Size Of Pd NPs Research Articles

Highly dispersed palladium nanoparticles decorated on nitrogen doped graphene for enhanced photoelectrochemical water splitting

Among various clear energy generation processes, electrocatalytic water splitting or hydrogen evolution reaction (HER) has been considered as an efficient method for the sustainable production of hydrogen (H2) fuel. But, significant efforts are still required to develop cheap, effective and stable electrocatalysts for water splitting to achieve the economical production of H2. In the quest of finding cheap electrocatalysts, herein, we demonstrate the preparation of palladium (Pd) nanoparticles decorated nitrogen (N) doped highly reduced graphene oxide (NDG-Pd) based electrocatalysts. The nitrogen (N) doped highly reduced graphene oxide (NDG) was produced by using graphene oxide as precursor, which was reduced and doped with nitrogen, simultaneously in one-step hydrothermal method. Subsequently, Pd nanoparticles were decorated on the surface of NDG using a facile ultrasonic method to produce NDG-Pd. In order to restrict the amount of precious metal to reduce the cost of catalysts, very small percentage of Pd, such as, 1 and 3 % was utilized during the preparation of electrocatalysts. The as-prepared electrocatalysts were successfully characterized by using different methods such as, XRD, XPS, EDX, BET, SEM and TEM. Results confirmed the formation of slightly agglomerated, smaller size of Pd NPs on the surface of NDG with an average particle size of ∼ 6 nm. The as prepared nanocomposites NDG, NDG-Pd1% and NDG-Pd3% were used to prepare electrodes and their electrocatalytic activity was evaluated towards the production of H2 through water splitting. The results of electrochemical performance of as-prepared electrodes within the voltage range have revealed that among different samples prepared, the NDG did not show any current, whereas NDG-Pd3% showed a good potential for HER with current density ≈24 mA/cm2 at very low potential i.e. −0.2 V vs RHE.

Construction of Pd@K-Silicalite-1 via in situ encapsulation and alkali metal modification for catalytic elimination of formaldehyde at room temperature

The Silicalite-1-encapsulated Pd catalyst with alkali metal K modification (Pd@K-Silicalite-1) was prepared via the hydrothermal method with ethylenediamine as ligand and KOH as precursor of K promoter. The introduction of K partially replaced H of silanol in Silicalite-1 and induced the formation of Si-O-K-Pd species, which were beneficial for the improvement of Pd dispersion. The Pd nanoparticles with a size of ca. 1.9 nm were uniformly encapsulated in the matrix of Silicalite-1 zeolite. The catalytic activity of Pd@K-Silicalite-1 was much better than those of Pd/Silicalite-1 and Pd@Silicalite-1 for HCHO oxidation, HCHO conversion could reach 100 % over Pd@K-Silicalite-1 (Pd content = 0.15 wt%) at room temperature under space velocity (SV) of 120,000 mL/(g × h) and relative humidity (RH) of 35 %. Based on the results of various characterization techniques, one can conclude that the improvement in catalytic activity of Pd@K-Silicalite-1 was attributable to high dispersion and small size of Pd NPs and enhanced HCHO adsorption capacities. In addition, we investigated the reaction mechanism of HCHO oxidation over the Pd@K-Silicalite-1 catalyst by in situ DRIFTS spectra. This work provides some guidance on developing high-performance catalysts for HCHO elimination via in situ encapsulation and alkali metal modification.

In situ study of catalytic CO oxidation on ultrathin MgO film supported Pd nanoparticles by sum frequency generation: size and site effects.

