Cobalt-Copper-Embedded Nitrogen-Doped Carbon Nanostructures Derived from Zeolite Imidazolate Frameworks as Electrocatalysts for the Oxygen Reduction Reaction.

In recent years, researchers have focused on developing zeolite imidazolate frameworks (ZIFs) as an alternative to Pt electrocatalysts for various applications, including water splitting, lithium-air batteries, zinc-air batteries, and fuel cells. In this study, we synthesized CoCu-ZIF to be used as a precursor in the development of cathode catalysts for the oxygen reduction reaction (ORR) in fuel cells. Hydrazine played a crucial role in maintaining uniformity in the development and particle size of the ZIF-67 structures. Moreover, it facilitated the rapid formation of the ZIF-67 structures at higher temperatures. A unique pseudorhombic dodecahedral morphology was obtained at a Co/Cu molar ratio of 7:3. Among all the synthesized N-doped carbon nanostructures embedded with Co and Cu nanoparticles, CoCu@NC-750, pyrolyzed at 750 °C, showed superior ORR catalytic performance. This catalyst exhibited a notably higher half-wave potential of 0.816 V and demonstrated a clear 4-electron transfer mechanism. The overpotential of CoCu@NC-750 shifted by only 11 mV over 10,000 cyclic voltammetry cycles, whereas a 55 mV shift was observed for Pt/C. CoCu@NC-750 exhibited a ∼0.8% decrease in current density during a 12-h ORR, in contrast to the 8.3% decline shown by Pt/C. This superior catalytic activity and stability can be attributed to factors such as higher oxygen adsorption induced by the N-doped carbon layer due to the localized changes in electron density and the enhanced stability of the bimetallic core. Our findings suggest that CoCu@NC-750 is a promising alternative to Pt/C in fuel cell cathodes.

Low content Ru-incorporated Pd nanowires for bifunctional electrocatalysis.

This paper reports the facile synthesis and characterization of carbon supported Pd nanowires with low Ru contents (nRuPd/C). An anti-galvanic replacement reaction involving the reduction of Ru(iii) ions by nanoporous Pd nanowires to form nRuPd alloy nanowires was observed. A series of nRuPd/C materials with various Ru/Pd ratios were prepared by the spontaneous deposition of a Ru cluster on a Pd nanowire core using different Ru precursor concentrations (RuCl3 = 0.5, 1.0, 5.0 mM). The successful formation of low content Ru-incorporated Pd nanowires without individual Ru clusters were confirmed using physicochemical characterization. The electrocatalytic activity of the nRuPd/C for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in alkaline media was measured by RDE polarization experiments. The electrocatalytic activity varied greatly depending on the Ru content on the Pd nanowires. Among the catalysts, the prepared Pd nanowires incorporated with a very small amount of Ru (ca. 1.4 wt%) exhibited excellent electrocatalytic activity toward the ORR and HER: positive ORR/HER onset and E 1/2 potentials, higher n value, and lower Tafel slope.

Photochemical Approach for the Preparation of N-Alkyl/Aryl Substituted Fulleropyrrolidines: Photoaddition Reactions of Silyl Group Containing α-Aminonitriles with Fullerene C60.

The photochemical reactions of C60 with N-(trimethylsilyl)methyl substituted and N-alkyl/aryl substituted α-aminonitriles were explored to evaluate the scope and reaction efficiency depending on the structural nature of amine substrates. The results showed that photoreactions of C60 with trimethylsilyl group containing N-alkyl amines produced predominantly both trimethylsilyl and cyano group containing trans-pyrrolidine ring fused fulleropyrrolidines in a chemo- and stereoselective manner. Interestingly, photoreactions of C60 with N-branched alkyl substituted amines led to exclusive formation of non-silyl containing cycloadducts. In contrast to those of N-alkyl substituted α-aminonitriles, photoreactions of N-(trimethylsilyl)methyl and N-aryl substituted α-aminonitriles gave rise to the formation of both trans- and cis-isomeric fulleropyrrolidines with an inefficient and non-stereoselective manner. The feasible mechanistic pathways leading to generation of fulleropyrrolidines are 1,3-dipolar cycloaddition of the azomethine ylides, generated by either a single electron transfer (SET) (under N2-purged conditions) or H atom abstraction (under O2-purged conditions) process, to fullerene C60. The stereoselectivities of photoproducts depending on the nature of amines are likely to be associated with conformational stabilities of in situ generated azoemthine ylides.