Enhancement of the Catalytic Activity of Lithium Amide towards Ammonia Decomposition by Addition of Transition Metals
Enhancement of the Catalytic Activity of Lithium Amide towards Ammonia Decomposition by Addition of Transition Metals
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DOI：
10.18573/jae.11
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发表时间：
2023-07
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通讯作者：
Caitlin Brooker-Davis;Joshua W. Makepeace;T. Wood
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作者：
Caitlin Brooker-Davis;Joshua W. Makepeace;T. Wood
氨催化分解制氢是利用氨作为零碳能源的重要过程。然而，目前的催化剂系统在操作条件、通用性和成本效率方面的可行性已被证明是一个问题。考虑到与过渡金属（Cr, Mn, Fe）复合的锂酰胺和亚胺的催化活性增强的机制不确定性，进行了催化和重量研究。超过氨分解的气体流量被量化，并用于区分非化学计量亚胺锂酰胺与其他竞争过程的形成程度。分析结果表明，与Mn和Cr复合可以降低从酰胺态锂到富亚胺相的初始组成转变，而与Fe复合则不能。因此，该体系最好被认为是促进亚胺锂，Cr和Mn的作用是降低富亚胺活性相的形成温度，从而提高催化活性。DOI: https://doi.org/10.18573/jae.11
The catalytic decomposition of ammonia to hydrogen is a vital process in the use of ammonia as a zero-carbon energy store. However, the viability of current catalyst systems in terms of operating conditions, versatility, and cost efficiency has proven an issue. Catalytic and gravimetric studies were conducted considering mechanistic uncertainty surrounding the enhanced catalytic activity reported for lithium amide and imide composited with transition metals (Cr, Mn, Fe). Gas flow in excess of ammonia decomposition was quantified and used to differentiate the extent of formation of non-stoichiometric lithium imide amide from other competing processes. This analysis showed the initial compositional transition from lithium amide to an imide-rich phase was reduced in temperature by compositing with Mn and Cr, but not with Fe. The system is, therefore, best considered as promoted lithium imide, with Cr and Mn acting to reduce the formation temperature of the active imide-rich phase such that the catalytic activity is enhanced. DOI: https://doi.org/10.18573/jae.11