Controlling the reactive sites of nanoparticles (NPs) is crucial to improve catalyst efficiency. In this work, sum-frequency generation is used to probe CO vibrational spectra on MgO(100) ultrathin film/Ag(100) supported Pd nanoparticles ranging from 3 to 6 nm in diameter and compared to those of coalesced Pd NPs and Pd(100) single crystals. We aim to demonstrate in situ the role played by active adsorption sites in the catalytic CO oxidation reactivity trends varying with the NP size. From ultrahigh vacuum to the mbar range and temperatures from 293 K to 340 K, our observations suggest that bridge sites are the main active sites for CO adsorption and catalytic oxidation. On Pd(100) single crystals at 293 K, CO oxidation predominates over CO poisoning at a pressure ratio of O2/CO greater than 300; on Pd NPs, both the site coordination due to NP geometry and MgO-induced Pd-Pd interatomic distance change impact the reactivity trend varying with size in different ways. Edge sites with low coordination are more reactive than facet sites, while facet sites with a smaller Pd-Pd atomic length are more reactive than that with a larger length. The interplay of both site and size effects gives rise to a non-monotonic reactivity trend of CO on the MgO(100) ultrathin film supported Pd NPs: the reactivity of Pd NPs increases for the smaller NP size side due to a higher edge/facet ratio and meanwhile increases for the larger NP size side due to the terrace facet with a smaller Pd-Pd atomic length at the NP surface and a lower diffusion barrier.

In Vitro and Ex Vivo Investigation of the Effects of Polydopamine Nanoparticle Size on Their Antioxidant and Photothermal Properties: Implications for Biomedical Applications

Polydopamine (PDA) is a polymer that derives from the self-polymerization of the biomolecule dopamine. It can be easily synthesized to obtain spherical nanoparticles (PDNPs), tunable in terms of size, loaded cargo, and surface functionalization. PDNPs have been increasingly attracting the attention of the research community due to their elevated versatility in the biomedicine field, for their excellent ability to encapsulate drugs, to convert near-infrared (NIR) radiation into heat, and to act as an antioxidant agent. Size is an important aspect to be considered, especially concerning the specific intended field of application. This work aims at investigating how changes in the size of PDNPs affect the nanoparticle properties relevant for biomedical applications, especially focusing on cancer nanomedicine. A library of differently sized PDNPs (from 145 to 957 nm) has been obtained by varying the ammonia/dopamine molar ratio during the synthesis procedure, and detailed characterization in terms of biocompatibility, cell internalization, antioxidant capacity, and photothermal conversion has been carried out. Experiments showed that nanoparticles with a larger diameter display higher NIR absorbance, superior resistance to degradation, and higher photothermal conversion capacity (the latter confirmed by a mathematical model). On the other hand, a reduction in diameter size induces both improved antioxidant properties and enhanced cellular uptake. Herein, we provide a useful tool, allowing one to choose the proper size of PDNPs tailored for specific biomedical applications.

Suzuki–Miyaura Cross-Coupling Reaction with Potassium Aryltrifluoroborate in Pure Water Using Recyclable Nanoparticle Catalyst

AbstractThis paper describes the Suzuki–Miyaura cross-coupling reaction of aryl bromides with potassium aryltrifluoroborates in water catalyzed by linear polystyrene-stabilized PdO nanoparticles (PS-PdONPs). The reaction of aryl bromides having electron-withdrawing groups or electron-donating groups took place smoothly to give the corresponding coupling product in high yields. The catalyst recycles five times without significant loss of catalytic activity although a little bit increase in size of PdNPs was observed after the reaction.

Palladium nanoparticles decorated on ZSM-5 derived micro-/mesostructures (MMZ) for nitrophenol reduction and MB degradation in water

