Ammonia decomposition over cobalt/carbon catalysts—Effect of carbon support and electron donating promoter on activity

Abstract

Please cite this article in press as: L. Torrente-Murciano, et al., Ammonia decomposition over cobalt/carbon catalysts-Effect of carbon support and electron donating promoter on activity, Catal. Today (2016), http://dx. a b s t r a c tThis paper sets the new design parameters for the development of low temperature ammonia decomposition catalysts based on readily available cobalt as an alternative to scarce but highly active ruthenium-based catalysts. By using a variety of carbon materials as catalytic supports, we systematically demonstrate that microporous supports capable of stabilising small cobalt crystallites (∼2 nm) lead to high catalytic activities compared to bigger nanoparticles. Additionally, the degree of graphitisation of the carbon support has a detrimental effect on the activity of the cobalt (0) active sites, likely due to their potential as an electron donator. Consequently, the addition of electron donating promoters such as cesium substantially decreases the activity of the cobalt catalysts. This relationship deviates from the trends observed for ruthenium-based catalysts with an optimum 3-5 nm size where an increase of the graphitisation degree of the support and the addition of electron donating promoters increases the ammonia decomposition activity.

Kinetic and mechanistic analysis of NH3decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

“…Extensive studies have shed light on the ammonia decomposition mechanisms on various metals, such as Fe, [7][8][9] Ni, [10][11][12][13] Co, 14,15 Cu(111), 16 Pd(111), 17 Pt, 18 Rh(111), 19 Ru(0001) [20][21][22][23][24][25][26][27] and Ir. [28][29][30][31][32] Boisen employed a model describing the catalytic trends over transition metal catalysts and found Ru to be the most active metal for this reaction.…”

Carbon Aerogel-Supported Nickel and Iron for Gasification Gas Cleaning. Part I: Ammonia Adsorption

“…More detailed studies on metal-ammonia interaction have been published using theoretical ways, in which the effect of support is not considered. Results suggest that the adsorption of ammonia on transition metal atoms, like Fe and Ni, occurs in bridge, hollow, and top positions, through the unpaired electrons in nitrogen [56][57][58]. Their results suggest a chemical interaction between ammonia and metals supported by calculated thermodynamics parameters.…”

Effect of Alkali Metal Addition to a Ru/CeO₂ Catalyst Prepared by NaBH₄ Reduction on the Catalytic Performance for H₂ Production via NH₃ Decomposition

“…Yin et al (2004b) found that a multiwall carbon nanotube-supported Ru catalyst exhibited the best performance for catalytic NH 3 decomposition among the catalysts they tested. Moreover, the catalytic performance of supported metal catalysts has been improved by adding promoters (Raróg-Pilecka et al, 2003;Sørensen et al, 2006;Huang et al, 2013;Mukherjee et al, 2018;Su et al, 2018;Hu et al, 2019;McCullough et al, 2020) and by modifying the support (Yin et al, 2004a;García-García et al, 2010;Armenise et al, 2012;Marco et al, 2013;Bell et al, 2017;Ren et al, 2017;Mukherjee et al, 2018;Su et al, 2018;Sima et al, 2020). Although most studies focus on Ru or Ni metal as the active site for NH 3 decomposition to produce H 2 (Choudhary et al, 2001;Raróg-Pilecka et al, 2003;Yin et al, 2004aYin et al, , 2004bSørensen et al, 2006;García-García et al, 2010;Armenise et al, 2012;Huang et al, 2013;Marco et al, 2013;Nakamura and Fujitani, 2016;Okura et al, 2016;Takahashi and Fujitani, 2016;Bell et al, 2017;Ren et al, 2017;Mukherjee et al, 2018;Su et al, 2018;Hu et al, 2019;Lucentini et al, 2019;McCullough et al, 2020;Sima et al, 2020), supported nonnoble metal catalysts and transition metal…”

“…Although most studies focus on Ru or Ni metal as the active site for NH 3 decomposition to produce H 2 (Choudhary et al, 2001;Raróg-Pilecka et al, 2003;Yin et al, 2004aYin et al, , 2004bSørensen et al, 2006;García-García et al, 2010;Armenise et al, 2012;Huang et al, 2013;Marco et al, 2013;Nakamura and Fujitani, 2016;Okura et al, 2016;Takahashi and Fujitani, 2016;Bell et al, 2017;Ren et al, 2017;Mukherjee et al, 2018;Su et al, 2018;Hu et al, 2019;Lucentini et al, 2019;McCullough et al, 2020;Sima et al, 2020), supported nonnoble metal catalysts and transition metal (Co, Fe, Mo, and Ni) nitride or carbide catalysts have been reported as active catalysts for producing H 2 via NH 3 decomposition (Podila et al, 2017;Srifa et al, 2017;Torrente-Murciano et al, 2017;Jolaoso et al, 2018;Lara-García et al, 2019). Although these catalysts are relatively inexpensive, they exhibit high performance for NH 3 decomposition only at temperatures above 823 K (Bell and Torrente-Murciano, 2016;Podila et al, 2017;Srifa et al, 2017;Torrente-Murciano et al, 2017;Jolaoso et al, 2018;Lara-García et al, 2019). ese inexpensive catalysts would be suitable for high-temperature applications, such as in solid oxide fuel cells with NH 3 as a fuel, but not for on-site H 2 production at low temperatures (Bell and Torrente-Murciano, 2016).…”