High pressure pyrolyzed non-precious metal oxygen reduction catalysts for alkaline polymer electrolyte membrane fuel cells

Abstract

Non-precious metal catalysts, such as metal-coordinated to nitrogen doped-carbon, have shown reasonable oxygen reduction reaction (ORR) performances in alkaline fuel cells. In this report, we present the development of a highly active, stable and low-cost non-precious metal ORR catalyst by direct synthesis under autogenic-pressure conditions. Transmission electron microscopy studies show highly porous Fe-N-C and Co-N-C structures, which were further confirmed by Brunauer-Emmett-Teller surface area measurements. The surface areas of the Fe-N-C and Co-N-C catalysts were found to be 377.5 and 369.3 m(2) g(-1), respectively. XPS results show the possible existence of N-C and M-Nx structures, which are generally proposed to be the active sites in non-precious metal catalysts. The Fe-N-C electrocatalyst exhibits an ORR half-wave potential 20 mV higher than the reference Pt/C catalyst. The cycling durability test for Fe-N-C over 5000 cycles shows that the half-wave potential lost only 4 mV, whereas the half-wave potential of the Pt/C catalyst lost about 50 mV. The Fe-N-C catalyst exhibited an improved activity and stability compared to the reference Pt/C catalyst and it possesses a direct 4-electron transfer pathway for the ORR process. Further, the Fe-N-C catalyst produces extremely low HO2(-) content, as confirmed by the rotating ring-disk electrode measurements. In the alkaline fuel single cell tests, maximum power densities of 75 and 80 mW cm(-2) were observed for the Fe-N-C and Pt/C cathodes, respectively. Durability studies (100 h) showed that decay of the fuel cell current was more prominent for the Pt/C cathode catalyst compared to the Fe-N-C cathode catalyst. Therefore, the Fe-N-C catalyst appears to be a promising new class of non-precious metal catalysts prepared by an autogenic synthetic method.

Poplar‐Catkin‐Derived N, P Co‐doped Carbon Microtubes as Efficient Oxygen Electrocatalysts for Zn‐Air Batteries

“…In a primary battery, the open‐circuit voltage (OCV) of NH 3 ‐treated NP‐CT‐1000 is 1.42 V (Figure a); this value is comparable to that of Pt/C (1.47 V). This comparison indicates the higher intrinsic ORR activity of Pt/C, which is consistent with the RDE measurements (Figure a). In addition, its peak power density is 125 mW cm −2 , which exceeds those of the recently reported ZABs, such as Fe, N doped carbon nanofibers‐based ZAB (86 mW cm −2 ), N, P doped honeycomb‐like carbon‐based ZAB (36.6 mW cm −2 ) and Fe, N doped metal organic framework@carbon nanotubes/graphene hybrid‐based ZAB (95.3 mW cm −2 ).…”

Effect of pyrolysis pressure on activity of Fe–N–C catalysts for oxygen reduction

“…18,19,33,34,35,36 All LSVs were obtained at a 0.5 mV s -1 scan rate. Such a slow scan eliminates capacitive background current without additional corrections.…”

Elucidating Hydrogen Oxidation/Evolution Kinetics in Base and Acid by Enhanced Activities at the Optimized Pt Shell Thickness on the Ru Core

“…1,2 A possible alternative is employing an anion exchange membrane (AEM) 3,4 that offers a less corrosive environment, so enabling the incorporation of non-PGM catalysts for oxygen reduction and evolution. Recent advances demonstrated activities comparable to that of platinum (Pt) for oxygen reduction in AEM fuel cells, [5][6][7][8][9] and to that of iridium oxide for oxygen evolution in AEM water electrolyzers. [10][11][12][13][14] However, for the hydrogen oxidation reaction (HOR) and the hydrogen evolution reaction (HER), Pt's activity remains superior to that of the non-PGM catalysts, 3 even though it is lower by two orders-of-magnitude from that in an acid environment.…”