ORR In Alkaline Media Research Articles

A template-free route to a Fe3O4–Co3O4 yolk–shell nanostructure as a noble-metal free electrocatalyst for ORR in alkaline media

This paper reported a facile template-free route to prepare hierarchical Fe3O4–Co3O4 yolk–shell nanostructures. These highly porous architectures, with a diameter of about 2 μm, were assembled from Co3O4 flower-like shells and Fe3O4 sphere core. A series of experiments with different conditions were carried out to determine the key factors in this typical solvothermal synthesis that led to the formation of the obtained yolk–shell nanostructures, and a possible growth mechanism was proposed. Sequentially, some other similar metal oxide nanostructures were also obtained in this way. Importantly, the obtained Fe3O4–Co3O4 yolk–shell nanostructures exhibit excellent electrocatalytic ORR performance. The half-wave potential of the yolk–shell nanostructures is about 5 and 80 mV positive-shifted compared to that of the independent Co3O4 and Fe3O4 nanoparticles. The current density of O2 reduction for the Fe3O4–Co3O4 yolk–shell nanostructures is also much higher than that of Co3O4 and Fe3O4 nanoparticles. The enhanced electrocatalytic performance for Fe3O4–Co3O4 yolk–shell nanostructures may make them available to be an efficient and cheap noble-metal free cathodic catalyst for PEMFCs.

Manganese Oxide/Carbon-Based Electrocatalysts for ORR in Alkaline Medium: Mechanism

not Available.

Evaluation of a sheep model of atrial fibrillation

We have revisited correlations between catalytic activity and formal potentials of MN4 catalysts for the reduction of O2 (ORR). When comparing the activities of Cr, Mn, Co and Fe MN4 complexes for ORR as a plot of (log i/n)E versus the M(III)/(II) formal potential of the catalyst (n = number of electrons involved in the ORR), two linear correlations are obtained: one for Cr, Mn and Fe complexes and another for Co complexes. Mn and Fe are 4-electron reduction catalysts and Cr and Co are 2-electron reduction catalysts for ORR in alkaline media. We show that instead of plotting the formal potential E°′ of the catalyst but the difference between this parameter and the reversible potential Erev of the corresponding catalytic reaction (O2/OH−) or (O2/HO2−), as (E°′ − Erev) and using the Co(II)/(I) formal potential for cobalt macrocyclics, instead of the Co(III)/(II) redox couple, all data points merge into one single linear correlation of slope + 0.170 V/decade. It is possible that when (E°′ − Erev) approaches zero, the maximum activity could be achieved and this is especially important for 4-electron catalysts and the linear correlation might be part of an incomplete volcano correlation.