Conformal deposition of Pt-dots arrays on polyhedral Pd nanocrystals can enhance Pt catalytic properties and reduce its loading. Herein, a simple method for the fabrication of Pd@Pt core–shell nanodot arrays (Pd@PtNAs) heterostructures via reducing H2PtCl6 and Na2PdCl4 by l-ascorbic acid in an aqueous solution with cetylpyridinium chloride and KBr is reported. The Pt nanodots arrays with a small size (about 3 nm in diameter) were dispersed on the surface of Pd decahedra. Such ultrasmall size Pt dots arrays can effectively increase the proportion of low-coordination Pt atoms. Compared with commercially available Pt/C catalysts, the Pd@PtNAs show obvious improvement in catalytic performance applied to oxygen reduction reaction. The mass activity (0.20 A/mgPt) of the obtained Pd@PtNAs with 36.9 wt % Pt shows 2.2 times relative to Pt/C catalyst (0.09 A/mgPt) for ORR. What’s more, the Pd@PtNAs with 36.9 wt % Pt exhibited highly stable property and mass activity with only 11% loss after 10 000 testing cycle.
Highly dispersed palladium nanoparticles (NPs) supported on UiO-66 as catalyst for CO 2 methanation were prepared by supercritical fluid deposition (SFD). As a result, the most suitable Pd precursor salt and co-solvent are Na 2 PdCl 4 and ethanol/DMF, respectively. The best SFD process condition to deposit the Pd precursor on UiO-66 is 40 °C, 10 MPa and 2 h. Under the above condition, 4% Pd/UiO-66 exhibits the highest activity with 53% of CO 2 conversion and 95% of CH 4 selectivity while the turnover frequency (TOF) value is 3669.4 h −1 . The catalysts were characterized by XRD, BET, TEM, XPS, TGA, CO-DRIFTS and ICP-OES to investigate the structure–activity relationship. The 4% Pd/UiO-66 with the average size of 2.2 nm of Pd prepared in assistance of supercritical fluid behaved the similar activity as the 6%Pd/UiO-66 with average size of 9.7 nm of Pd prepared by sol–gel method. It is showed prospect of technique for reducing noble metal loading resulting from high dispersion effect.
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