Monitoring in situ the colloidal synthesis of AuRh/TiO₂ selective-hydrogenation nanocatalysts

Abstract

AuRh nanoparticles (NPs) of various compositions and sizes in the 2-4 nm range were synthesized using a colloidal approach and were characterized at each preparation step by dynamic light scattering (DLS), ultraviolet-visible (UV-vis) spectroscopy, and liquid-phase transmission electron microscopy (liquid TEM).The AuRh colloids appear relatively instable, leading to their gradual coalescence. After fast immobilization of the metallic nanoparticles on rutile TiO 2 nanorods, the materials were investigated by high-resolution transmission electron microscopy (HRTEM) and low-temperature CO adsorption monitored by Fourier transform infrared (FTIR) spectroscopy. The inherent lack of miscibility between Au and Rh leads to partial segregation inside the NPs, which is further exalted after a reducing thermal treatment applied for PVA removal. The catalytic properties in the liquid-phase selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde are strongly influenced by these nanostructural modifications. While in as-prepared samples the intermixing between Au and Rh phases promotes the catalytic performances for Rh-rich AuRh catalysts through Au-induced stabilization of Rh in its metallic form, segregation into Janus particles after reduction decreases the catalytic activity.Bimetallic nanoparticles are of prominent importance in heterogeneous catalysis since the choices of metals and compositions allow one to tune the catalyst selectivity and improve its activity and stability.

Restructuring effects of the chemical environment in metal nanocatalysis and single-atom catalysis

“…This includes electrocatalytic conditions[68][69][70] though there exists limitations due to the strong interaction of the electron beam with the electrochemical medium[71].…”

Donut Assembly of Nanoparticles with High Catalytic Efficiency for Hydrogen Gas Generation from Ammonia Borane

“…Initial evaluation of CP1À Au revealed only minimal activity in AB decomposition in methanol, and we then proceeded to evaluate bimetallic system through incorporation of another metal elements into this soluble NP assembly to improve the catalytic activity. Although it was known that the Au/Rh systems were bulk-immiscible, [31][32][33][34] the segregated bimetallic Au/Rh particles still showed improved catalytic activity compared to pure Au or Rh NPs in some reactions. [35][36][37] Encouraged by that, we expected that incorporation of Rh elements in the assembly could enhance the catalytic activity in AB decomposition.…”

Producing of cinnamyl alcohol from cinnamaldehyde over supported gold nanocatalyst

“…Supported gold nanoparticles (NPs) have attracted intensive attentions recently because of their high selectivity in various redox reactions under moderate reaction conditions [10][11][12]. In previous works, the gold catalysts exhibited potential high selectivity in the selective hydrogenation of unsaturated ketones and aldehydes, which is comparatively superior to other supported noble metal catalysts [13,14]. The performances of the gold catalysts were largely affected by the steric and electronic effects [15][16][17] caused by the size and morphology of gold particles [18][19][20] and the addictive elements [21][22][23].…”