Room Temperature Electron Reduction Research Articles

Highly effective Pt-Pd/ZSM-22 catalysts prepared by the room temperature electron reduction method for the n-hexadecane hydroisomerization

The development of highly effective bifunctional catalysts for n-hexadecane hydroisomerization is still essential to produce second-generation biodiesel. Herein, a Pt-Pd/ZSM-22-G (abbreviated as Pt-Pd/Z22-G) bimetallic catalyst was prepared by employing a room temperature electron reduction (RTER) method with glow discharge as the electron source. As a contrast, a series of Pt/Z22-H, Pd/Z22-H and Pt-Pd/Z22-H catalysts were prepared by the conventional hydrogen reduction method. The Pt-Pd/Z22-G catalyst reveals more exposed metal sites, larger CMe/CH+ values and an enhanced distribution of Pt-Pd(111) facets compared with the Pt/Z22-H, Pd/Z22-H and Pt-Pd/Z22-H catalysts. These modifications are originated from the stronger electron interactions and the smaller metal nanoparticles because of the effects of highly energetic reducing electrons. The n-hexadecane hydroisomerization results show that the iso-hexadecane yield over the Pt-Pd/Z22-G catalyst is 82.9%, which is the highest among four investigated catalysts in this work. This phenomenon occurs because more exposed Pt-Pd(111) facets and larger CMe/CH+ ratios are beneficial for the adsorption and hydrogenation of iso-alkene intermediates at metal sites to increase the iso-alkanes yield based on density functional theory (DFT) calculations. Furthermore, the iso-alkanes yield over the Pt-Pd/Z22-G catalyst also keeps steady after long-term tests for 120 h because of the limited metal aggregation and carbon deposition.

The hydroisomerization of n-hexane over highly selective Pd/ZSM-22 bifunctional catalysts: The improvements of metal-acid balance by room temperature electron reduction method

The preparation of bifunctional catalysts with high catalytic selectivity and stability for the n-alkanes hydroisomerization still remains challenging for the production of clean fuel. Herein, two series of Pd/ZSM-22 bifunctional catalysts are prepared by the room temperature electron reduction (Pd/Z22(x)-E) and conventional hydrogen reduction methods (Pd/Z22(x)-C), respectively. The physico-chemical property and catalytic performance for the n-hexane hydroisomerization over all catalysts are studied. Owing to the avoidance of high temperature measurement in the preparation process, the deposited Pd nanoparticles of Pd/Z22(x)-E catalysts reveal higher dispersion, smaller size and larger {1 1 1} facets fraction compared with Pd/Z22(x)-C catalysts. The results of n-hexane hydroisomerization demonstrate that Pd/Z22(x)-E catalysts show promoted catalytic performance because of the stronger metal function and more favourable metal–acid balance. Especially for the Pd/Z22(90)-E catalyst, the maximum i-hexane yield is 76.3% at the n-hexane conversion of 83.9%, which is 8.3% higher than that of the Pd/Z22(90)-C catalyst. In addition, the products distribution and calculated thermodynamic equilibrium constants suggest that the modified characteristics of Pd/Z22(90)-E catalysts are beneficial for both the generation of mono-branched i-hexane products and the limitation of their further isomerization and cracking. Furthermore, the results of long-term tests of 72 h indicate that the Pd/Z22(90)-E catalyst shows enhanced stability due to the weaker Pd aggregation and less carbon deposition. Therefore, the room temperature electron reduction method is an effective way to prepare bifunctional catalysts with improved catalytic performance for n-alkane hydroisomerization.

Preparation of silver nanoparticles in the presence of polyoxometalates

The mechanisms of reduction of silver ions and subsequently oxidation of silver atoms in the presence of polyoxometalates (POMs) are discussed. A step-by-step room temperature electron reduction of silver ions and its subsequent reactions has been used in this work to monitor oxidation of silver atoms and its clusters. The silver atoms can transfer electron to POMs is revealed by decrease in the yield of silver clusters and increase in their decay rates. The results of continuous γ-irradiation are compared using UV–visible (UV–Vis) absorption spectra, underlying the effect of silver atoms accumulation in the absence of POMs. Silver nanoparticles (Ag NPs) prepared by reduced silicotungstic acid (STA) were used as Raman substrate and also for antibacterial studies against panel of human pathogenic bacteria. The Ag NPs exhibited antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens evaluated by well diffusion assay. The inhibition zones were within the range of 10 to 14 mm. We have also explored the surface enhanced Raman scattering (SERS) activity of the Ag NPs substrates using 1.0 × 10−7 M solution of crystal violet (CV) as Raman probe molecule. It was possible to detect SERS spectral pattern of CV on Ag NPs substrate with a high signal-to-noise ratio. Both SERS and antibacterial studies show that this simple, low cost, and greener method for synthesizing Ag NPs may be valuable in future studies about SERS sensor development and bio-applications.

