Pt/C nanocatalysts

A well-distributed deposition of Pt/C nanocatalyst and Nafion ionomer on bofh hydrophilic and hydrophobic carbon-based electrodes has been successfully obfained using a Pt/C concentration of 1.0 g/L, an electrical field of 300 V/cm, and a deposition time of 5 minutes [118]. The deposition of Pt/C nanocatalysts and Nafion solution via the electrophoretic process gives rise to higher deposition efficiency and a uniform distribution of catalyst and Nafion ionomer on the PEMFC electrodes. 

Louh, R. R, Huang, H., and Tsai, F. Novel deposition of Pt/C nanocatalysts and Nation solution on carbon-based electrodes via electrophoretic process for PEM fuel cells. Journal of Fuel Cell Science and Technology 2007 4 72-78. 

Prahhuram J, Zhao TS, Wong CW, Guo JW. Synthesis and physical/electrochemical characterization of Pt/C nanocatalyst for polymer electrol5te fuel cells. J Power Sources 2004 134 1-6. 

Hxii CL, Li XG, Hsing IM. Well-dispersed surfactant-stabilized Pt/C nanocatalysts for fuel cell application dispersion control and sxufactant removal. Electrochim Acta 2005 51 711-9. 

It should be mentioned here that Sn sites are not considered to be the solitary source for OHad, which could be adsorbed on Pt sites owing to the influence of adjunct Sn atoms [Stamenkovic et al., 2005], The promotional effect of Sn was later confirmed on a PtSn/C nanocatalyst [Arenz et al., 2005], which exhibits similar behavior that was assigned primarily to the formation of reactive OH species at much lower potential than on pure Pt catalysts. Based on these findings, the bifunctional effect was unambiguously confirmed for Pt-Sn surfaces, where Sn sites serve as a source of oxygenated species that boost CO oxidation at low potentials and allow these surfaces to be employed as CO-tolerant catalysts. 

Godoi DRM, Perez J, Villullas HM (2009) Effects of alloyed and oxide phases on methanol oxidation of Pt — Ru/C nanocatalysts of the same particle size. J Phys Chem C... 

Another promising way to improve the activity and durability of Pd-based nanocatalysts is to deposit a Pt layer on them. Recently, Pd/C and PdM/C catalysts modified by a Pt monolayer were found to possess higher activity than that of Pt/C due to the strain and electronic effects from the Pd-based cores, and the durability of the catalysts is improved significantly and comparable to Pt/C [70, 93-95]. The Pd-based core materials are expected to be partially dissolved xmder the fuel cell operation conditions due to some defects in the Pt monolayer. In the meantime, the diffusion of Pt atoms on the surface results in a more compact shell. Thus, further dissolution of Pd-based core is greatly reduced. 

Figure 4.34. Formic acid oxidation on Pt Pdi. /C nanocatalysts prepared by a surfactant stabilized method using methanol as the redncing agent. 293 K, 50 mV s 0.25 M HCOOH - 0.25 M HCIO4 [172]. (Reproduced from Electrochimica Acta, 51(17), Li X, Hsing 1-M, Electrooxidation of formic acid on carbon snpported Pt Pdi- (x = 0-1) nanocatalysts, 3477-83,2006, with permission from Elsevier.)...

Figure 14.13. High-resolution TEM bright-held images of supported Pt catalysts prepared by SB12-stabilized method (a) Pt/MWNTs-m, (b) Pt/MWNTs-m, (c) Pt/C, and (d) Pt/C [100]. (Reprinted by permission of ECS—The Electrochemical Society, from Li X, Ge S, Hui CL, Hsinga I-M. Well-dispersed multiwalled carbon nanotubes supported platinum nanocatalysts for oxygen reduction.)...

Kim SH, Jung C-H, Sahu N, Park D, Yun JY, Ha H, Park JY (2013) Catalytic activity of Au/ UO2 and Pt/Ti02 nanocatalysts prepared with arc plasma deposition under CO oxidation. Appl Catal Gen 454 53-58... 