Palladium-based catalysts are promising for catalytic reduction in catalysis. The dispersion state of palladium nanoparticles (Pd NPs) impacts the catalytic performance, while the development of catalysts with highly dispersed Pd NPs is a major challenge. Herein, we developed ZSM-5 derived micro-/mesoporous silica MMZ to regulate Pd NPs size and dispersion. MMZ was synthesized by combined dissolution of ZSM-5 under basic condition and re-assembly of Al-or Si-containing species of ZSM-5 by cetyltrimethylammonium bromide (CTAB) instead of expensive carbon nanofiber reported earlier. The Pd precursor is introduced into MMZ by ultrasound assisted incipient wetness impregnation (U-IWI) strategy. Up to 1.0 wt% Pd was highly dispersed per g of MMZ without showing any X-ray diffraction lines (denoted as 1.0 Pd/MMZ), while obvious diffraction lines were noticed in the counterpart synthesized from ZSM-5 (denoted as 1.0 Pd/ZSM-5). Further calculation shows the size of Pd NPs in 1.0 Pd/MMZ is 3.5 nm, which is smaller than that in 1.0 Pd/ZSM-5. Our results also demonstrated that well-dispersed and smaller size Pd NPs corresponds to superior catalytic activity in reduction of p-nitrophenol (P-NP) and methylene blue (MB). The typical catalyst 1.0 Pd/MMZ exhibited complete reduction of P-NP and MB in water within 3 min. It is superior to 1.0 Pd/ZSM-5 catalyst with the same Pd content as well as to several reported catalysts. Furthermore, 1.0 Pd/MMZ not only keeps high catalytic activity for 6 consecutive cycles, but also exhibit long-term stability in hydrogenation reaction.

Generation and characterization of palladium nanocatalyst anchored on a novel polyazomethine support: Application in highly efficient and quick catalytic reduction of environmental contaminant nitroarenes

Removal of toxic nitroarenes, which threaten all living organisms and environment, from wastewaters has been an important and prior issue. Therefore, the focus of the present study was to fabricate an effective, fast, reusable, and easily recoverable heterogeneous Pd nanoparticles (Pd NPs) supported on a novel polyazomethine having phenol group (Pd NPs@ P(3-M-4-PAP)) for removal of several hazardous nitroarenes by catalytic reduction from water. Firstly, a novel polyazomethine featuring phenol group was prepared as a stabilizer and then, Pd NPs were anchored on it. Characterizations of the materials were performed by XRD, UV–Vis, FTIR, 1H-NMR, TGA, FE-SEM, EDS and TEM techniques. The obtained TEM analysis results showed that the size of Pd NPs was about 50 nm. Then, catalytic ability of Pd NPs@P(3-M-4-PAP) was investigated in reduction of harmful nitroarenes to useful aniline derivatives in water. Catalytic tests revealed that Pd NPs@P(3-M-4-PAP) had outstanding catalytic efficiency against reduction of different nitroarenes by giving excellent yields (up to 98%), in very short time (between 22s and 70s) with 2 mg nanocatalyst. Moreover, performed reusability test results demonstrated that the Pd NPs@P(3-M-4-PAP) could be recurrently reusable and easily recoverable.

Flexibility Induced Encapsulation of Ultrafine Palladium Nanoparticles into Organic Cages for Tsuji-Trost Allylation.

A series of three positional isomers of organic cages namely o-OC, m-OC, and p-OC, have been self-assembled using dynamic covalent chemistry. Their room temperature controlled fabrication with palladium gives ultrafine diameter (1-2 nm) of palladium nanoparticles (Pd NPs). We observed that the shape-flexibility of cages have great impact on the formation of Pd NPs. Theoretical calculations reveals that theoretically obtainable size of Pd NPs for each cage which was complementary to the experimental results. Theoretical studies indicate that the driving forces for the specific orientational preference may be ascribed to subtle variations on the level of π-π interactions, which ultimately governs the growth of Pd NPs therein. It is the first example of shape-flexible synthesis of organic cages where flexibility governs the nanoparticle growth. Pd NPs have shown excellent catalysis of Tsuji-Trost allylation at room temperature and pressure in water.

Electronic/steric effects in hydrogenation of nitroarenes over the heterogeneous Pd@BEA and Pd@MWW catalysts

