The Synergetic Effect of Support‐oxygen Groups and Pt Particle Size in the Oxidation of α‐D‐glucose: A Proximity Effect in Adsorption

Abstract

The influence of the support‐oxygen groups and Pt particle size on the catalytic performance of Pt/AC for the aerobic oxidation of α‐D‐glucose to gluconic acid (glycolate) was studied. Surface‐oxygen groups were introduced by treating the activated carbon support with diluted HNO3 without significantly affecting the support porosity. The platinum particle size could be decreased on both the treated and untreated support by adding an additional calcination step to the synthesis. The presence of oxygen‐containing groups is shown to be highly beneficial (∼4 fold increase in the turnover frequency) only for the smallest Pt particle size (1.8–2.5 nm, determined by TEM). For the catalyst with the larger Pt size (3.4–3.6 nm), the presence of additional oxygen‐contacting groups does not significantly enhance the activity. Since the size of the smaller Pt particles is close to the product/substrate molecular diameter (glucose/gluconic acid, ∼0.9 nm) the observed effect can be attributed to the effective repulsion by the negatively charged oxygen groups in close proximity to the glycolate reaction product. The increase in activity originates from the resulting enhanced desorption of glycolate by alleviating the product inhibition presence due to the strong interaction of glycolate with Pt.

Influence of carbon support surface modification on the performance of nickel catalysts in carbon dioxide hydrogenation

“…The formation of CO 2 (Fig. 1A) was attributed to the decomposition of carboxylic acids (100 and 400 • C), anhydrides (200 -600 • C) and lactone groups (400 -900 • C) [25][26][27]51]. CO formation (Fig.…”

“…As a result, it is possible to vary the point of zero charge (PZC) and consequently the acidity or basicity over a wide range. A reflux treatment of pristine carbon (in this case graphite nanoplatelets, GNP) in HNO 3 typically results in the incorporation of carboxylic, lactone and anhydride surface groups [25][26][27], increasing the acidic character of the material. An amination treatment of the oxidized carbon (GNP-O) converts the oxygen-into nitrogen-containing surface groups (GNP-N), which increase the surface basicity [22,23,28].…”

Cinnamaldehyde hydrogenation over carbon supported molybdenum and tungsten carbide catalysts

“…28 The blue triangles indicated the characteristic metallic Pt crystal structure (PDF 88-2343). 32,33 TEM and XRD prove the successful synthesis of Pt and carbide nanoparticles with a particle sizes in a similar range. CO chemisorption was used to establish the number of active sites as it is commonly used for Pt and carbide catalysts.…”

“…28 The blue triangles indicated the characteristic metallic Pt crystal structure (PDF 88-2343). 32,33 TEM and XRD prove the successful synthesis of Pt and carbide nanoparticles with a particle sizes in a similar range.…”

Aqueous Phase Reforming over Platinum Catalysts on Doped Carbon Supports: Exploring Platinum–Heteroatom Interactions

“…Previous studies have shown that electronic effects can either hinder or improve the adsorption of reactants on catalysts containing functional groups on carbon supports. − According to Wang et al, , during the APR of EG over Pt catalysts supported on carbon nanotubes (CNTs), competitive adsorption occurs between the solvent and the reactant. The high polarity of hydrophilic oxygen-containing supports leads to an increase in the local concentration of water around the support, resulting in a decrease in the hydrogen turnover frequency.…”