Sub-10 nm Platinum Nanocrystals with Size and Shape Control: Catalytic Study for Ethylene and Pyrrole Hydrogenation

Abstract

Platinum nanocubes and nanopolyhedra with tunable size from 5 nm to 9 nm were synthesized by controlling the reducing rate of metal precursor ions in a one-pot polyol synthesis. A two-stage process is proposed for the simultaneous control of size and shape.In the first stage, the oxidation state of the metal ion precursors determined the nucleation rate and consequently the number of nuclei. The reaction temperature controlled the shape in the second stage by regulation of the growth kinetics. These well-defined nanocrystals were loaded into MCF-17 mesoporous silica for examination of catalytic properties. Pt loadings and dispersions of the supported catalysts were determined by elemental analysis (ICP-MS) and H 2 chemisorption isotherms, respectively. Ethylene hydrogenation rates over the Pt nanocrystals were independent of both size and shape and comparable to Pt single crystals. For pyrrole hydrogenation, the nanocubes enhanced ring opening ability and thus showed a higher selectivity to n-butylamine compared to nanopolyhedra.

Nanocatalysis I: Synthesis of Metal and Bimetallic Nanoparticles and Porous Oxides and Their Catalytic Reaction Studies

“…By rational selection of surfactants, reducing agents, and additional foreign metal ions, nucleation and growth kinetics are further regulated to produce nanoparticles with different sizes and shapes [3]. For example, Pt nanocubes were selectively produced when an alkylammonium salt was introduced in the presence of PVP [16]. As shown in Fig.…”

Shape-controlled synthesis of Pt-Ir nanocubes with preferential (100) orientation and their unusual enhanced electrocatalytic activities

“…As a result, great efforts have been devoted to synthesize Pt NPs with controlled shape to tailor their properties such as reactivity and selectivity [11][12][13][14][15]. For example, cubic Pt NPs exposing (100) surfaces have been found to benefit a wide variety of catalytic reactions [17][18][19][20][21][22][23][24]. Solla-Gullón et al [21,22,24] reported that the ammonia electro-oxidation is an extremely structure sensitive reaction (it takes place almost exclusively on Pt (100) sites) and thus the cubic Pt (100) NPs are much more active than polycrystalline Pt or Pt (111) NPs.…”

“…Wang et al [17] found that the current density measured on the Pt nanocubes is much higher than that of the polyhedral or truncated cubic Pt NPs for the oxygen reduction reaction (ORR) in H 2 SO 4 solution. Tsung et al [18] showed that in the case of pyrrole hydrogenation, Pt nanocubes enhanced ring-opening ability and thus showed a higher selectivity to n-butylamine as compared with Pt nanopolyhedra. In addition, it has been reported that the Pt nanocube catalyst with the edge of stepped (100) faces favored the breakage of CH 3 OH and CH 3 CH 2 OH compared with polycrystalline Pt nanocatalyst.…”

Alcohol Oxidation at Platinum–Gas and Platinum–Liquid Interfaces: The Effect of Platinum Nanoparticle Size, Water Coadsorption, and Alcohol Concentration

“…In order to study the catalytic alcohol oxidation reaction with molecular oxygen in the gas and liquid phases, we chose the mesoporous silica MCF-17 as the Pt support. 15,16 MCF-17 has wide pore size ranges from 15 to 50 nm which are adequate to incorporate the sub 10 nm Pt NPs. The amount of Pt loaded into the supports was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES).…”