Abstract Hydrogenation of nitroarenes is a catalytic reaction of high interest owing to the importance of the resulting aromatic amines in the chemical industry. Up to date, various metal@zeolite catalysts have been reported for this transformation. Herein, Pd@Beta and Pd@MWW catalysts were synthesized by ion exchange with Pd(NH3)4(NO3)2 and characterized by XRD, nitrogen sorption, ICP-OES, electron microscopy and FTIR(CO). Structural and textural analysis proved no significant changes of the zeolites after the Pd precursor was introduced. STEM images proved the uniform distribution of metal species in zeolite crystals. Average size of Pd NPs is 2.6 nm and 1.7 nm for Beta and MWW zeolites, respectively. The resulting Pd@Beta catalyst exhibited higher catalytic activity compared to Pd@MWW in the hydrogenation of nitroarenes. The electronic/steric effects of substrates and products were also investigated for both catalysts. Nitroarenes with electron-donating groups exhibit higher initial reaction rates than nitroarenes containing electron-withdrawing groups. The nitroarenes bearing functionalized groups in the ortho-position are harder to hydrogenate than corresponding meta- and para- isomers because of the steric hindrance effect.

Quaternized polyhedral oligomeric silsesquioxanes stabilized Pd nanoparticles as efficient nanocatalysts for reduction reaction

Hydrophilic quaternized polyhedral oligomeric silsesquioxane (QPOSS) stabilized palladium nanoparticles hybrids (PdNPs@QPOSS) were successfully constructed for catalytic reduction of organic dyes and nitrophenols. The size of PdNPs can be effectively regulated through the molar ratio between QPOSS and Pd precursors. Uniformly dispersed nano-sized QPOSS encapsulated ultra-fine PdNPs with average diameter of 2.38 nm were obtained as the molar ratio of precursors was 1:8. It was found that low-dose PdNPs@QPOSS nanohybrids as catalysts exhibited outstanding catalytic reduction activity for methylene blue (MB) and nitrophenol (4-NP) with high conversion frequencies (TOF) of 213.7 and 17.8 min−1 respectively, which is superior to commercial Pd/C catalyst. The nanocatalysts we prepared could be stably dispersed in water for one month and there was no significant loss of catalytic activity in four catalytic cycle. The enhanced catalytic activity and good stability can be attributed to QPOSS as a stabilizer having strong coordination with as-generated PdNPs. In addition, we evaluated the decolorizing properties of common organic pollutants including methyl orange (MO), congo red (CR), methyl orange (MO), rhodamine 6G (R6G), rhodamine B (RhB), rhodamine 6G (R6G), and nitrophenol derivatives. The organic-inorganic hybrid nanocatalyst PdNPs@QPOSS is very effective in catalytic reduction of a series of colored dyes and nitrophenols, which also means that the nanohybrid as catalyst has a wide range of applications in industrial degradation of organic pollutants in wastewater.

Triazole‐based ligands functionalized silica: Effects of ligand denticity and donors on catalytic oxidation activity of Pd nanoparticles

Triazole‐based ligands, tris (triazolyl)methanol (Htbtm), bis (triazolyl)‐phenylmethanol (Hbtm), and phenyl (pyridin‐2‐yl)(triazolyl)methanol (Hpytm), with differences in ligand denticity (i.e., bidentate and tridentate) and type of N donors (i.e., triazole and pyridine) were functionalized onto a silica support to produce the corresponding SiO2‐L (L = tbtm, btm, pytm). Subsequent reactions with Pd (CH3COO)2 in CH2Cl2 yielded Pd/SiO2‐L. ICP‐MS reveals that Pd loadings are higher with increased N loadings, resulting in the following trend: Pd/SiO2‐tbtm (0.83 mmol Pd g−1) > Pd/SiO2‐btm (0.65 mmol Pd g−1) ~ Pd/SiO2‐pytm (0.63 mmol Pd g−1). Meanwhile, TEM images of the used Pd/SiO2‐L catalysts after the first catalytic cycle show that the mean size of Pd NPs is highest with Pd/SiO2‐pytm (8.5 ± 1.5 nm), followed by Pd/SiO2‐tbtm (6.4 ± 1.6 nm) and Pd/SiO2‐btm (4.8 ± 1.3 nm). Based on TONs, catalytic studies toward aerobic oxidation of benzyl alcohol to benzaldehyde at 60 °C in EtOH showed that Pd/SiO2‐pytm possessed the most active surface Pd(0) atoms, most likely as a result of more labile properties of the pyridine–triazole ligand compared to tris‐ and bis (triazolyl) analogs. ICP‐MS and TEM analysis of Pd/SiO2‐btm indicate minimal Pd leaching and similar average Pd NPs sizes after 1st and 5th catalytic runs, respectively, confirming that SiO2‐btm is an efficient Pd NPs stabilizer. The Pd/SiO2‐btm catalyst was also active toward aerobic oxidation of various benzyl alcohol derivatives in EtOH and could be reused for at least 7 reaction cycles without a significant activity loss.