The presence of subtle differences in redox potentials and metal lattices of the different base metals in the ternary alloy allows better maneuvering of atoms in the nanoalloy formation and annealing processes than those in the binary counterparts. While this concept is under our investigation, we have demonstrated a number of ternary nanoalloys that outperform their binary counterparts. Examples are shown in Figure 11.15 for several ternary Pt-based nanocatalysts (e.g., PtNiCo/C, PtIrCo/C, PtVFe/C, and PtNiFe/C) [154,155,157,190] in comparison with commercial Pt catalysts for ORR in acidic electrolyte. 

Flectrocatalytic activities of Pt/C and PtRu/C nanocatalysts [63,64], obtained by NaBH4 reduction methods using citric acid as a stabilizing agent, depend on the molar ratio of citric acid to chloroplatinic acid, CA/Pt. The Pt/C obtained with a CA/Pt molar ratio = 2 1 exhibited the greatest MOR current compared to those prepared using other CA/Pt molar ratios. On the other hand, in the case of PtRu/C nanocatalysts, the MOR current was the greatest when the catalyst was prepared with CA/PtRu ratio=1. The activities of these catalysts were... 

FIG U RE 4.13 Comparison of the ORR specific and mass activities derived from the kinetic currents at 0.9 V (vs. RHE) in Figure 4.2 for hollow PtML/Pd2oAu(h)/C nanocatalysts (red, on the right) made using electrode-posited Ni templates and solid Pt/C nanoparticles (blue, on the left) made by electrodeposition. 

Recently, Liew et al. reported the use of chitosan-stabilized Pt and Pd colloidal particles as catalysts for olefin hydrogenation [51]. The nanocatalysts with a diameter ca. 2 nm were produced from PdCl2 and K2PtCl4 upon reduction with sodium borohydride in the presence of chitosan, a commercial biopolymer, under various molar ratios. These colloids were used for the hydrogenation of oct-1-ene and cyclooctene in methanol at atmospheric pressure and 30 °C. The catalytic activities in term of turnover frequency (TOF mol. product mol. metal-1 h-1)... 

Rhee and coworkers published the synthesis of bimetallic Pt-Pd nanoparticles [57] or Pd-Rh nanoparticles [58] within dendrimers as nanoreactors. These nanocatalysts showed a promising catalytic activity in the partial hydrogenation of 1,3-cyclooctadiene. The reaction was carried out in an ethanol/water mixture at 20 °C under dihydrogen at atmospheric pressure. The dendrimer-encapsulated nanoclusters could be reused, without significant loss of activity. 

Zhou W-P, Li M, Koenigsmami C, Ma C, Wong SS, Adzic RR (2011) Morphology-dependent activity of Pt nanocatalysts for ethanol oxidation in acidic media nanowires versus nanoparticles. Electrochim Acta 56(27) 9824—9830... 

Shao Y, Zhang S, Wang C, Me Z, Liu J, Wang Y, Lin Y (2010) Highly durable graphene nanoplatelets supported Pt nanocatalysts for oxygen reduction. J Power Sources 195 4600-4605... 

Fig. 5.14 TEM and thermal stability of Pt/Si0i TL02 nanocatalysts, (a, b) Pt/SiOiOTiOjNPs, (c, d) Pt/Si02 TL02NPs after calcination at 600 °C in air. (e, f) ADF STEM images and corresponding EDS line spectra of a single Pt/Si02 Ti02NPs to prove the existence of the ultrathin Ti02 layer. The bars represent (a, c, e) 10 nm and (b, d) 5 nm. Adapted from ref. [64]...

S. H. Joo, J. Y. Park, C-K. Tsung, Y. Yamada, P. Yang, and G. A. Somoijai, 2009, Thermally stable Pt/mesoporous silica core-shell nanocatalysts for high-temperature reactions. Nature Materials 8, 126-131... 

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