The Preparation Of Non-platinum Catalysts And Their Application For Oxygen Reduction Reaction In Fuel Cell

To achieve the commercialization of low-temperature polymer electrolyte membrane fuel cells, developing non-precious metal(NPM) catalysts with pronounced catalytic performance toward oxygen reduction reaction(ORR) to substitute conventional Pt is of great importance. In this paper, we prepared a doped carbon catalyst which has hollow spherical morphology, high surface area, hierarchical porous structure, using iron phthalocyanines(Fe Pc) impregnated/covered zeolitic imidazolate framework nanocrystals(Z8Nc) as precursor. Our strategy introduced abundant Fe–Nx active species into/onto the highly porous N-rich nanocrystals and improved the dispersibility of iron phthalocyanines. The introduction of Fe Pc into Z8 Nc played a crucial role in the structural evolution of the resulting hollow-core porous carbon as well as the improvement of the catalytic performance. Doped carbon catalysts derived from either Z8 Nc or Fe Pc exhibit poor activity towards oxygen reduction, whereas the catalyst derived from Z8 Nc impregnated/covered with Fe Pc exhibits extremely high performance in both acidic and alkaline media. Recently, NPM catalysts with high ORR performance in alkaline medium are widely reported, however, developing NPM catalysts with high ORR performance in acid is still a big challenge. In 0.1 M HCl O4, the half-potential of our catalyst was only 60 m V lower than that of 20 wt% Pt/C catalyst. In 0.1 M KOH, its ORR activity even surpassed that of Pt/C, the half-potential was 35 m V higher than that of Pt/C. Its performances in both acidic and alkaline media rank among the best of those reported for NPM catalysts. We suggest that the high performance of the catalyst is attributable to the following factors:(i) the high active site density caused by doping Fe Pc into/onto the highly porous, N-rich Z8 Nc,(ii) the high surface area and adequate active site exposure caused by its hollow spherical morphology, and(iii) the hierarchical porous structure which further facilitates the diffusion and adsorption of oxygen molecules and enhances the mass transport of ORR. We also prepared a catalyst by pyrolyzing Fe Pc supported on the carbonized Z8 Nc, it showed anomalous granular morphology and its performance was lower than that of the catalyst prepared by pyrolyzing Fe Pc impregnated/covered Z8 Nc. We also prepared a catalyst by pyrolyzing Cu Pc impregnated/covered Z8 Nc, it showed porous nano-particle morphology and exhibited good ORR activity in alkaline media.