A highly efficient thermo responsive palladium nanoparticles incorporated guar gum hydrogel for effective catalytic reactions

Hydrogel, especially stimuli responsive hydrogel, has attracted enormous attention due to its unique properties for many applications. Herein, Pd NPs@ CNCs was firstly attained by in situgeneration of Pd NPs onto CNCs, and subsequently incorporated into guar gum-based hydrogel, so that a thermo responsive Pd NPs@ CNCs/ guar gum hydrogel catalytic system was obtained. The sol-gel transition was achieved viaa simple heating/cooling cycle: a sol state was obtained above 70 °C, allowing the catalytic reaction; a gel state was attained below 20 °C, allowing the reuse/ recycling of the Pd NPs. Pd NPs were formed by in situ reduction of PdCl2 in the presence of CNCs so that Pd NPs were loaded onto CNCs surfaces. CNCs acted as stabilizers for the Pd NPs. The TEM image showed that the average size of Pd NPs is ˜3 nm. Subsequently, the Pd NPs@ CNCs composites were loaded into the guar gum hydrogel, based on the boron crosslinking chemistry. The hydrogel exhibited rapid sol-gel transition process upon heating (70 °C) and cooling (20 °C) cycles. The Pd NPs loaded sol-gel transition concept was subsequently applied to the Suzuki coupling reactions between aryl bromides and phenyl boronic acids, and a highly efficient catalytic performance (over 85% yield within 2 h) was obtained. The reuse/recycling of the thermo responsive Pd NPs@ CNCs/guar gum hydrogel catalyst system was investigated. This novel Pd NPs loaded thermo-responsive sol-gel transition concept is a promising new catalytic system.

Green synthesis of Pd truncated octahedrons using of firmiana simplex leaf extract and their catalytic study for electro‐oxidation of methanol and reduction of p‐nitrophenol

A facile and eco‐friendly biosynthetic route for preparing Pd truncated octahedrons (PdTOs) using firmiana simplex leaf extract was reported without any chemical reducing agents. The information of reducing components, reduction process and time were obtained by ATR‐FTIR imaging, FTIR and UV–Vis spectroscopy, respectively. TEM image revealed that more than 75% of PdNPs were composed of PdTOs with an average diameter of 9.2 nm. HR‐TEM analysis demonstrated that a single PdTO consisted of the mix of {100} and {111} crystal planes. SAED and XRD pattern confirmed the well crystalline nature of fcc structured PdTOs. The model reactions of electro‐oxidation of methanol and reduction of p‐nitrophenol (p‐NP) were adopted to explore the effects of structure and size of PdNPs on the catalytic properties. In the electro‐oxidation of methanol, the forward‐scan peak current density (If) of PdTOs was 10.05 mA cm‐2, 6.3 times and 1.9 times of PdNPs‐0 and PdNPs‐4:1, illustrating its superior electro‐catalytic property to that of spherical PdNPs. In the p‐NP reduction reaction, the apparent rate constant (Ka) over PdTOs was 0.358 min‐1, higher than spherical PdNPs‐0 (0.08 min‐1) with the similar particle size and lower than the same spherical PdNPs‐4:1 (0.562 min‐1) and commercial Pd/C (0.415 min‐1), which all about half the size of PdTOs. It has been demonstrated that electro‐chemical oxidation of methanol was a structure‐sensitive reaction, while the reduction of p‐NP was mainly dependent on the particle size of PdNPs.

