Electrochemical Synthesis of Ammonia in Solid Electrolyte Cells

Garagounis, I.; Kyriakou, V.; Skodra, Aglaia; Vasileiou, E.; Stoukides, Michael

doi:10.3389/fenrg.2014.00001

Cited by 110 publications

(109 citation statements)

References 56 publications

(99 reference statements)

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“…The Haber-Bosch process was developed one hundred years ago [3] and employs Fe-based catalysts in the temperature range of 400-500 • C and at pressures of 130-170 bar [3][4][5]. The newer KAAP (Kellogg Advanced Ammonia Process) process uses a Ru-based catalyst at relatively lower pressures (<100 bar) [6].…”

Section: Introductionmentioning

confidence: 99%

“…The need for fast reaction rates dictates operation at high temperatures. On the other hand, the need for high equilibrium conversion dictates operation at low temperatures [4]. Although the reaction is exothermic, a significant energy input is required.…”

Section: Introductionmentioning

confidence: 99%

“…Most of these theoretical and experimental studies suggest that the rate determining step is the dissociation of dinitrogen on the catalyst surface [2,8]. Since the first industrial application, numerous researchers have contributed to the discovery and development of more efficient ammonia synthesis catalysts, which would allow operation at lower temperatures and, consequently, at lower pressures [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

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Progress in the Electrochemical Synthesis of Ammonia

et al. 2017

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Progress in the Electrochemical Synthesis of Ammonia

et al. 2017

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“…8 Although Nafion-based low temperature electrochemical ammonia synthesis has been demonstrated in several reports, [9][10][11][12][13][14][15] no systematic investigation of noble metal catalysts exists. 2 Further, the alkaline environment of hydroxide exchange membranes (HEMs) promises the employment of non-noble metal catalysts and no acid/base reaction between the produced ammonia and the membrane is expected.…”

mentioning

confidence: 99%

Electrochemical Nitrogen Reduction Reaction on Noble Metal Catalysts in Proton and Hydroxide Exchange Membrane Electrolyzers

Nash

Yang

Anibal

et al. 2017

J. Electrochem. Soc.

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Five noble metal catalysts (Pt/C, Ir/C, Pd/C, Ru/C, and Au/C) are evaluated for electrochemical nitrogen reduction reaction (ENRR) to produce ammonia in both proton exchange membrane (PEM) and hydroxide exchange membrane (HEM) electrolyzers (PEMELs and HEMELs). The competing hydrogen evolution reaction (HER) is found to be the dominant reaction on all catalysts tested in both PEMELS and HEMELs, which is consistent with recent computational predictions that metallic catalysts are unlikely to be selective for ENRR. With the increase of applied potentials, the rate of HER increase significantly, which suppresses the ENRR, leading to significant decreases of faradaic efficiencies. Leaching of quaternary ammonium from HEM is found to interfere with ammonia quantification, which necessitates a pretreatment protocol. Due to the relatively slow kinetics of HER in alkaline solution, faradaic efficiencies in HEMELs are generally higher than those in PEMELs. We believe that these results provide a solid baseline for future research on ENRR in both PEMELs and HEMELs. Ammonia synthesis is one of the foundational chemical processes to the human society, which is estimated to supported approximately 27% of the world's population over the past century.1 The development of the Haber-Bosch process revolutionized modern agriculture, 2 however, the centralized, energy and carbon intensive nature of the Haber-Bosch process 3-5 leaves many aspects to be desired. Distributed and modular ammonia synthesis via the electrochemical nitrogen reduction reaction (ENRR) at or close to ambient conditions, powered by renewable electricity, is an attractive alternative because it allows as-needed production of ammonia, and in turn N-fertilizers, from ubiquitously available resources, i.e., N 2 and water. 4 Widespread adoption of ENRR for ammonia production could drastically reduce the carbon footprint of agricultural activities. In addition, ENRR is compatible with the intermittency of renewable energy sources, e.g., solar and wind, as the ammonia and N-fertilizers can be produced and stored when renewable electricity is available.Electrochemical fixation of atmospheric nitrogen was first attempted in 1908 even before the establishment of the Haber-Bosch process, to make nitric acid via electric discharge. 6 Further studies of ENRR have generally been focused on high temperature proton conductors at 500• C, 7 however, the high operating temperature and the stability of ammonia at such conditions make it unsuitable for distributed deployment. Proton exchange membranes (PEMs) can achieve high proton conductivity (∼100 mS·cm −1 at 25 • C for Nafion) at ambient or slightly elevated temperatures, which opens the possibility for electrochemical ammonia synthesis at those mild conditions. 8 Although Nafion-based low temperature electrochemical ammonia synthesis has been demonstrated in several reports, 9-15 no systematic investigation of noble metal catalysts exists.2 Further, the alkaline environment of hydroxide exchange membranes (HEMs) promises the...

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“…Garagounis et al 20 summarized the test results of studies within the last 15 years using electrolyte cells. More than 30 electrolyte materials with 15 catalysts that were used as working electrodes (cathode) were tested.…”

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confidence: 99%

Electrochemical Synthesis of Ammonia in Molten Salt Electrolyte Using Hydrogen and Nitrogen at Ambient Pressure

Biçer

Dinçer

2017

J. Electrochem. Soc.

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In this study, the synthesis of ammonia (NH3) at ambient pressure using H2 and N2 is electrochemically achieved. The conducting and reaction media with molten salt consist of molten hydroxide as NaOH and KOH whereas the reaction temperature is varied in the range of 200°C to 255°C to investigate the impact of temperature on the ammonia production rate and hence performance. The porous nickel mesh electrodes having an area of 100 cm2 are used as cathode and anode where the supplied electricity is controlled using potentiostat/galvanostat. The maximum faradaic efficiency for ammonia synthesis is found to be 9.3% at 210°C corresponding to 6.53 × 10−10 mol/s cm2 ammonia evolution rate at 2 mA/cm2 current density with nano-Fe3O4 as the catalyst. Furthermore, the applied voltages and applied currents are varied to find the optimum experimental conditions for molten salt electrolyte based electrochemical ammonia synthesis.

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Electrochemical Synthesis of Ammonia in Solid Electrolyte Cells

Cited by 110 publications

References 56 publications

Progress in the Electrochemical Synthesis of Ammonia

Progress in the Electrochemical Synthesis of Ammonia

Electrochemical Nitrogen Reduction Reaction on Noble Metal Catalysts in Proton and Hydroxide Exchange Membrane Electrolyzers

Electrochemical Synthesis of Ammonia in Molten Salt Electrolyte Using Hydrogen and Nitrogen at Ambient Pressure

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