L-Phenylalanine-Templated Platinum Catalyst with Enhanced Performance for Oxygen Reduction Reaction.

Pt-based materials are the most efficient catalysts for the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. However, fabrication of active and stable Pt catalysts still remains challenging. In this work, Pt-l-phenylalanine (Pt-LPHE) films, with highly dispersed Pt nanoparticles (NPs) featuring predominately (111) facets, have been prepared via a room-temperature electron reduction method. Loading Pt-LPHE onto carbon support produces a novel nanomaterial (Pt-AL/C), resulting in a simultaneous loading of highly dispersed Pt NPs and N doping. Density functional theory calculations demonstrate that the N dopants stabilize the Pt NPs and reduce the *O/*OH binding energies on the Pt NPs. As a result, the Pt-AL/C nanomaterial shows significantly enhanced ORR activity and stability over commercial Pt/C after 10 000 cycle stability tests. This work provides a novel eco-friendly and energy-neutral approach for preparing metal NPs with controllable structures and sizes.

Enhanced hydrogen production from water on Pt/g-C3N4 by room temperature electron reduction

An efficient Pt/g-C3N4 photocatalyst was prepared via glow discharge plasma reduction. Based on the hydrogen evolution from water splitting under visible light irradiation, the Pt/g-C3N4 obtained through plasma reduction exhibited enhanced photocatalytic performance with a H2 evolution rate of 33.9 μmol/h. Among the samples obtained through plasma reduction under different environments, the Pt/g-C3N4 photocatalyst with Pt reduced in NaOH alkaline environment exhibited a markedly increased H2 evolution rate of 40 μmol/h. The enhanced photocatalytic performance could be attributed to plasma reduction controlling the size of Pt particles and the alkaline environment promoting Pt reduction.

Highly Active and Stable Pt-Pd Alloy Catalysts Synthesized by Room-Temperature Electron Reduction for Oxygen Reduction Reaction.

Carbon‐supported platinum (Pt) and palladium (Pd) alloy catalyst has become a promising alternative electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. In this work, the synthesis of highly active and stable carbon‐supported Pt–Pd alloy catalysts is reported with a room‐temperature electron reduction method. The alloy nanoparticles thus prepared show a particle size around 2.6 nm and a core–shell structure with Pt as the shell. With this structure, the breaking of O–O bands and desorption of OH are both promoted in electrocatalysis of ORR. In comparison with the commercial Pt/C catalyst prepared by conventional method, the mass activity of the Pt–Pd/C catalyst for ORR is shown to increase by a factor of ≈4. After 10 000‐cycle durability test, the Pt–Pd/C catalyst is shown to retain 96.5% of the mass activity, which is much more stable than that of the commercial Pt/C catalyst.

The room temperature electron reduction for the preparation of silver nanoparticles on cotton with high antimicrobial activity

Functionalization of cotton by fabricating Ag nanoparticles (NPs) on cotton surface has aroused great interest for its promising applications for chemical, electronic, photonic and many other devices. Herein, a simple and rapid room temperature electron reduction, which uses argon glow discharge as the electron source, was employed to fabricate Ag NPs on cotton without using any chemical reducing agent. The color of Ag NP loaded cotton changes from light yellow to black upon the increasing Ag loading amount, while the average size of Ag NPs on the cotton barely changes from 4.4 to 6.3nm. This indicates the color change is due to the size of Ag aggregates rather than the size of single Ag NP, as demonstrated by scanning electron microscope (SEM) and UV–vis absorption analyses. The functionalized fabric exhibits high antimicrobial activity against both Gram-negative bacterium E. coli and Gram-positive bacterium B. subtilis.

Characterization and Application of Au Nanoparticle/Agarose Composite Film Fabricated by Room Temperature Electron Reduction

Characterization and Application of Au Nanoparticle/Agarose Composite Film Fabricated by Room Temperature Electron Reduction

Preparation of Floating Au/PVP Film on Water for a Green and Rapid Extraction of Gold Ion

Currently, the demand for gold is ever increasing while the reserve of gold ore is very limited. The extraction of gold ion from various waste effluents is now a very important way for a sustainable gold supply. In this work, a green, selective, simple, easy, cheap and energy efficient way to recover Au ion from a mimic waste stream containing Au, Zn, Fe and Cu ions has been developed using a room temperature electron reduction with argon glow discharge as the electron source. Metal ions with sufficiently high standard electrode potentials can be reduced by such electron reduction. A selective reduction of gold ion has been thereby established, where other metal ions remain in the solution. With the addition of poly(vinylpyrrolidone) (PVP), an Au/PVP floating film is rapidly formed on the surface of water within a few minutes. This makes the collection of the recovered gold very easy with very high recovery yield. The gold recovery yield reaches 87.19% in 60 s and 99.96% in 480 s under the reaction condit...

