6 research outputs found
Exploring scale invariance in the expansion of a spherical unitary Fermi gas
A unitary Fermi gas in an isotropic harmonic trap is predicted to show scale
and conformal symmetry that have important consequences in its thermodynamic
and dynamical properties. By experimentally realizing an isotropic harmonic
trap, we study the expansion of a unitary Fermi gas and demonstrate its
universal expansion dynamics along different directions and at different
temperatures. We show that as a consequence of SO(2,1) symmetry, the measured
release energy is equal to that of the trapping energy. In addition, away from
resonance when scale invariance is broken, we determine the effective exponent
that relates the chemical potential and average density along the
BEC-BCS crossover, which qualitatively agrees with the mean field predictions.
This work opens the possibility of studying non-equilibrium dynamics in a
conformal invariant system in the future.Comment: 15 pages and 8 figur
Pt/Pd Decorate MOFs Derived Co-N-C Materials as High-Performance Catalysts for Oxygen Reduction Reaction
We report here, a strategy to prepare Pt/Pd nanoparticles decorated with Co-N-C materials, where Co-N-C was obtained via pyrolysis of ZIF-67 directly. As-prepared Pt/Pd/Co-N-C catalysts showed excellent ORR performance, offered with a higher limit current density (6.6 mA cm−2) and similar half-wave potential positive (E1/2 = 0.84 V) compared with commercial Pt/C. In addition to an ORR activity, it also exhibits robust durability. The current density of Pt/Pd/Co-N-C decreased by only 9% after adding methanol, and a 10% current density loss was obtained after continuous testing at 36,000 s
Pt/Pd Decorate MOFs Derived Co-N-C Materials as High-Performance Catalysts for Oxygen Reduction Reaction
We report here, a strategy to prepare Pt/Pd nanoparticles decorated with Co-N-C materials, where Co-N-C was obtained via pyrolysis of ZIF-67 directly. As-prepared Pt/Pd/Co-N-C catalysts showed excellent ORR performance, offered with a higher limit current density (6.6 mA cm−2) and similar half-wave potential positive (E1/2 = 0.84 V) compared with commercial Pt/C. In addition to an ORR activity, it also exhibits robust durability. The current density of Pt/Pd/Co-N-C decreased by only 9% after adding methanol, and a 10% current density loss was obtained after continuous testing at 36,000 s