Decomposition of NH3 on Pd and Ir Comparison with Pt and Rh

Papapolymerou, G.; Bontozoglou, V.

doi:10.1016/s1381-1169(96)00428-1

Cited by 109 publications

(63 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…48 The zero point energy correction reduces the value of the adsorption energy by ∼10 kJ mol -1 . The adsorption energy on the (100) surface is always higher than that on the (111) surface for all of the metals, although the differences between the two planes over the same metal are relatively small (<12 kJ mol -1 ).…”

Section: Resultsmentioning

confidence: 99%

“…The decomposition of NH 3 into N 2 and H 2 has been investigated over polycrystalline Pt, Rh, and Pd wires in a differential flow reactor, at pressures from 0.01 to 1 Torr and temperatures from 500 to 1900 K. 48 It has been found that Rh is more active than Pt and Pd and that the rate of product formation can be described by a Langmuir-Hinshelwood unimolecular model. The determined heats of NH 3 adsorption are very similar over the three metals (67-71 kJ mol -1 ).…”

Section: ) and Height From The Surface Layer (Z) (Distances In Angstmentioning

confidence: 99%

See 1 more Smart Citation

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NH_x Species

et al. 2006

View full text Add to dashboard Cite

Periodic DFT calculations using plane waves have been applied to comparatively study the adsorption and decomposition of ammonia on the (111) and (100) surfaces of platinum-group metals (Pd, Rh, Pt). Different adsorption geometries and positions have been studied for NH 3 and its dehydrogenation intermediates (NH x , x ) 0, 1, 2). On the six surfaces investigated, NH 3 adsorbs preferentially on top sites, NH 2 on bridge, and NH and N on hollow sites. However, the adsorption energies of the NH x moieties differ considerably from one surface to another. All of the species adsorb more strongly on the (100) than on the (111) planes. Rh(100) provides the maximum stability for the various intermediates. The reaction energies, the structure of the transition states, and the activation barriers of the successive dehydrogenation steps (NH x f NH x-1 + H) have been determined, making it possible to compute rate coefficients at different temperatures. Our calculations have confirmed that ammonia decomposition over noble metal catalysts is structure sensitive. As a general trend, the first dehydrogenation step is rate determining, especially for Pd. In agreement with experiments, Rh is a better catalyst for NH 3 decomposition than are Pt and Pd. The former strongly stabilizes the highly dehydrogenated NH and N species and also leads to the lowest activation barriers. For the set of dehydrogenation reactions, a linear relationship between the transition state potential energy and the adsorption energy of the final state has been obtained.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: ) and Height From The Surface Layer (Z) (Distances In Angstmentioning

confidence: 99%

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NH_x Species

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Their investigation showed that Ir wires were far more active than Pd, Pt and Rh. Also comparison with previous studies show higher ammonia decomposition rates on Ir [91,92] as opposed to Ni wires [93]. This motivated us to investigate the ammonia decomposition process on Ir single crystal surfaces [15].…”

Section: Catalytic Decomposition Of Ammoniamentioning

confidence: 55%

“…Recently, Papapolymerou and Bontozoglou have compared the ammonia decomposition activity for various metal wires [91]. Their investigation showed that Ir wires were far more active than Pd, Pt and Rh.…”

Section: Catalytic Decomposition Of Ammoniamentioning

confidence: 99%

CO-free fuel processing for fuel cell applications

2003

Fuel and Energy Abstracts

View full text Add to dashboard Cite

In view of the stringent CO intolerance of the state-of-the-art proton exchange membrane (PEM) fuel cells, it is desirable to explore CO-free fuel processing alternatives. In recent years, step-wise reforming of hydrocarbons has been proposed for production of CO-free hydrogen for fuel cell applications. The decomposition of hydrocarbons (first step of the step-wise reforming process) has been extensively investigated. Both steam and air have been employed for catalyst regeneration in the second step of the process. Since, PEM is poisoned by very low (ppm) levels of CO, it is essential to eliminate even trace amounts of CO from the reformate stream. Preferential oxidation of CO (PROX) is considered to be a promising method for trace CO clean up. Related studies along with a discussion of catalytic ammonia decomposition (for applications in alkaline fuel cells) will be included in this review.

show abstract

“…All studies are based on an ammonia gas hourly space velocity (GHSV) of 30,000 ml/h/g of catalyst except (a) GHSV = 150,000 ml/h/g and (b) GHSV = 60,000 ml/h/g. Papapolymerou and Bontozoglou [9] studied the rate of decomposition at 225 -925 °C and 133 kPa ammonia partial pressure. They used the catalyst in the form of polycrystalline wires of foils, and ranked them in decreasing order of reaction rate: Ir > Rh > Pt > Pd.…”

Section: Catalytic Decomposition Of Ammoniamentioning

confidence: 99%

Ammonia as a Hydrogen Source for Fuel Cells: A Review

Cheddie¹

2012

Hydrogen Energy - Challenges and Perspectives

View full text Add to dashboard Cite

Decomposition of NH3 on Pd and Ir Comparison with Pt and Rh

Cited by 109 publications

References 14 publications

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NH_x Species

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NH_x Species

CO-free fuel processing for fuel cell applications

Ammonia as a Hydrogen Source for Fuel Cells: A Review

Contact Info

Product

Resources

About

Decomposition of NH3 on Pd and Ir Comparison with Pt and Rh

Cited by 109 publications

References 14 publications

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NHx Species

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NHx Species

CO-free fuel processing for fuel cell applications

Ammonia as a Hydrogen Source for Fuel Cells: A Review

Contact Info

Product

Resources

About

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NH_x Species

Ammonia Dehydrogenation over Platinum-Group Metal Surfaces. Structure, Stability, and Reactivity of Adsorbed NH_x Species