On the Interaction of Metal Nanoparticles with Supports

Major Advances and Challenges in Heterogeneous Catalysis for Environmental Applications: A Review

“…They are embedded between the catalytically active sites of iron particles. The oxides of calcium form a framework, which prevents the catalyst from sintering at higher temperature [59] or even at moderate temperature [60]. The level of sintering is normally affected by the surface chemistry, demonstrating that besides the universally assumed Ostwald ripening, also other routes related with metal surface diffusion can be blamed for the nanoparticle size growth (for example: the synthesis method, the size and shape of the nanoparticles, catalysis dispersion on the support (the distance between the particles), or pre-treatment of the support and reaction environment).…”

“…Additionally to the deterioration in metal dispersion, carbon supports can show chemical instability causing their partial destruction in the proximity of the nanoparticles both in oxidizing and reducing environments at high temperatures. Moreover, Kordas et al [60] evaluated the possible events affecting metal sintering and damaging of the supports using transmission electron microscopy (TEM) analysis. Another study that presents visual examples of the sintering process of nano-scale systems (monitored ex situ, in situ, and under operando conditions) was published by Behafarid and Cuenya [61].…”

Microfluidic Synthesis Enables Dense and Uniform Loading of Surfactant‐Free PtSn Nanocrystals on Carbon Supports for Enhanced Ethanol Oxidation

“…Figure 1d isplays the capillary microfluidic system used to directly grow ultrafine PtSn NPs on carbon spheres.T he reaction solution containing carbon black particles and precursor metal ions is pressurized in ac hamber using pressure-regulated nitrogen gas to flow reaction mixture into the capillary tube reactor. [36] Within roughly 10 s, the reaction solution is able to flow through the capillary tube reactor (with al ength of 1.3 m, including ah eating region of 1.2 ma nd ac ooling region of 0.1 m) to the outlet, where the products are collected. Once the reaction solution flows to the heating region, where the capillary tube is maintained at an elevated temperature,t he reaction solution in the tube can be quickly heated to the desired temperature within av ery short time [35] because of the rapid heat transfer in the thin capillary tube wall and the small volume of solution in the capillary tube.T he fast increase of reaction temperature to ac onstant value leads to ah igh reduction rate of H 2 PtCl 6 and SnCl 4 precursors,a chieving supersaturated concentrations of metal atoms in avery short reaction time.T he supersaturated Pt and Sn atoms nucleate on the surface of the carbon spheres in aw ell-dispersed fashion because heterogeneous nucleation is kinetically preferable compared to homogeneous nucleation.…”

“…Carbon supports were activated by soaking in an aqueous solution of HNO 3 ,l eading to formation of carboxyl groups by oxidation of surface carbon atoms.S urface carboxyl groups provide nucleation sites for formation of PtSn nanocrystals because of strong coordinative interactions between PtSn atoms and carboxyl groups. [36] Within roughly 10 s, the reaction solution is able to flow through the capillary tube reactor (with al ength of 1.3 m, including ah eating region of 1.2 ma nd ac ooling region of 0.1 m) to the outlet, where the products are collected. When the reaction solution flows from the heating region to the cooling region, ad rop in temperature leads to quick cessation of precursor reduction, as well as possible sintering of PtSn NPs.Since the carbon black spheres are well-dispersed in ethylene glycol, the corresponding carbon spheres loaded with PtSn NPs are also well-dispersed.…”

Microfluidic Synthesis Enables Dense and Uniform Loading of Surfactant‐Free PtSn Nanocrystals on Carbon Supports for Enhanced Ethanol Oxidation

“…Carbon supports were activated by soaking in an aqueous solution of HNO 3 , leading to formation of carboxyl groups by oxidation of surface carbon atoms. Surface carboxyl groups provide nucleation sites for formation of PtSn nanocrystals because of strong coordinative interactions between PtSn atoms and carboxyl groups . Within roughly 10 s, the reaction solution is able to flow through the capillary tube reactor (with a length of 1.3 m, including a heating region of 1.2 m and a cooling region of 0.1 m) to the outlet, where the products are collected.…”