Oxygen Reduction Behavior of Highly Porous Non-Noble Metal Catalysts Prepared by a Template-Assisted Synthesis Route

Abstract

Highly porous non-noble metal catalysts have been prepared by template-assisted synthesis, a nanocasting procedure. A mesoporous silica gel was used to prepare different oxygen reduction catalysts. The synthesis procedure consists of the following steps: impregnation of the template with different transition metal salts ͑FeCl 3 or CoCl 2 ͒, pore filling of the impregnated host material with pyrrole, polymerization of pyrrole with hydrochloric acid and subsequent carbonization in argon as well as final liberation of the catalyst material by dissolving the template framework and the transition metal in hydrofluoric acid. The obtained catalyst samples are highly porous and exhibit outstanding oxygen reduction behavior. The Brunauer, Emmett, and Teller method surface areas between 670 and 1030 m 2 /g and pore volumes ranging from 1.6 to 2.4 cm 3 /g have been observed. Onset potentials up to 0.85 V were recorded during the oxygen reduction reaction ͑ORR͒. Different parameters affecting ORR activity ͑e.g., metal source, metal concentration of host material, annealing temperature͒ have been investigated and are discussed. Corresponding non-noble metal catalysts have been characterized by X-ray diffraction measurements, elemental analysis, scanning electron microscopy, and nitrogen adsorption.

Ordered mesoporous porphyrinic carbons with very high electrocatalytic activity for the oxygen reduction reaction

“…Since Jasinski reported the electrocatalytic activity of Co-phthalocyanine for ORR in an alkaline medium7, the class of non-precious metal catalysts has been a topic of continuous interests89101112131415161718192021222324252627282930313233343536. The non-precious metal catalysts for ORR consist of naturally abundant transition metals (primarily Fe or Co), nitrogen, and carbon; such catalysts are commonly prepared by mixing the sources of each component, followed by pyrolysis in inert or reactive gas environment891011.…”

Recent progress in non‐precious metal catalysts for PEM fuel cell applications

“…The optimised materials were found to provide excellent ORR activity and promising stability capabilities investigated by half‐cell electrochemical testing methods. Although PEMFC performance was not evaluated, these templating techniques are very promising in order to produce NPMC with high active site densities, dispersed both throughout the bulk and on the surface of the catalyst particles . Moreover, with careful design and selection of the sacrificial template materials, the structure of the NPMC can be deliberately tailored in order to optimise pore structures, sizes and distributions that can further improve active site densities and provide enhanced mass transport properties when incorporated into catalyst layers.…”

A non-precious metal catalyst for oxygen reduction prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride

“…The basic steps include [8,9]: (1) transition metal ions are chelated with macrocyclic compounds to form a complex; (2) carbon black is added to adsorb the complex onto its surface; (3) the mixture is dried and heat-treated at a high temperature in an inert atmosphere. Recently, the phthalocyanine and porphyrin were also substituted by other nitrogen-containing compounds to synthesize the catalyst, such as aniline [10], tripyridyl triazine [11], pyrrole [12], triethylenetetramine [13], etc.…”