Intermediate Temperature Fuel Cell and Oxygen Reduction Studies With Carbon-Supported Platinum Alloy Catalysts in Phosphoric Acid Based Systems

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohamed Mamlouk ◽  
Jong Hyun Jang ◽  
Keith Scott
Keyword(s):  
Phosphoric Acid ◽  
Oxygen Reduction ◽  
Phosphoric Acid Solution ◽  
Open Circuit ◽  
Intermediate Temperature ◽  
Pt Catalyst ◽  
Platinum Alloy ◽  
Platinum Alloy Catalysts ◽  
Carbon Catalysts ◽  
Alloy Catalysts

The oxygen reduction activities of platinum and platinum alloy catalysts were evaluated at temperatures up to 150  °C in phosphoric acid solution. The oxygen reduction currents and open circuit potentials were measured using chronoamperometry with double potential steps to eliminate the effects of double layer charging currents and metal deactivationcould be eliminated effectively. Based on the mass activity at 0.7 V versus Ag/AgCl, the commercial PtNi catalyst showed higher performances than commercial Pt catalyst at 150 °C. The commercial PtCo catalyst showed high activities at 90 °C and 120 °C. Intermediate temperature fuel cells based on phosphoric acid doped polybenzimidazole membranes were tested with the alloy cathode catalysts. In the case of Pt–Fe alloy an enhanced performance was achieved in comparison to that with Pt carbon catalysts.

scholarly journals Platinum Alloy Catalysts for Oxygen Reduction Reaction: Advances, Challenges and Perspectives

ChemNanoMat ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 32-41 ◽  
Author(s):  
Dezhen Wu ◽  
Xiaochen Shen ◽  
Yanbo Pan ◽  
Libo Yao ◽  
Zhenmeng Peng
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Platinum Alloy ◽  
Platinum Alloy Catalysts ◽  
Alloy Catalysts

scholarly journals Synthesis of P- and N-doped carbon catalysts for the oxygen reduction reaction via controlled phosphoric acid treatment of folic acid

2019 ◽  
Author(s):  
Rieko Kobayashi ◽  
Takafumi Ishii ◽  
Yasuo Imashiro ◽  
Jun-ichi Ozaki
Keyword(s):  
Folic Acid ◽  
Phosphoric Acid ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Acid Treatment ◽  
Reduction Reaction ◽  
P Content ◽  
Orr Activity ◽  
Carbon Catalysts ◽  
Pyridinic N

Herein, we synthesized N- and P-doped carbons (PN-doped carbons) by controlled phosphoric acid treatment (CPAT) of folic acid (FA) and probed their ability to catalyze the oxygen reduction reaction at the cathode of a fuel cell. Precursors obtained by heating FA in the presence of phosphoric acid at temperatures of 400–1000 °C were further annealed at 1000 °C to afford PN-doped carbons. The extent of precursor P-doping was maximized at 700 °C, and the use of higher temperatures resulted in activation and increased porosity rather than in increased P content. The P/C atomic ratios of PN-doped carbons were well correlated with those of precursors, which indicated that CPAT was well suited for the preparation of PN-doped carbons. Carbon prepared using a CPAT temperature of 700 °C exhibited the highest oxygen reduction reaction (ORR) activity and was shown to contain –C–PO2 and –C–PO3 moieties as the major P species and pyridinic N as the major N species; moreover, no N–P bonds were detected. The presence of –C–PO2 and –C–PO3 units was concluded to decrease the work function and thus raise the Fermi level above the standard O2/H2O reduction potential, which resulted in enhanced ORR activity. Finally, CPAT was concluded to be applicable to the synthesis of PN-doped carbons from N-containing organic compounds other than FA.

scholarly journals Synthesis of P- and N-doped carbon catalysts for the oxygen reduction reaction via controlled phosphoric acid treatment of folic acid

2019 ◽  
Vol 10 ◽  
pp. 1497-1510 ◽  
Author(s):  
Rieko Kobayashi ◽  
Takafumi Ishii ◽  
Yasuo Imashiro ◽  
Jun-ichi Ozaki
Keyword(s):  
Folic Acid ◽  
Phosphoric Acid ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Acid Treatment ◽  
Carbon Materials ◽  
Reduction Reaction ◽  
P Content ◽  
Orr Activity ◽  
Carbon Catalysts

Herein, we synthesized P- and N-doped carbon materials (PN-doped carbon materials) through controlled phosphoric acid treatment (CPAT) of folic acid (FA) and probed their ability to catalyze the oxygen reduction reaction (ORR) at the cathode of a fuel cell. Precursors obtained by heating FA in the presence of phosphoric acid at temperatures of 400–1000 °C were further annealed at 1000 °C to afford PN-doped carbon materials. The extent of precursor P doping was maximized at 700 °C, and the use of higher temperatures resulted in activation and increased porosity rather than in increased P content. The P/C atomic ratios of PN-doped carbon materials correlated well with those of the precursors, which indicated that CPAT is well suited for the preparation of PN-doped carbon materials. The carbon material prepared using a CPAT temperature of 700 °C exhibited the highest ORR activity and was shown to contain –C–PO2 and –C–PO3 moieties as the major P species and pyridinic N as the major N species. Moreover, no N–P bonds were detected. It was concluded that the presence of –C–PO2 and –C–PO3 units decreases the work function and thus raises the Fermi level above the standard O2/H2O reduction potential, which resulted in enhanced ORR activity. Finally, CPAT was concluded to be applicable to the synthesis of PN-doped carbon materials from N-containing organic compounds other than FA.

scholarly journals Warped graphitic layers generated by oxidation of fullerene extraction residue and its oxygen reduction catalytic activity

2019 ◽  
Vol 10 ◽  
pp. 1391-1400 ◽  
Author(s):  
Machiko Takigami ◽  
Rieko Kobayashi ◽  
Takafumi Ishii ◽  
Yasuo Imashiro ◽  
Jun-ichi Ozaki
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Oxidation Time ◽  
Pt Catalyst ◽  
Oxidation Treatment ◽  
Orr Activity ◽  
Temperature Programmed ◽  
Carbon Catalysts

Carbon-based oxygen reduction reaction (ORR) catalysts are regarded as a promising candidate to replace the currently used Pt catalyst in polymer electrolyte fuel cells (PEFCs); however, the active sites remain under discussion. We predicted that warped graphitic layers (WGLs) are responsible for the ORR catalytic activity in some carbon catalysts (i.e., carbon alloy catalysts (CACs)). To prove our assumption, we needed to use WGLs consisting of carbon materials, but without any extrinsic catalytic elements, such as nitrogen, iron, or cobalt, which effectively enhance ORR activity. The present study employed a fullerene extraction residue as a starting material to construct WGLs. The oxidation of the material at 600 °C exposed the WGLs by removing the surrounding amorphous moieties. Transmission electron microscopy (TEM) observations revealed the formation of WGLs by oxidation treatment at 600 °C in an O2/N2 stream. Extending the oxidation time increased the purity of the WGL phase, but also simultaneously increased the concentration of oxygen-containing surface functional groups as monitored by temperature programmed desorption (TPD). The specific ORR activity increased with oxidation up to 1 h and then decreased with the intensive oxidation treatment. Correlations between the specific ORR activity and other parameters confirmed that the development of the WGL and the increase in the O/C ratio are the competing factors determining specific ORR activity. These results explain the maximum specific ORR activity after 1 h of oxidation time. WGLs were found to lower the heat of adsorption for O2 and to increase the occurrence of heterogeneous electron transfer.

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