Experimental and theoretical investigations on the anti-perovskite nitrides Co3CuN, Ni3CuN and Co3MoN for ammonia synthesis.
Experimental and theoretical investigations on the anti-perovskite nitrides Co3CuN, Ni3CuN and Co3MoN for ammonia synthesis.
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用于氨合成的反钙钛矿氮化物 Co3CuN、Ni3CuN 和 Co3MoN 的实验和理论研究。
DOI：
10.1039/d2fd00151a
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发表时间：
2023
影响因子：
3.4
通讯作者：
Daisley A
中科院分区：
文献类型：
--
作者：
Daisley A
比较了反钙钛矿氮化物Co 3CuN和Ni 3CuN的氨合成活性，以探讨可能的金属组成-活性关系。反应后元素分析表明，这两种氮化物的活性是由于晶格氮的损失，而不是催化过程。观察到Co 3CuN比Ni 3CuN将更高百分比的晶格氮转化为氨，并且在较低温度下具有活性。反应过程中晶格氮的损失是拓扑的，并形成了Co 3Cu和Ni 3Cu。因此，反钙钛矿氮化物作为用于通过化学循环形成氨的试剂可能是有意义的。氮化物的再生是通过相应的金属合金的氨解来实现的。然而，使用N2的再生显示出挑战性。为了理解两种氮化物之间的反应性差异，应用DFT技术来研究晶格氮经由转化成N2或NH3而演变成气相所涉及的过程的热力学，揭示了反钙钛矿向合金相的本体转化的能量学的关键差异，以及从稳定的低折射率N-端接的（111）和（100）面损失表面N。在费米能级的态密度（DOS）的计算建模进行。结果表明，Ni和Co的d态对态密度有贡献，而Cu的d态只对态密度有贡献.反钙钛矿Co 3 MoN已被研究，作为与Co 3 Mo 3 N的比较，可以深入了解结构类型在氨合成活性中所起的作用。合成材料的XRD图案和元素分析显示存在含有氮的非晶相。与Co 3CuN和Ni 3CuN相比，该材料在400 °C下具有稳态活性，速率为92 ± 15 μmol h−1 g−1。因此，看来金属组成对反钙钛矿氮化物的稳定性和活性具有影响。
The ammonia synthesis activities of the anti-perovskite nitrides Co3CuN and Ni3CuN have been compared to investigate the possible metal composition–activity relationship. Post-reaction elemental analysis showed that the activity for both nitrides was due to loss of lattice nitrogen rather than a catalytic process. Co3CuN was observed to convert a higher percentage of lattice nitrogen to ammonia than Ni3CuN and was active at a lower temperature. The loss of lattice nitrogen was revealed to be topotactic and Co3Cu and Ni3Cu were formed during the reaction. Therefore, the anti-perovskite nitrides may be of interest as reagents for the formation of ammonia through chemical looping. The regeneration of the nitrides was achieved by ammonolysis of the corresponding metal alloys. However, regeneration using N2 was shown to be challenging. In order to understand the difference in reactivity between the two nitrides, DFT techniques were applied to investigate the thermodynamics of the processes involved in the evolution of lattice nitrogen to the gas phase via conversion to N2 or NH3, revealing key differences in the energetics of bulk conversion of the anti-perovskite to the alloy phase, and in loss of surface N from the stable low-index N-terminated (111) and (100) facets. Computational modelling of the density of states (DOS) at the Fermi level was performed. It was shown that the Ni and Co d states contributed to the density of states and that the Cu d states only contributed to the DOS for Co3CuN. The anti-perovskite Co3MoN has been investigated as comparisons with Co3Mo3N may give an insight into the role structure type plays in the ammonia synthesis activity. The XRD pattern and elemental analysis for the synthesised material revealed that an amorphous phase was present that contained nitrogen. In contrast to Co3CuN and Ni3CuN, the material was shown to have steady state activity at 400 °C with a rate of 92 ± 15 μmol h−1 g−1. Therefore, it appears that metal composition has an influence on the stability and activity of the anti-perovskite nitrides.