Engineering Surface Ligands of Noble Metal Nanocatalysts in Tuning the Product Selectivity

Abstract

Nanosized noble metal catalysts supported on high-surface-area support are of great importance for numerous industrial chemical processes to mediate reaction pathways in heterogeneous catalysis. Control of surface area and surface energy of nanocatalysts is a key to achieving high activity and selectivity for desired products. In the past decade, new synthetic methodologies for noble metal nanocatalysts with well-defined nanostructures have been developed. Wet-chemical preparation of noble metal nanocatalysts usually involves the utilization of specific surfactants that can bind the surface of nanocatalysts as ligands to control the nanostructures and prevent the coalescence of nanocatalysts. Surface ligands that form a densely packed self-assembled monolayer offer a facile solution to tune the surface energy of nanocatalysts, and, therefore, the selectivity of products. In this minireview, we highlight the recent advances in understanding the role of surface ligands in control over the product selectivity in a multi-product reaction using noble metal nanocatalysts. The review is outlined according to the three possible roles of surface ligands, including steric effect, orientation effect and surface charge state, in varying the adsorption/binding of reactants/transition states.

In Situ Synthesis of Bi2O3 Nanoparticles on ZincMe (Me=Al or Cr) Layered Double Hydroxide Frameworks for Photocatalytic Oxygen Evolution from Water under Solar‐Light Activation

“…After calcination, the same phenomena were observed for both Bi 2 O 3 /ZnO/ZnAl 2 O 4 and Bi 2 O 3 /ZnO/ZnCr 2 O 4 , for example, a strong absorption in the UV region with a similar band maximum at λ =370 nm and a clear redshift in the visible‐light region. This may be ascribed to the well‐defined excitation band of the evolved oxides . In addition, owing to calcination, the intensity of the absorption of visible light increases along with a redshift in the absorption edges at λ =450 and 690 nm for Bi 2 O 3 NPs/ZnO/ZnAl 2 O 4 and Bi 2 O 3 NPs/ZnO/ZnCr 2 O 4 , respectively, which further supports the hypothesis of the cooperative effects of Bi 2 O 3 NPs/ZnO/ZnAl 2 O 4 and Bi 2 O 3 NPs/ZnO/ZnCr 2 O 4 .…”

“…This may be ascribed to the well-defined excitation band of the evolved oxides. [29] In addition, owing to calcination, the intensity of the absorption of visible light increases along with ar edshift in the absorption edges at l = 450 and 690 nm for Bi 2 [19] Owing to the band-bending process, the changes in the diffuse reflectance absorption spectra after deposition of the nanoparticles are ac onsequence of the absorption characteristics of the de-positedN Ps of the metals/oxides that are superimposed on the (original) spectrum.A sB i 2 O 3 nanoparticles were directly obtained on the larger nanoparticles of the LDHs during the reformation processo ft he LDHs from the mixed oxides, it is difficult to distinctly evidence between manifestationso ft he band-bending and/orb and-gapping processes in the Bi 2 O 3 NPs/LDHs nanocomposites,a nd thus, the band-gap valuesw ere not calculated.…”

Support‐Independent Surface Functionalization for Efficient Pd Loading in Catalytic Hydrogenation

“…For example, Lei et al . reported the role of engineering surface ligands in controlling the nanostructures and preventing the agglomeration of NPs …”

Shape selection through epitaxy of supported platinum nanocrystals

“…It has to be noted that ligands are still present on the surface after washing. While ligands can be beneficial to several catalytic reactions, [38][39][40] structureperformance relationships concerning specific facets would require ligand removal, which should be possible without any coalescence thanks to the robust Pt-Pt interface between the support and the nanostructures which should also prevent easy sintering.…”