Metal cluster-deposited graphene as an adsorptive material for m-xylene

Abstract

Tetramer clusters of platinum (Pt), palladium (Pd), gold (Au) and silver (Ag) deposited on pristine and defective graphenes were studied as potential adsorptive materials for m-xylene using density functional theory (DFT) calculations including van der Waals contributions to the Hamiltonian. Structural, energetic and electronic (i.e. d-band center, partial density of state and explicit charge) properties have been investigated for understanding the m-xylene adsorption process. The m-xylene adsorption capability in these materials has been compared. The calculation results revealed that Pt4-and Pd4-DG adsorb m-xylene via chemisorption process, while Au4-and Ag4-DG adsorb m-xylene via physisorption. These insights are valuable for applying and developing carbon-based materials in volatile organic compounds (VOC) removal applications, since physisorption-driven materials are suitable as sorbents while their chemisorption 2 counterparts are suitable as catalysts in an oxidation reaction. Those properties in turn can be tuned by modulating the metal adsorption on the carbon-based materials.Fax: +66(0)2564 6985; Tel. +66(0)2564 6705 IntroductionVolatile organic compounds (VOCs) are toxic and odorous 1-3 and photochemical reactions between VOCs and other pollutants originate toxic products and photochemical smog. They are released from various sources including automobiles, refineries, petrochemical units, chemical plants, etc. 2, 4, 5 Many abatement techniques such as combustion, adsorption, bio-filtration, bio degradation and catalytic oxidation have been used for removing VOCs. Activated carbons (ACs), zeolites, metal organic frameworks (MOFs) and metal-doped metal oxides have been extensively explored in this field of research. 4, 6-10 In industry, ACs have been widely used as adsorbents for removing large amount of VOCs in the primary step, since they are relatively inexpensive, large surface area, a variety of pore sizes and reusability. 11, 12 However, some amounts of VOCs are still leaked. Nowadays, improvement of the VOC abatement technology is still challenging, particularly at trace amounts of VOCs.Surface modification and deposition of noble and transition metals have been proposed for enhancing the VOC treatment efficiency in ACs. [13][14][15][16] From the past, the adsorption of aromatic compounds on surfaces of noble-and transition metals have been broadly explored. adsorption of aromatic on metal clusters have been determined by theoretical works. 20, 21 The interactions between aromatic compounds and those metals depend on the nature of the metal.Although many metals exhibit good adsorptive and catalytic properties, they are usually expensive and their wide deployment may not be cost effective. In metal-carbon composites, good adsorptive and catalytic properties are attained by metals, while large surface areas and relatively competitive costs are provided by carbon supports.Among VOCs, xylene is one of the more hazardous aromatic substances found in polluted air. Three isomers of xylene (i.e. m-xylene...

Water at the Interface Between Defective Graphene and Cu or Pt (111) Surfaces

“…For example, the CO oxidation barrier and O 2 dissociation activation energy on Pt are reduced when the metal nanoparticles are supported on defective graphene. More generally, graphene containing defects can be used as supporting material in hydrogen storage devices , and for the adsorption of air pollutants . Carbon vacancy defects are naturally formed during the crystal growth process (particularly in low-temperature growth) but also can be generated on purpose through particle irradiations or chemical treatments. , Notably, vacancy formation energy in G is much lower in the presence of metal adatoms …”

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“…Moreover, defective graphene is also promising in the fields of hydrogen storage 39 , 40 and air purification. 41 Recent theoretical study shows that vacancy defects can highly enhance the binding between graphene and metal surfaces (Cu and Pt) by forming strong organometallic bonds. 42 Therefore, defects may have a big influence on the graphene/TiO 2 interface and thus affect the performance of TiO 2 –graphene nanocomposites.…”

“…The CO oxidation barrier and O 2 dissociation activation energy on small platinum nanoparticles are reduced when the platinum nanoparticles are supported on defective graphene. Moreover, defective graphene is also promising in the fields of hydrogen storage , and air purification . Recent theoretical study shows that vacancy defects can highly enhance the binding between graphene and metal surfaces (Cu and Pt) by forming strong organometallic bonds .…”