Dense Decorate of sub-5nm Au NPs

"Formation of gold nanoparticles supported on carbon nanotubes by using an electroless plating method"

Ma, X.; Lun, N.; Wen, S. Diam. Relat. Mater. 2005, 14, 68-73.
doi:10.1016/j.diamond.2004.07.002

Points:
"Electroless plating with gold on CNTs cannot be succeeded without any activation of the surfaces."


"Pd/Sn catalyticnuclei in a Sn colloidal layer were first introduced onto the surfaces of the oxidized CNTs; after being washed with HCland distilled water, the Sn protective layer was preferentially dissolved and the Pd catalytic nuclei were exposed to agreater extent. In the following step of electroless plating,the individual Pd catalytic centers deposited on the surface of CNTs would reduce gold ions to neutral gold atoms and formed homogeneous dispersed and high-density nucleation centers of gold islands."

Materials: Au-MWNT

Synthesis:
Electroless Plating:

• KBH4 as the active reducing agent.
• MWNT (CVD from acetylene, H2SO4/HNO3, 140 C, 6h) was sonicated in activation solution (SnCl2/PdCl2/HCl, detailed preparation described), washed with 1M HCl/water repeatedly, and stirred in the plating bath for ~15 min at 25C.
• The plating is highly sensitive to the parameters (temp, conc, pH). The reagents should be added in due course.

Characterization:

• TEM
• EDX

Properties:
Size: 3-4 nm (TEM)
Stability: stable against repeated washing and sonication

Speculated Application:
Catalysis

Enhancing MWNT Hydrogen Storage via V/Pd Decoration

"Enhancement of hydrogen storage capacity of carbon nanotubesvia spill-over from vanadium and palladium nanoparticles"

Zacharia, R.; Kim, K. Y.; Kibria, A. K. M. F.; Nahm, K. S. Chem. Phys. Lett. 2005, 412, 369-375.
doi:10.1016/j.cplett.2005.07.020

"The increased hydrogen storage capacity of transition metal-doped carbon nanostructures is attributed to the initial hydrogen adsorption by metal nanoparticles which subsequently dissociate the hydrogen molecules and spill them over to carbon nanotubes."

Materials: V-MWNT; Pd-MWNT

Synthesis:
Electroless:
100 mg MWNTs (CVD from acetylene, purified) and 3 mg PdCl2 were sonicated in acetone for 12 h. Pd2+/Pd: +0.951V (vs SHE).
Reduction-H2:
100 mg MWNTs and 5 mg VCl3 were sonicated for 12 h. Reduced by hydrogen at 250C for 2h.

Characterization:
TEM (Likely incorrect assignments)
Raman
Hydrogen adsorption:

• Sieverts volumetric apparatus: 100 mg CNT; 6h 400C 10(-4) degassing; 2MPa H2.



• V-MWNT (0.69wt%) = Pd-MWNT (0.66) > purified MWNT (0.53) > as-produced (0.31)



• More than half of the hydrogen adsorbed might be attributed to carbon phase



• Desorption: more reversible for V-MWNT than Pd-MWNT at r.t.

Applications:
Hydrogen Storage