Kirste KG, Laassiri S, Hu Z, Stoian D, Torrente-Murciano L, Hargreaves JSJ, Mathisen K. XAS investigation of silica aerogel supported cobalt rhenium catalysts for ammonia decomposition.
Phys Chem Chem Phys 2020;
22:18932-18949. [PMID:
32567607 DOI:
10.1039/d0cp00558d]
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Abstract
The implementation of ammonia as a hydrogen vector relies on the development of active catalysts to release hydrogen on-demand at low temperatures. As an alternative to ruthenium-based catalysts, herein we report the high activity of silica aerogel supported cobalt rhenium catalysts. XANES/EXAFS studies undertaken at reaction conditions in the presence of the ammonia feed reveal that the cobalt and rhenium components of the catalyst which had been pre-reduced are initially re-oxidised prior to their subsequent reduction to metallic and bimetallic species before catalytic activity is observed. A synergistic effect is apparent in which this re-reduction step occurs at considerably lower temperatures than for the corresponding monometallic counterpart materials. The rate of hydrogen production via ammonia decomposition was determined to be 0.007 molH2 gcat-1 h-1 at 450 °C. The current study indicates that reduced Co species are crucial for the development of catalytic activity.
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