yet lead to vast improvements in battery performance.
Solid oxide fuel cells (SOFCs) are promising sustainable energy systems due to their high energy conversion efficiency and low pollutant emission rate. However, the high operating temperature induces poor durability of the systems. Therefore, it is crucial to improve the oxygen reduction reaction (ORR) activity of the cathode material to lower the operating temperature. Recently, a double-layered perovskite material (AA′B 2 O 5+δ ), especially PrBaCo 1.6 Fe 0.4 O 5+δ (PBCF), has received significant attention due to its high ORR activity. Herein, we report an A-site-tailored PBCF cathode material to enhance the ORR activity by employing a dopant that can increase oxygen vacancies in the structure. Since the oxygen vacancy is known as the charge carrier for the oxygen ion in oxide materials, increasing the oxygen vacancy concentration can improve the electrochemical performances of the cathode material at a lower operating temperature range (under 600 °C). Nd was employed as a dopant at the A-site due to its similarity in size to Pr and the lower valance state, which can increase the oxygen vacancy concentration in the structure. The cathode material with 20% Nd in the A-site of PBCF showed the highest I−V−P performance and lowest activation energy for the oxygen reduction reaction. As a result, our designed material showed a high peak power density of 1.34 W/cm 2 at 600 °C, which is 109% higher than that of PBCF.
Among the various Pd1Nix alloys (x = 0.33, 1 and 3) supported on nitrogen-doped carbon, Pd1Ni1/N–C has the highest activity for formic acid (HCO2H, FA) dehydrogenation as a result of synergistic interactions between Pd and Ni atoms.
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