Graphitized nanocarbon-supported metal catalysts: synthesis, properties, and applications in heterogeneous catalysis

Abstract

Graphitized nanocarbon materials can be an ideal catalyst support for heterogeneous catalytic systems. Their unique physical and chemical properties, such as large surface area, high adsorption capacity, excellent thermal and mechanical stability, outstanding electronic properties, and tunable porosity, allow the anchoring and dispersion of the active metals. Therefore, currently they are used as the key support material in many catalytic processes. This review summarizes recent relevant applications in supported catalysts that use graphitized nanocarbon as supports for catalytic oxidation, hydrogenation, dehydrogenation, and C-C coupling reactions in liquid-phase and gas-solid phase-reaction systems. The latest developments in specific features derived from the morphology and characteristics of graphitized nanocarbon-supported metal catalysts are highlighted, as well as the differences in the catalytic behavior of graphitized nanocarbon-supported metal catalysts versus other related catalysts. The scientific challenges and opportunities in this field are also discussed. Keywords: nanocarbon materials; graphitized carbon supports; metal catalysts; hetergeneous catalysis INTRODUCTIONCarbon combines its atoms in diverse hybridization states (sp, sp 2 , sp 3 ) to form a variety of polymorphs. These are composed entirely of carbon but have different physical structures and different names, including diamond, graphite, fullerenes, and carbines, among others [1][2][3][4][5]. Because these various and versatile allotropes produce materials with a large range of properties, carbon materials can be used in a number of technological processes, including high-tech catalytic ones [6][7][8][9][10].In heterogeneous catalysis, carbon material plays wellestablished and important roles in a wide range of applications, both as catalyst in its own right and as a unique support material [11][12][13][14][15]. The chemical stability of carbon supports in some specifically aqueous phase biomass conversion surpasses that of metal oxide materials; in addition, carbon materials present other common and key advantages as support materials for catalysis [1,5]. From the point of physical structure, porous carbon can be prepared in different forms (granules, cloth, fibers, pallets, etc.). Due to its chemical properties, carbon structure is resistant to both acidic and basic media. The structure of carbon is stable at high temperature (even above 1023 K under inert atmosphere). The hydrophilic/ hydrophobic nature of carbon can be easily modified. Active metals on the support can be easily reduced. For the purposes of industrial economy and environment, the active phase can be easily recovered. Conventional carbon supports are lower-cost and more easily available than other conventional supports. Although several kinds of carbon materials have been studied, active carbon (AC) [12,[16][17][18][19] and, to a lesser extend, carbon black [20][21][22][23] have long been the most commonly used carbon supports. AC is an amorphous solid prepa...

Modified Nanocarbons for Catalysis

“…Starting to consider the immobilization of metal NPs, the peculiar features of graphene and its derivatives could allow obtaining metal NPs with a high exposed surface area and reduce the diffusion limitations of reagents and products. However, the scarce interaction between metal NPs and unmodified rGO or GO makes difficult to obtain a good dispersion of metal NPs on their surface and paves the way to possible metal leaching and agglomeration processes that could bring to very large metal agglomerates, which may affect the catalytic performance of the final material . Therefore, big efforts have been made for the chemical modification of graphene‐based supports with proper metal stabilizers with the aim to overcome the above‐mentioned issues.…”

“…However, the scarce interaction between metal NPs and unmodified rGO or GO makes difficult to obtain a good dispersion of metal NPs on their surface and paves the way to possible metal leaching and agglomeration processes that could bring to very large metal agglomerates, which may affect the catalytic performance of the final material. [128] Therefore, big efforts have been made for the chemical modification of graphene-based supports with proper metal stabilizers with the aim to overcome the abovementioned issues. Simultaneously, the possibility of the chemical modification of graphene have been also exploited for the preparation of supported organometallic complexes.…”

In Situ Construction of Ag/TiO2/g-C3N4 Heterojunction Nanocomposite Based on Hierarchical Co-Assembly with Sustainable Hydrogen Evolution

“…With the development of semiconductor photocatalysis [1][2][3][4], semiconductor photocatalysts ushered in a glorious era of the photocatalytic water decomposition of H 2 [5][6][7][8]. Graphitic carbon nitride is currently a prominent semiconductor material that has garnered tremendous attention in academia due to its low cost, environmental friendliness, suitable band structure and impressive physical and chemical stability [9][10][11].…”

Palladium nanoclusters immobilized on defective nanodiamond-graphene core-shell supports for semihydrogenation of phenylacetylene

“…In the present, we will report the semihydrogenation of phenylacetylene over Pd/ND@G under mild conditions. In our previous studies, ND@G composing a nanodiamond core and a defective, ultrathin graphene nanoshell was used to support noble metals and the resulting catalysts exhibited superior catalytic activity in CO oxidation and dehydrogenation of alkanes [21,[28][29][30] . In this work, the ND@G material was firstly used in liquid-phase hydrogenation reaction systems to modify the selectivity of the incorporated Pd nanoclusters through a strong metal-support interaction (SMSI) and to promote stability of the Pd clusters.…”