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Industrial relevant catalysis

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Haohong Duan
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Rational design of highly active, stable and inexpensive catalysts with abundant interfaces can have great potential to increase catalytic performance. Topological transformation of layered double hydroxides (LDHs) to the corresponding mixed metal oxides (MMO) offers an efficient strategy to achieve such interfaces. However, the formation and conversion of these heterostructured interfaces is lack of study and remains to be elusive. Herein, we report a detailed investigation of the topological transformation of LDHs. The as-prepared MMO with abundant interfaces can be modulated by calcination of ZnCo-LDH at different temperatures. Among them, the ZnCo-LDH calcinated at 200°C reveals the most abundant interfaces and exhibits excellent performance in electrochemical water oxidation. This work will deepen the understanding of the LDH topological transformation from the molecular level.
Haohong Duan
added 2 research items
The interfaces of heterogeneous catalysts provide great contribution in improving catalytic activity due to the existed edge and corner sites with less coordinative unsaturation active site. However, the active sites are generally limited due to the sub-optimal large lateral size and thickness. Heterosturctured catalysts with abundant heterostructure interfaces provide a possible protocol to address the above issue. Herein, we describe the successful fabrication of heterostructure of high-energy {112} faceted Co3O4 nanosheets (~20 nm) confined by highly active {001} faceted ZnO nanosheets, via calcination of ZnCo-layered double hydroxide. The resulting Co3O4/ZnO heterostructure exhibits outstanding performance in acceptorless dehydrogenative coupling reaction with > 99% yield. X-ray absorption fine structure and density functional theory calculations reveal that the high activity can be attributed to the exposure of the highly active (112) facets of Co3O4 and the abundant interfaces of Co3O4/ZnO heterostructure, in which the ZnO facilitates electron transfer and lowers the reaction barrier as electronic promoter.
Lithium extraction from salt lake brines is one of the most important pathways for obtaining Li-related products e.g. Li2CO3, LiOH and for further fabricating electric energy-storage products e.g. lithium ion batteries. The high Mg/Li ratio and high Mg content is the remarkable characteristics of Chinese salt lake in Qaidam Basin, which makes the Mg/Li separation and Li extraction rather difficult. Herein, we proposed a reaction-coupled separation technology for Mg/Li separation from the brine with a high Mg/Li ratio. The core idea of this technology is that the Mg2+ cations are reacted to form a solid via a nucleation-crystallization separation method. The solid product is MgAl-layered double hydroxide (MgAl-LDH), the widely-used and high-valued product in the family of LDHs. The Li+ cations are still left in the solution after Mg2+ cations are reacted with alkali solution accompanied by foreign Al3+ cations. That is to say that the Mg2+ cations can be incorporated into the layers of MgAl-LDH while Li+ cations cannot. The findings indicate that Mg2+ cations are almost completely extracted into the solid phase to form LDH. The Li+ cations remain in the solution having a weight loss less than 8%, which is the excellent level of Li extraction from the brine with a high Mg/Li ratio. The effects of reaction parameters e.g. ionic strength, nucleation rotating speed, Mg/Al ratio, crystallization temperature and time were investigated on the separation performance and lithium loss. The optimal conditions were derived for lower lithium loss and more outstanding Mg/Li separation performance, which can be a useful guide for environment-friendly and sustainable Li extraction from the brine.