Investigation on Electron Distribution and Synergetic to Enhance Catalytic Activity in Bimetallic Ni(II)/Pd(II) Molecular Monolayer

Abstract

Novel graphene oxide (GO)‐supported ordered diimine Ni/Pd bimetallic monolayers with ratio of Ni to Pd atomic ratios (2136 : 1, 333 : 1 and 97 : 1) (denoted as GO‐Diimine‐Ni/Pd1, GO‐Diimine‐Ni/Pd2, GO‐Diimine‐Ni/Pd3) were fabricated and their catalytic performances and synergetic mechanism were systematic investigated. For the as‐prepared GO‐Diimine‐Ni/Pd1, that trace palladium complex was responded for changing the electronic environment, tuning catalytic actives and modifying the electronic states which could enhance the highlighted catalytic activity. The more dramatic aspect of the GO‐Diimine‐Ni/Pd1 with high efficient catalytic activity could be achieved even with atom ratio of Ni/Pd even in 2136 : 1 (TOFNi=21277 h−1; TOFPd=4.545×107 h−1), in which the noble Pd could almost be replaced by non‐noble Ni according to requirement for economic chemistry. Interestingly, the synergetic mechanism between nickel and palladium was that the electron of Pd may transfer to Ni, which is different from the conventional Pd/Ni for catalyzing coupling reaction. Especially, the formation of Ni0 around Pd (II) as active centers was proposed and its size could be controlled with adjusting the palladium content on the surface. The results exhibited that the synergic effect between Ni and Pd made it easy for Ni2+ reduced into Ni0. It was crucial for adjusting the catalytic activity by designing the fine structure of ligand, the supports selection and modulating the Pd content at the molecular level.

Biochar as heterogeneous support for immobilization of Pd as efficient and reusable biocatalyst in C–C coupling reactions

“…[25,26] The presence of a high density of carbonyl, hydroxyl and carboxylic acid groups on the biochar surface allows the modification of its surface via reaction with dopamine, alkoxysilane and other reagents which can be used as a support for the immobilization of catalysts or other substances. [33][34][35][36][37][38][39][40] The use of palladium-phosphine catalysts involves expensive, toxic and air-and moisture-sensitive procedures. Biochar is a stable solid in air atmosphere, at high temperature and in aqueous solution, and therefore biochar is an ideal catalyst support for organic processes occurring under harsh conditions.…”

A New ternary organometallic Pd(ii)/Fe(iii)/Ru(iii) self-assembly monolayer: the essential ensemble synergistic for improving catalytic activity

“…1 For hetero-bimetallic catalysts, an investigation on the relationship between their activity and structure is deeply studied for understanding the synergism between the different components. [2][3][4] Recently, the synergistic catalysis with trimetallic catalysts have received considerable interest, 5 and the real active centers remain unknown because each component is responsible for different steps in the overall transformation. 6 Meanwhile, there has been rapidly growing interest in multi-component catalysts, in which improving the activity and reducing expenses are considered to be key issues for heterogeneous catalyst, 7,8 and are particularly important for noble metals.…”

“…15 Therefore, substituting palladium with less expensive doped transition metals is expected for achieving higher activity and reducing the catalyst costs. For example, some economic transition metals include nickel with its charge-donating ability, 4,9 and the charge transferring and stabilizing property of Fe. 8,16 Ruthenium is one of the cheapest precious metals having broad application prospects, 17,18 and has long been considered as one of the effective components in a catalyst.…”

“…[38][39][40][41][42][43][44][45] Previous studies showed that the activity of the bimetallic catalysts, or their monolayer and their recyclability, could be enhanced by tuning their orientation of the organometallic molecular, component, morphology and distributions of the active species, relating to the electrical characteristics of the supports, ligands, and synergism of the mono-or hetero-bimetallic catalytic lms. 4,16,35,37,39,44,[46][47][48][49][50][51][52][53][54][55] By now, multicomponent catalysts have made great progress, such as multi-metallic NPs, who have more variables available for tuning their catalytic activity. 56 Research on introducing a third or fourth metal to the ordered catalytic molecular monolayer is limited.…”

Terpyridine-based Pd(ii)/Ni(ii) organometallic framework nano-sheets supported on graphene oxide—investigating the fabrication, tuning of catalytic properties and synergetic effects

“…24 Previous studies have shown that the catalytic activity of the heterobimetallic catalysts could be enhanced by tuning their composition, morphology and the relative distributions of electrons, which are related to the electrical characteristics of the ligand, supports, and the synergy of hetero-bimetals. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Appropriate supports could promise a high dispersion of metallic catalyst and the maximum utilization of noble materials has attracted much attention; 19,40 graphene oxide (GO) has been recognized as an ideal candidate for supporting various metals and their complexes. [41][42][43] Pd catalyst doped with Ni, Fe, Co or Cu, reduces the loading of Pd and signicantly enhances catalytic activity by adjusting the distance between nickel and palladium, charge distribution and the arrangement of active sites.…”