Effect of ammonium ion distribution on Nafion® conductivity

Hongsirikarn, Kitiya; Napapruekchart, Thirapong; Mo, Xunhua; Goodwin, James G.

doi:10.1016/j.jpowsour.2010.07.080

Cited by 22 publications

(19 citation statements)

References 20 publications

(39 reference statements)

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“…[50,51] As the NRR continued, the generated ammonium may cause degradation of the Nafion membrane, whichi nt urn, would affect the NRR rates. [50,51] As the NRR continued, the generated ammonium may cause degradation of the Nafion membrane, whichi nt urn, would affect the NRR rates.…”

Section: Resultsmentioning

confidence: 99%

Highly Selective Electrochemical Reduction of Dinitrogen to Ammonia at Ambient Temperature and Pressure over Iron Oxide Catalysts

Cui

Tang

Liu

et al. 2018

Chemistry A European J

134

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The catalytic conversion of dinitrogen (N ) into ammonia under ambient conditions represents one of the Holy Grails in sustainable chemistry. As a potential alternative to the Haber-Bosch process, the electrochemical reduction of N to NH is attractive owing to its renewability and flexibility, as well as its sustainability for producing and storing value-added chemicals from the abundant feedstock of water and nitrogen on earth. However, owing to the kinetically complex and energetically challenging N reduction reaction (NRR) process, NRR electrocatalysts with high catalytic activity and high selectivity are rare. In this contribution, as a proof-of-concept, we demonstrate that both the NH yield and faradaic efficiency (FE) under ambient conditions can be improved by modification of the hematite nanostructure surface. Introducing more oxygen vacancies to the hematite surface renders an improved performance in NRR, which leads to an average NH production rate of 0.46 μg h cm and an NH FE of 6.04 % at -0.9 V vs. Ag/AgCl in 0.10 m KOH electrolyte. The durability of the electrochemical system was also investigated. A surprisingly high average NH production rate of 1.45 μg h cm and a NH FE of 8.28 % were achieved after the first 1 h chronoamperometry test. This is among the highest FEs reported so far for non-precious-metal catalysts that use a polymer-electrolyte-membrane cell and is much higher than the FE of precious-metal catalysts (e.g., Ru/C) under comparable reaction conditions. However, the NH yield and the FE dropped to 0.29 μg h cm and 2.74 %, respectively, after 16 h of chronoamperometry tests, which indicates poor durability of the system. Our results demonstrate the important role that the surface states of transition-metal oxides have in promoting electrocatalytic NRR under ambient conditions. This work may spur interest towards the rational design of electrocatalysts as well as electrochemical systems for NRR, with emphasis on the issue of stability.

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Section: Resultsmentioning

confidence: 99%

Highly Selective Electrochemical Reduction of Dinitrogen to Ammonia at Ambient Temperature and Pressure over Iron Oxide Catalysts

Cui

Tang

Liu

et al. 2018

Chemistry A European J

134

View full text Add to dashboard Cite

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“…Soto et al [22] also drew the conclusion that the conductivity effect is the major cause of fuel cell degradation induced by ammonia contamination, whereas the major impact of CO [23e25] and H 2 S [26e28] contaminants on MEA performance is widely reported to be kinetic. As a result, Halseid et al [18] and Hongsirikarn [29,30] explored the ammonium/ammonia influence on membrane conductivities. Their findings indicated that the effect of ammonium ion distribution on Nafion Ò conductivity under typical fuel cell conditions can be significant [29], and that humidity and NH 4 þ content appear to have a concerted effect on conductivity [30].…”

Section: Introductionmentioning

confidence: 99%

“…As a result, Halseid et al [18] and Hongsirikarn [29,30] explored the ammonium/ammonia influence on membrane conductivities. Their findings indicated that the effect of ammonium ion distribution on Nafion Ò conductivity under typical fuel cell conditions can be significant [29], and that humidity and NH 4 þ content appear to have a concerted effect on conductivity [30]. Although Zhang et al [31,32] found that ammonia also affected the hydrogen adsorption and Pt oxidation reaction at the cathode, and NH 3 (or NH 4 þ ) could adsorb onto the Pt surface, which in turn decreased the catalyst's active area, the effect of ammonia adsorption on the catalyst layers could mostly be reversed, whereas the membrane was not easily cleaned.…”

Section: Introductionmentioning

confidence: 99%

Diagnosis of contamination introduced by ammonia at the cathode in a polymer electrolyte membrane fuel cell

Yuan

et al. 2012

International Journal of Hydrogen Energy

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“…Furthermore, unequally poisoned membranes were examined by using a two‐probe ac technique with a potentiostat 35. This should provide better insight in real conditions because it is assumed that NH 3 is rapidly deposited near the inlet and not distributed within the cell.…”

Section: Review On Air Pollutants and Their Influence On Pemfcmentioning

confidence: 99%

Sensitivity Analyses on the Impact of Air Contaminants on Automotive Fuel Cells

et al. 2016

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It is known that traffic related air contaminants cause power loss, decreasing lifetime or a complete failure of proton exchange membrane fuel cell (PEMFC). Therefore, the present study aims for a better understanding and the development of a data basis for further decisions in dealing with air contaminants for automobile applications. The first section provides an overview of scientific literature about the influence of important air contaminants on proton exchange membrane fuel cells (PEMFC). The second section describes an extensive study of air contaminants at possible automotive operating conditions using a full factorial matrix test. The specific variation of temperature, cell potential and harmful gas concentration resulted in 27 operating points for each used air contaminant. The gases NO, NO2, SO2, NH3, toluene and ethane were used. The results indicate significant degradation but as well the possibility of regeneration. The degradation caused by different harmful gases is both, dependent on temperature and potential. Furthermore, a clear difference of the influence of NO and NO2 at low concentrations could be shown. The experiments give an overview of the cathode harming potential of relevant air contaminants. Hence, the work provides a basis for the development of cathode air filter and regeneration techniques for automotive applications.

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Effect of ammonium ion distribution on Nafion® conductivity

Cited by 22 publications

References 20 publications

Highly Selective Electrochemical Reduction of Dinitrogen to Ammonia at Ambient Temperature and Pressure over Iron Oxide Catalysts

Highly Selective Electrochemical Reduction of Dinitrogen to Ammonia at Ambient Temperature and Pressure over Iron Oxide Catalysts

Diagnosis of contamination introduced by ammonia at the cathode in a polymer electrolyte membrane fuel cell

Sensitivity Analyses on the Impact of Air Contaminants on Automotive Fuel Cells

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