A cobalt–pyrrole coordination compound as high performance cathode catalyst for direct borohydride fuel cells

Abstract

Pyrrole and cobalt nitrate were used as nitrogen and metal sources respectively to synthesize a dinitratobis(polypyrrole)cobalt(II) (Co(polypyrrole)₂(NO₃)₂) adduct as the precursor of a Co–pyrrole/MPC catalyst. Pyrrole has the capability of polymerization and coordination with Co(II). Taking this advantage, the Co(polypyrrole)₂(NO₃)₂ coordination can form a long-chain structure with abundant and robust Co–N bonds, contributing to significantly increased catalytic sites in the product catalyst. As a result, the obtained Co–pyrrole/MPC (MPC = macroporous carbon) catalyst exhibited high ORR catalytic activity in alkaline media and excellent performance in direct borohydride fuel cell (DBFC). A peak power density up to 325 mW cm⁻² was achieved at ambient condition, outperforming the commercialized Pt/XC-72 benchmark containing 28.6 wt% Pt. The construction of long-chain coordination precursor was verified playing a key role in the electrochemical improvement of Co–pyrrole/MPC catalyst in DBFC.