COx-free hydrogen production from ammonia on novel cobalt catalysts supported on 1D titanate nanotubes
COx-free hydrogen production from ammonia on novel cobalt catalysts supported on 1D titanate nanotubes
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DOI：
10.1016/j.ijhydene.2019.09.120
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发表时间：
2019-11
影响因子：
7.2
通讯作者：
H. A. Lara-García;J. A. Mendoza-Nieto;H. Pfeiffer;L. Torrente‐Murciano
中科院分区：
文献类型：
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作者：
H. A. Lara-García;J. A. Mendoza-Nieto;H. Pfeiffer;L. Torrente‐Murciano
如果可以设计一种可持续且高效的催化剂来按需释放不含 COx 的氢气，那么以氨等化学键储存氢是物理氢储存的一种有吸引力的替代方案。本文提出了钴基催化剂设计的系统研究，摆脱了稀缺的钌基系统。它证明了钴基催化剂的制备方法不仅对于调节活性物种的尺寸及其与载体的相互作用的重要性，而且对于促进活性物种的重要性。通过离子交换方法负载在钛酸盐纳米管上的钴导致钴并入钛酸盐的晶体结构中，促进不可还原的钛酸钴物质的形成，这对钛酸盐载体的反应性和热稳定性产生不利影响。通过使用 NaOH 方法沉积-沉淀负载钴，可以实现相当高的反应活性，导致在钛酸盐纳米棒载体表面形成可还原的钴颗粒。在这种情况下，反应速率与钴颗粒尺寸成反比，这表明钴基催化剂颗粒尺寸对氨分解制氢的关键影响。尽管这里报道的钴基催化剂的活性仍然低于最先进的钌对应系统，但这项工作为未来开发使用氨作为氢载体的可持续催化剂提供了独特的见解。
Hydrogen storage in chemical bonds such as ammonia is an attractive alternative to physical hydrogen storage if a sustainable and efficient catalyst can be designed for the release of COx-free hydrogen on demand. This paper presents a systematic study for the design of cobalt-based catalysts, moving away from scare Ru-based systems. It demonstrates the importance of the preparation method of cobalt-based catalysts not only to tune the size of the active species and their interaction with the support but also in the promotion of active species. Cobalt supported on titanate nanotubes via an ion-exchange method leads to the incorporation of the cobalt into the crystal structure of the titanates facilitating the formation of unreducible cobalt titanate species with a detrimental effect on the reactivity, and the thermal stability of the titanate support. Considerably higher reactivities can be achieved by loading cobalt via deposition-precipitation with NaOH method, leading to the formation of reducible cobalt particles on the surface of the titanate nanorods support. In this case, the rate of reaction is inversely related to the cobalt particle size, pointing out the key effect of particle size of cobalt-based catalyst for the hydrogen production in ammonia decomposition. Although the activities reported here for cobalt-based catalysts are still below those of the state-of-the-art ruthenium counterpart systems, this work provides unique insights for the future development of sustainable catalysts for the use of ammonia as hydrogen vector.