N-Doped carbon materials are promising candidates as alternative catalysts to noble metals in promoting the oxygen reduction reaction (ORR) in fuel cells. However, methods to further reduce the ORR overpotential and improve related kinetics remain to be developed. This study reports that N-doped graphene frameworks (NGFs) synthesized from the rapid pyrolysis of solid glycine particles in the presence of sodium carbonate, display an extremely large specific surface area (1760 m(2) g(-1)) and a graphitic-N-dominant C-N configuration. The NGFs can efficiently catalyze the electrochemical reduction of molecular oxygen into water following a 4e pathway, with a low overpotential (0.98 V of onset potential vs. RHE), very high kinetic limiting current density (16.06 mA cm(-2)), and turnover frequency (121 s(-1)), much better than the commercial Pt/C catalyst.

SrRuO3 (SRO) thin films with different thickness (2–70 nm) have been grown on (001), (110), and (111) SrTiO3 substrates. The (001)-SRO films (2–8 nm) exhibited smooth flat surfaces whereas the (110)- and (111)-SRO films featured a faceted island structure. Room temperature resistivity and residual resistivity are the lowest for the (111)-SRO films (30–70 nm). Over all thicknesses, we observed enhanced magnetization in the (111)-SRO films (∼4 μB/Ru) compared with that for the (001)- and (110)-SRO films (∼2 μB/Ru and ∼3 μB/Ru, respectively), suggesting a low-spin state t2g(3↑,1↓), high-spin state t2g(3↑)eg(1↑), and mixed low- and high-spin states for the (001)-, (111)-, and (110)-SRO films, respectively. The dependence of resistivity on temperatures near TC follows a power law with exponent β = 0.312 and β = 0.363 for the (110)- and (111)-SRO films, respectively. These critical exponents are consistent with magnetic data with scaling law M = C (TC − T)β. At low temperatures, dM/dT and dρ/dT show a linear relationship in the temperature range for the Fermi liquid. These results suggest that the intrinsic electrical and magnetic transport properties are coupled.

The crystal structures and magnetic properties of the 40 nm brownmillerite SrMnO2.5 film, perovskite SrMnO3-δ film, and mixed-phase film have been systematically investigated. The features of the oxygen vacancy ordering superstructure in the brownmillerite SrMnO2.5 film are observed from HRSTEM as follows: the dark stripes with a periodicity of four (110) planes of the cubic perovskite appearing at an angle of 45° with the substrate-film interface and extra reflection spots in fast Fourier transformation patterns along the (001) plane. When annealing the brownmillerite SrMnO2.5 film under higher oxygen pressure, the top portion undergoes structure transition into perovskite SrMnO3-δ as seen in the mixed-phase film consisting of the perovskite SrMnO3-δ phase dominating at the top part and the brownmillerite SrMnO2.5 phase dominating at the bottom part. The magnetic properties and Mn valences of the brownmillerite SrMnO2.5 film indicate that this film, similar to the bulk, is antiferromagnetic with TN at 375 K. However, the strained tetragonal perovskite SrMnO3-δ film exhibits ferromagnetic behavior with Curie temperature at 75 K and a saturation magnetization of 2.5μB/Mn at 2 K. Moreover, the top perovskite SrMnO3-δ phase of the mixed-phase film also exhibits ferromagnetic behavior evidenced by the existence of the exchange bias. We propose that the ferromagnetic properties in both the perovskite SrMnO3-δ film and the top perovskite SrMnO3-δ phase in the mixed-phase film originate from Mn3+–Mn4+ double exchange coupling. However, the formation of Mn3+ differs for the two samples in that it is caused by oxygen vacancies in the former and the distribution of oxygen content across the film during annealing in the latter.

Au–LaNiO3 (Au–LNO) nanocomposite films with 3.84 at% Au were firstly fabricated by one-step chemical solution deposition (CSD), and their electrical properties were investigated.

Bilayers of La0.7Sr0.3MnO3/NiO and LaMnO3/NiO were prepared and magnetic exchange coupling investigated in these bilayers, where the Curie temperature of the ferromagnetic (FM) layer is lower than the Néel temperature of the antiferromagnetic layer. After small-field cooling, the LSMO/NiO bilayer exhibits an exchange bias with field HEB = 60 Oe, whereas the LMO/NiO sample shows weak magnetic interaction (∼22 Oe). The unconventional exchange bias in LSMO/NiO bilayer vanishes as temperature rises above 50 K. The weak magnetic interaction at the LMO/NiO interface is due to a larger Hubbard parameter value and smaller transfer integral value in the Mott insulator LMO compared with that for the FM conductor LSMO. The valence states of Mn and Ni ions across the interfaces for LSMO/NiO and LMO/NiO have been studied using X-ray photoelectron spectroscopy. We speculate that the FM interaction between Ni2+ and Mn4+ gives rise to magnetic regions that pin the ferromagnetic LSMO layer.