Influence of the Method of Preparation of the Pd-Bi/Al2O3 Catalyst on Catalytic Properties in the Reaction of Liquid-Phase Oxidation of Glucose into Gluconic Acid

Role of Bi Adatoms in Bi@Pd Nanoparticles for Electrochemical CO2 Reduction

Surface modification of Pd by foreign metals is an appealing approach to achieve electrochemical CO2 reduction to formate (CO2RR-formate) with an overpotential close to zero. However, the exact role of surface dopants is still under debate. Here, we provide direct experimental proof that Bi adatoms on Pd nanoparticle surface are electrochemically active and geometrically assist electrochemical CO2RR, by utilizing element-selective in situ X-ray absorption spectroscopy (XAS), which reveals that the partly oxidized Bi adatoms as prepared are fully reduced and form a surface single-atom coordinated only with Pd nanoparticles at 0 VRHE, and are oxidized to Bi3+ valence state at 1.1 VRHE. Electrochemical measurements show that the onset potential of the formate formation for Bi@Pd/C (0.05 VRHE) is 0.1 V higher than that of Pd/C (-0.05 VRHE), with the local concentration of formate at -0.15 VRHE increasing from 1.6 to 4.6 mM. An oxygenated species chemisorbed on the Bi adatoms during CO2RR is identified by operando XAS and DFT calculations and is tentatively attributed to an active HC(O*-Bi)2 intermediate with direct Bi-O bonds. Our results clarify the long-term mysterious role of Bi adatoms in the CO2RR process.

Production of gluconic acid from the washed rice waste water using Au/MgO catalyst - A sustainable route

The majority of the waste produced by the food and agriculture industries is abundant in proteins, carbohydrates, and fats, which can be utilized effectively in other food products or industrial products. Especially, washed rice water (WRW) contains a significant quantity of starch that has been discarded without being utilized properly. In the present investigation, we have successfully upgraded washed rice water into the industrially important intermediate, i.e., gluconic acid, using an Au/MgO catalyst in a single pot reaction. The upgrading strategy was developed in three consecutive phases using two different model reactions: (1) glucose to gluconic acid, (2) hydrolysis of starch into glucose, followed by the oxidation reaction. The results showed that almost 60% gluconic acid was achieved at room temperature with atmospheric pressure. The present investigation highlighted that hydrolysis, followed by oxidation reaction is the most promising route for upgrading WRW to gluconic acid.

Chemocatalytic value addition of glucose without carbon-carbon bond cleavage/formation reactions: an overview

As the monomeric unit of the abundant biopolymer cellulose, glucose is considered a sustainable feedstock for producing carbon-based transportation fuels, chemicals, and polymers. The chemocatalytic value addition of glucose can be broadly classified into those involving C-C bond cleavage/formation reactions and those without. The C6 products obtained from glucose are particularly satisfying because their syntheses enjoy a 100% carbon economy. Although multiple derivatives of glucose retaining all six carbon atoms in their moiety are well-documented, they are somewhat dispersed in the literature and never delineated coherently from the perspective of their carbon skeleton. The glucose-derived chemical intermediates discussed in this review include polyols like sorbitol and sorbitan, diols like isosorbide, furanic compounds like 5-(hydroxymethyl)furfural, and carboxylic acids like gluconic acid. Recent advances in producing the intermediates mentioned above from glucose following chemocatalytic routes have been elaborated, and their derivative chemistry highlighted. This review aims to comprehensively understand the prospects and challenges associated with the catalytic synthesis of C6 molecules from glucose.

Novel Blue-Wavelength-Blocking Contact Lens with Er3+/TiO2 NPs: Manufacture and Characterization

Thermally stable titanium dioxide nanoparticles (TiO₂ NPs) doped with erbium ions (Er³⁺) are characterized by uniformity, low excitation energy, and high surface area. The impregnation methodology was used to enhance the optical properties of TiO₂ NPs impregnated with various Er³⁺ ion contents. The synthesized Er³⁺/TiO₂ samples were characterized by energy dispersive X-ray (EDX), metal mapping, UV–Visible spectrum, field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). The Er³⁺ ions, per our findings, were well-distributed on the TiO₂ surface of the anatase phase and there was an insignificant difference in particle size, but there was no change in the particle shapes of the Er³⁺/TiO₂ NPs structure. The maximum band gap degradation occurred with 1.8 wt % of Er³⁺/TiO₂, where the energy gap degraded from 3.13 to 2.63 eV for intrinsic TiO₂. The synthesized Er³⁺/TiO₂ samples possess predominantly finely dispersed erbium ion species on the surface. Er³⁺ ions agglomeration on the surface increased with increasing ions in each sample. We found that 0.6 wt/vol % of Er⁺³/TiO₂ is the best optical coating and produced satisfying results in terms of blocking the transmittance of blue wavelength without reducing the image quality.

Influence of the Pd : Bi ratio on Pd-Bi/Al2O3 catalysts: structure, surface and activity in glucose oxidation

Pd-Bi nanoparticles show high efficiency in catalyzing gluconic acid production by the glucose oxidation reaction. Although this type of catalyst was studied for some time, the correlation between bismuth content and catalytic activity is still unclear. Moreover, there is little information on the principles of the formation of Pd-Bi nanoparticles. In this work, the relation between bismuth content and the activity and selectivity of the PdxBiy/Al2O3 catalyst in the glucose oxidation process was studied. The catalytic samples were prepared by co-impregnation of the alumina support utilizing the metal-organic precursors of Pd and Bi. The samples obtained were tested in the glucose oxidation reaction and were studied by transmission electron microscopy (TEM), X-ray fluorescence analysis, X-ray photoelectron spectroscopy (XPS), and BET adsorption. It has been found that the Pd3 : Bi1 atomic ratio grants the highest catalytic efficiency for the studied samples. To explain this, we predicted stable Pd-Bi nanoparticles using ab initio evolutionary algorithm USPEX. The calculations demonstrate that nanoparticles tend to form Pd(core)-Bi(shell) structures turning to a crown-jewel morphology at lower Bi concentration, thus exposing the active Pd centers while maintaining the promoting effect of Bi.

Effects of external parameters and mass-transfer on the glucose oxidation process catalyzed by Pd–Bi/Al2O3

This work describes the effect of reaction parameters on glucose oxidation in the presence of a Pd3 : Bi1/Al2O3 catalyst.