No abstract

Fuel cells are considered as the only viable solution for long-range electromobility, but very rare and expensive platinum is currently required for catalyzing the bottleneck reaction therein: oxygen reduction. Within the search for catalysts that are not based on precious metals, cobalt corroles were uncovered to fulfill the requirements of high selectivity and low overpotential. We now report on the electropolymerization of a specifically designed catalyst, a cobalt­(III) complex of tris­(4-aminophenyl)­corrole, upon which 3D polymeric structures were obtained. Much better catalytic activity was obtained by this approach in comparison to monomeric catalyst, manifested by significantly lower overpotentials, as well as higher selectivity to the desired 4e–/4H+ pathway. The performance in an alkaline environment makes it the most active molecular catalyst for the oxygen reduction reaction reported to date.

No abstract

Owing to their unique chemistry and physical properties, metal-organic frameworks (MOFs) are an interesting class of materials which can be utilized for a wide array of applications. MOFs have been proposed to be used as catalysts for fuel cells, but their low intrinsic electronic conductivity hampered their utilization as is. In this work, we present the synthesis and application of MOF-based precious-metal-group-free (PGM-free) catalysts for oxygen reduction based on a unique metal-organic framework-carbon composite material. Benzene tricarboxylic acid-based MOFs were synthesized inside activated carbon (AC) with four different, first row transition metals: Mn, Fe, Co, and Cu. The MOFs@AC were analyzed electrochemically to measure their catalytic activity. Further physical and chemical characterization studies are performed to measure the material properties. The MOFs@AC are found to be conductive and active catalysts for the oxygen reduction reaction in an alkaline environment. Surprisingly, the Mn-MOF-based@AC exhibits the best performance with an onset potential of 0.9 V vs. RHE and the almost four-electron mechanism, as opposed to most other known PGM-free catalysts, which show Fe and Co as the most active metals.