Sonochemical reduction method for synthesis of TiO2[sbnd]Pd nanocomposites and investigation of anode and cathode catalyst for ethanol oxidation and oxygen reduction reaction in alkaline medium

The development of the superior Pt-free electrocatalyst for enhancing electrocatalytic activity and stability towards the EOR (ethanol oxidation reaction) and ORR (oxygen reduction reaction) are very important for the commercialization of fuel cells. In this work, the palladium nanoparticles (Pd NPs) deposited on titanium dioxide nanospheres (PdTiO2) were successfully prepared by the sonochemical reduction method. Hence, the TiO2 nanospheres were directly used as the templates for nucleation and growth of Pd NPs over their surface using PdCl4− as the Pd precursor, PVP (Polyvinylpyrrolidone) as the stabilizer, ascorbic acid (AA) as the reducing agent, and water as the solvent. The size of Pd NPs is remarkably controlled using the sequential reduction steps by adding an excess of PdCl4−. The excellent electrocatalytic activity towards EOR and ORR is ascribed by the synergistic effect of the Pd nanoparticles and TiO2 nanospheres support. This unique nanocomposite should be of great benefit to the construction of commercial fuel cell systems.

Interfacial Phenomenon and Nanostructural Enhancements in Palladium Loaded Lanthanum Hydroxide Nanorods for Heterogeneous Catalytic Applications

Hydrogenation and cross-coupling reactions are of great importance for industrial applications and noble metal based catalysts are filling the void since the last few decades. However, the high cost of noble metals and poor recycling performance provides an opportunity for chemists to look for alternate options. Herein, we present the use of Lanthanum hydroxide as support for loading ultra-low amount of Pd for hydrogenation and cross-coupling reactions. Lanthanum hydroxide having controlled morphologies comprises exposed crystallographic facets which interact with small sized Pd NPs and shows versatile and effective catalytic performance. The reduction of 4-NP over Pd/La(OH)3 was achieved within very short time (45s) with a rate constant of 60 × 10−3 s−1. The hydrogenation of styrene was also accomplished within 1 hour with much high TOF value (3260 h−1). Moreover, the Suzuki cross-couplings of iodobenzene and phenyl boronic acid into biphenyl completed within 35 min with a TOF value of 389 h−1. The strong interfacial electronic communication regulates electron density of catalytic sites and lowers energy for adsorption of reactant and subsequently conversion into products. Moreover, abundant hydroxyl groups on the surface of La(OH)3, large surface area, mono-dispersity and ultra-small size of Pd NPs also favors the efficient conversion of reactants.

Palladium nanoparticles supported on ceria thin film for capillary microreactor application

Ceria thin film in capillary microreactor was developed as a catalyst support for palladium nanoparticles (Pd NPs) by sol–gel approach. The thickness of Pd/CeO2 film deposited in capillary of 250μm internal diameter is 200nm as measured by scanning electron microscope (SEM), and the particle size of Pd NPs as determined by the transmission electron microscope (TEM) images is 4.2nm. The Pd/CeO2 immobilized capillary was tested for hydrogenation of phenylacetylene in a microreactor at temperature range of 30–60°C. Higher selectivity toward ethylbenzene was recorded at higher temperature. The reaction rate of 1.89×10−3molg−1s−1 was obtained for 158ppm phenylacetylene hydrogenation at 60°C and 0.50mlmin−1 hydrogen flow rate. The ceria thin film was stable even after 6 days.

Gamma radiation mediated green technology for Pd nanoparticles recovery from wastewater

