Control of catalytic nanoparticle synthesis: general discussion

Abstract

D´eborah De Masi opened the discussion of the paper by Laura Prati: Can you explain why you have better results with ruthenium nanoparticles than with bimetallic RuAu NPs? Is it due to a change of the crystallinity of Ru when it is on the surface of Au? Laura Prati replied: There is not a direct explanation but we experienced that the synergistic eff ect is not always positive. It depends on the structure, on the electronic distribution, on the matching between reactant, etc. Aldiar Adishev asked: Can you explain how the introduction of gold aff ects reactions tested with bimetallic systems? Or do you have future plans to further study the eff ect of gold? Laura Prati answered: We have seen that Au can have an eff ect on both electronic or geometric eff ects. However the balance between these two factors depends on the structures of the bimetallic particles you are synthesizing. In the case of Pd, for example, we have shown that the eff ect of gold mainly aff ects the O2 interaction with the catalyst thus in turn reducing the occurrence of Pd-O species. Baldassarre Venezia remarked: In this work it has also been emphasized how the Pd/AC and AuPd/AC catalyst were selective in the oxidation of benzyl alcohol to benzaldehyde. However, might this result be due to the low concentration of benzyl alcohol (0.3 M in cyclohexane) employed in the oxidation reaction? The low amount of benzyl alcohol in the autoclave might have hindered the disproportionation reaction of benzyl alcohol into toluene and benzaldehyde, whose kinetics is generally proportional to benzyl alcohol concentration and reaction temperature. Laura Prati responded: Actually we used quite dilute solution (0.3 M). Of course this could have an impact on the selectivity of the reaction. However we established that in the case of AuPd compared to pure Pd there is a decreased adsorption of oxygen on the catalyst surface which can explain a diff erent selectivity. Please refer to previous work in ref. 1 and 2.

Toward Overcoming the Challenges in the Comparison of Different Pd Nanocatalysts: Case Study of the Ethanol Oxidation Reaction

“…To advance our understanding of catalytic systems and rationally develop improved catalysts, a deeper understanding is needed on how the entangled relationships between synthesis, NP size, nature of support, protocol, and testing conditions affects the catalytic properties [36,37]. It is generally important for further understanding and benchmarking to be able to compare the many different materials that are proposed and screened as catalysts to well-established "standard" or "commercially available" catalysts [38].…”

Electrocatalyst Performances in Direct Alcohol Fuel Cells: Defect Engineering Protocols, Electrocatalytic Pathways, Key Parameters for Improvement, and Breakthroughs on the Horizon

“…Comparing different nanomaterials which are proposed and screened as electrocatalysts to commercial and standard catalyst materials is also of great importance; hence, a surfactant-free synthesis method can be used to perform such studies with an example of EOR. [271,272] EOR electrodes were developed by loading Pd on Vulcan (Vx) carbon. After being subjected to chronoamperometry, the nanosized Pd catalysts increased in size.…”

“…Comparing different nanomaterials which are proposed and screened as electrocatalysts to commercial and standard catalyst materials is also of great importance; hence, a surfactant‐free synthesis method can be used to perform such studies with an example of EOR. [ 271,272 ]…”

Platinum Nanoparticle Formation Kinetics and Mechanistic Studies: Evidence for an Alternative 4-Step Mechanism Involving Size-Dependent Growth and Chloride Anion and Room-Dust-Dependent Nucleation

“…Nanoparticles (NPs) composed of Pt, Pd, Ir, Rh, or other transition metals have catalytic, medicinal, energy, and environmental applications that invariably depend on their size, particle size distribution (PSD), and shape. − Platinum NPs (Pt 0 n ) have been extensively studied due to their high catalytic activity compared to bulk Pt 0 metal as well as other applications that range from uses in biotechnology to optoelectronics. − While control over Pt 0 n size and PSD has been probed empirically via the choice of precursor, ligands, temperature, concentration, pressure, reducing agent, and solvent, ,− the majority of reports still rely on trial-and-error based, hence mechanistically unoptimized, syntheses. At present, a more broadly applicable − Pt 0 n NP formation mechanism remains unclear, ,− despite Pt 0 n being an important, widely employed nanomaterial. ,,− Hence, obtaining the underlying mechanism(s) of particle formation process including its nucleation, growth, and any extant aggregation steps remains important and is continued herein for the specific case of Pt 0 n NPs.…”