Hierarchical Carbon Nanotube Membrane-Supported Gold Nanoparticles for Rapid Catalytic Reduction of p-Nitrophenol

Abstract

Gold nanoparticles (AuNPs) have attracted increasing attention as catalysts for pollutant degradation because of their unique reactivity. Direct use of gold nanoparticles in water treatment faces prohibitive challenges from nanoparticle aggregation and post-treatment separation. To prevent nanoparticles from aggregating and eliminate the need for separation, we affixed AuNPs on hierarchical carbon nanotube membrane (HCNM) that was approximately 50 μm thin with 10 μm × 10 μm openings as pores for water passage. HCNM was fabricated by growing vertically aligned carbon nanotube (CNT) arrays on stainless steel mesh. Using p-nitrophenol (PNP) as model pollutant, we showed that in batch experiments HCNM-supported AuNPs retained 78% of their catalytic capability compared to suspended AuNPs. The slight reduction in reactivity was attributed to the blockage of part of the gold surface at the AuNP−CNT juncture. When the membrane was used in continuous flow-through operation, HCNM-supported AuNPs achieved 71% of the maximum catalytic ability measured in batch. The rapid kinetics obtained with HCNM-supported AuNPs was in great contrast to the slow kinetics that one would expect for a rigid membrane of similar configuration. For a rigid membrane, water passing through microscopic pores was confined as laminar flow and thus would not mix well with catalysts affixed on pore walls. For HCNM, CNTs aligning pore walls were flexible so that they could move vigorously to create a chaotic mixing condition and promote AuNP-catalyzed PNP reduction.

Rational design of nanomaterials for water treatment

“…[335][336][337][338][339][340] When operated under pressure-driven convective flow, the active membranes provide reactants rapid access to active sites, thereby minimizing the mass transfer limitations associated with other high surface area-to-volume materials, leading to enhanced treatment performance. [335][336][337][338][339][340] When operated under pressure-driven convective flow, the active membranes provide reactants rapid access to active sites, thereby minimizing the mass transfer limitations associated with other high surface area-to-volume materials, leading to enhanced treatment performance.…”

Gold nanoparticles decorated on Bingel–thiol functionalized multiwall carbon nanotubes as an efficient and robust catalyst

“…A number of AuNP-CNT hybrids have been reported mainly for sensing [19] and more recently, for catalytic applications [20][21][22][23][24][25]. For advanced catalysis strong covalent bonding between the support and AuNP [26] is required in order to obtain stable structures, resistant to successive physical processing during the catalytic and recycling or continuous flow processes.…”

Facile Decoration of Multiwalled Carbon Nanotubes with Hetero-oligophenylene Stabilized-Gold Nanoparticles: Visible Light Photocatalytic Degradation of Rhodamine B Dye

“…Unfortunately, direct use of AuNPs for dye degradation suffers from challenges such as nanoparticle aggregation and posttreatment separation of nanoparticles. 38 Hence, to overcome these problems, we planned to 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 MWCNT@AuNPs nanohybrid, oxidized multiwalled carbon nanotubes and AuNPs solutions were mixed at a 1:1 ratio (3 mL O-MWCNT (1.5 mg/mL) to 3 mL of 5 mM of AuNPs solution).…”