Abstract We describe a facile, economic, and environment friendly green method for simultaneous detection of palladium ions (Pd2+) and recovery Pd nanoparticles (Pd NPs) from wastewater through a non-toxic gamma-irradiation based reduction reaction. Basic orange 2 (BO), an azo dye, is used as a sensing probe in Pd2+ detection and acts as a stabilizing agent in the recovery of monodispersed small Pd NPs. The presence of Pd2+ in waste water was easily observed by naked eye through the color change from yellow to red upon adding the Basic orange 2. More importantly, Pd forms a square-planar structured complex with Pd2+ which aids the development of smaller and monodispersed Pd NPs during radiolytic reduction. The size control mechanism during the recovery of Pd NPs was ascertained by varying the intensity of gamma-ray (from 10 to 50 kGy) and initial concentrations of Pd2+ (from 20 to 100 ppm). We are able to control the size of Pd NPs from 5 to 400 nm by irradiating gamma-ray doses from 1 and 50 kGy, as evident from UV-vis absorption spectra (UV-vis) and transmission electron microscopy (TEM) images. About 15 nm colloidal Pd NPs were formed at 10 kGy gamma-irradiation, and various sizes of aggregates, which may be attributed to Ostwald ripening crystal growth, were observed in the irradiation condition of 20 to 50 kGy. Further, the size of the recovered Pd NPs increases as the Pd2+ concentration increased, due to the increase in the ion association rate. Our proposed green method is a promising strategy that can easily detect Pd2+ from waste water and recover Pd NPs in desired size and morphology.

Size-controllable synthesis and high-performance formic acid oxidation of polycrystalline Pd nanoparticles

A facile approach was developed for the synthesis of polycrystalline palladium nanoparticles (Pd NPs) by using tannic acid (TA) as green reagent and stabilizer in a 30 °C water bath. The size of Pd NPs can be tuned in a range of 10–60 nm simply by adjusting the concentration of Pd precursor. The catalytic activity and stability of the as-obtained Pd NPs toward formic acid oxidation were analyzed. It is found that these Pd NPs with different sizes exhibit size-dependent and enhanced formic acid oxidation performance compared to the commercial Pd black catalyst. It should be noted that the Pd catalysts with an average size of 24 nm demonstrate the best catalytic activity and stability among the other prepared Pd NPs, which can be ascribed to its larger electrochemical surface area (ECSA) and polycrystalline structure with defects.

Sonochemical Reduction Method for Synthesis of TiO2-Pd Nanocomposites and Investigation of Anode and Cathode Catalyst for Ethanol Oxidation and Oxygen Reduction Reaction in Alkaline Medium

This paper describes a sonochemical approach for the synthesis of titanium dioxide nanospheres (TiO2) decorated by palladium nanoparticles (Pd NPs). In this method, the TiO2 nanospheres could be directly used as templates for the nucleation and growth of Pd NPs over their surface using PdCl4 - as the Pd precursor, PVP as the stabilizer, ascorbic acid (AA) as the reducing agent, and water as the solvent. The Pd NPs presented uniform distribution over the TiO2 nanospheres. Remarkably, the size of Pd NPs can be controlled by sequential reduction steps with adding excess of PdCl4 -. The TEM images are well explained that controlled size of Pd NPs as shown in Fig. 1. The electrocatalytic activity of TiO2-Pd electrode materials with size dependent Pd NPs was investigated towards the oxidation of ethanol and reduction of oxygen under alkaline medium. The results indicate that the nanocomposites materials are recognized to be an excellent electrocatalyst due to their excellent corrosion resistance and larger electrochemical active surface area.

Highly sensitive work function hydrogen gas sensor based on PdNPs/SiO2/Si structure at room temperature

In this study, fabrication of highly sensitive PdNPs/SiO2/Si hydrogen gas sensor using experimental and theoretical methods has been investigated. Using chemical method the PdNPs are synthesized and characterized by X-ray diffraction (XRD). The average size of PdNPs is 11nm. The thickness of the oxide film was 20nm and the surface of oxide film analyzed using Atomic-force microscopy (AFM). The C-V curve for the PdNPs/SiO2/Si hydrogen gas sensor in 1% hydrogen concentration and at the room temperature has been reported. The response time and recovery time for 1% hydrogen concentration at room temperature were 1.2s and 10s respectively. The response (R%) for PdNPs/SiO2/Si MOS capacitor hydrogen sensor was 96%. The PdNPs/SiO2/Si MOS capacitor hydrogen sensor showed very fast response and recovery times compared to SWCNTs/PdNPs, graphene/PdNPs, nanorod/PdNPs and nanowire/PdNPs hydrogen gas sensors.