Increasing the site density of non-precious metal catalysts in fuel cell electrodes

• High site density ORR catalyst matrix was electropolymerized.
• New synthetic path to from non-precious metal catalysts for oxygen reduction.
• This catalyst was studied using electrochemical techniques.
• This system may serve as a self standing catalytic layer in fuel cell electrodes.

Development of new non-precious metal based catalysts for fuel cells is crucial for the viability of the technology. This class of catalysts has relatively low turnover frequencies for oxygen reduction reaction (ORR) when compared to platinum. One way to compensate for it is to increase the catalyst site density. In this work, a model system for a high site density catalytic layer for polymer electrolyte fuel cells was synthesized and characterized. Dipyrromethane was electropolymerized on glassy carbon and glass/ITO electrodes to form a ligand matrix of up to 200 nm in thickness, to which, cobalt was introduced during the electropolymerization process. Thin polymeric sheets were observed after the electrochemical synthesis and the cobalt density in the matrix was found to be 9.84 × 1021 cobalt atoms cm−3. ORR activity was demonstrated with oxygen reduction occurring at E1/2 = 0.45 V and has an onset potential of 0.62 V vs. RHE.