XAS investigation of silica aerogel supported cobalt rhenium catalysts for ammonia decomposition.
XAS investigation of silica aerogel supported cobalt rhenium catalysts for ammonia decomposition.
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DOI：
10.1039/d0cp00558d
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发表时间：
2020-06
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通讯作者：
Karsten G Kirste;S. Laassiri;Zhigang Hu;D. Stoian;L. Torrente‐Murciano;J. Hargreaves;K. Mathisen
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文献类型：
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作者：
Karsten G Kirste;S. Laassiri;Zhigang Hu;D. Stoian;L. Torrente‐Murciano;J. Hargreaves;K. Mathisen
氨作为氢载体的实现依赖于活性催化剂的发展，以在低温下按需释放氢。作为钌基催化剂的替代品，本文报道了二氧化硅气凝胶负载的钴铼催化剂的高活性。XANES/EXAFS研究在氨原料存在的条件下进行的反应表明，在观察到催化活性之前，催化剂中预先还原的钴和铼成分在随后还原为金属和双金属之前最初被再氧化。与相应的单金属材料相比，这种再还原步骤在相当低的温度下发生，这是一种明显的协同效应。在450°C时，氨分解产氢率为0.007 molH2 gcat-1 h-1。目前的研究表明，还原Co对催化活性的发展至关重要。
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.