Highly active and stable Pt (111) catalysts synthesized by peptide assisted room temperature electron reduction for oxygen reduction reaction

While carbon supported platinum (Pt) catalyst is the most effective and widely used cathode catalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells, the preparation of active and stable Pt catalysts remains challenging. In this work, we report a room temperature electron reduction method for the synthesis of a highly active and stable carbon supported Pt (111) catalyst under peptide assistance (Pt (111)-P/C). Such prepared catalyst shows surface sites featuring predominately (111) facets with particle size around 2nm. In comparison with commercial Pt/C catalyst prepared by conventional methods, the mass activity and specific activity of the Pt (111)-P/C catalyst for ORR are shown to increase by a factor of ~2. A 10,000-cycle durability test of the Pt (111)-P/C catalyst has also showed a significantly enhanced stability over the commercial Pt/C catalyst.

Floating silver film: A flexible surface-enhanced Raman spectroscopy substrate for direct liquid phase detection at gas–liquid interfaces

In recent years, surface-enhanced Raman spectroscopy (SERS) has developed rapidly and is used for the detection of molecules and biomolecules in liquids. However, few studies have focused on SERS using a water surface as the substrate. A floating metal film on water is desirable for an enhanced SERS performance. In this work, silver nanoparticles (Ag NPs) encased in poly(vinylpyrrolidone) films (Ag-PVP films) were synthesized on the surface of an aqueous solution by room temperature electron reduction. A floating silver film on a water surface was thereby achieved and is reported for the first time. The synthesized Ag-PVP film is an excellent flexible substrate for SERS and has other potential applications. Using the floating silver film as a flexible SERS substrate, 10–11 M of 4-aminothiophenol, 10–6 M of riboflavin, 10–9 M of 4-mercaptobenzoic acid, 10–7 M of 4-mercaptophenol, and 10–7 M of 4-aminobenzoic acid are identified, demonstrating potential use for the floating substrate in the liquid-phase detection of molecules.

Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

ChemInform Abstract: Perspectives on Electron‐Assisted Reduction for Preparation of Highly Dispersed Noble Metal Catalysts

AbstractReview: 45 refs.

Silver nanoparticle aggregates by room temperature electron reduction: preparation and characterization

Silver nanoparticle aggregates were fabricated on AAO substrate via room temperature electron reduction. Their color depends on the size of the aggregate, rather than on the size of single AgNPs.

One-step fabrication of self-assembled peptide thin films with highly dispersed noble metal nanoparticles.

Fabrication of organic thin films with highly dispersed inorganic nanoparticles is a very challenging topic. In this work, a new approach that combines electron-induced molecular self-assembly with simultaneous nanoparticle formation by room temperature electron reduction was developed to prepare peptide thin films with highly dispersed noble metal nanoparticles. Argon glow discharge was employed as the resource of electrons. The peptide motif KLVFF (Aβ16-20) self-assembled into two-dimensional membranes under the influence of hydrated electrons, while the metal ions in solution can be simultaneously reduced by electrons to form nanoparticles. Our TEM imaging reveals that metal nanoparticles were well-distributed in the resulting peptide thin films. Our results also suggest that the size of metal nanoparticles can be tuned by varying the initial concentration of the metal ion. This simple approach can be viewed as a promising strategy to create hybrid thin films that integrate functional inorganics into biomolecule scaffolds.

Perspectives on Electron-Assisted Reduction for Preparation of Highly Dispersed Noble Metal Catalysts

Electrons are the greenest reducing agent for the preparation of highly dispersed noble metal catalysts. Two methods have been developed with electrons as the reducing agent: electron beam irradiation and room-temperature electron reduction with glow discharge or radio frequency discharge as the source of electrons. In this perspective, we attempt to summarize the current status of electron reduction with those non-hydrogen discharges as the electron source. Future developments have been addressed, too. The room-temperature electron reduction via discharges is excellent for size control with fast nucleation and slow crystal growth. It is a simple, easy, cheap, and energy efficient way to reduce metal ions. It is also worthwhile to load noble metal particles into channels of ordered porous materials, like SBA-15, with no need for complex chemical modification. The room-temperature operation makes it very useful for the preparation of noble metal catalysts supported on thermal sensitive substrates like poro...