Biosynthesis Parameters Control the Physicochemical and Catalytic Properties of Microbially Supported Pd Nanoparticles

The biosynthesis of Pd nanoparticles supported on microorganisms (bio-Pd) is achieved via the enzymatic reduction of Pd(II) to Pd(0) under ambient conditions using inexpensive buffers and electron donors, like organic acids or hydrogen. Sustainable bio-Pd catalysts are effective for C-C coupling and hydrogenation reactions, but their industrial application is limited by challenges in controlling nanoparticle properties. Here, using the metal-reducing bacterium Geobacter sulfurreducens, it is demonstrated that synthesizing bio-Pd under different Pd loadings and utilizing different electron donors (acetate, formate, hydrogen, no e- donor) influences key properties such as nanoparticle size, Pd(II):Pd(0) ratio, and cellular location. Controlling nanoparticle size and location controls the activity of bio-Pd for the reduction of 4-nitrophenol, whereas high Pd loading on cells synthesizes bio-Pd with high activity, comparable to commercial Pd/C, for Suzuki-Miyaura coupling reactions. Additionally, the study demonstrates the novel synthesis of microbially-supported ≈2 nm PdO nanoparticles due to the hydrolysis of biosorbed Pd(II) in bicarbonate buffer. Bio-PdO nanoparticles show superior activity in 4-nitrophenol reduction compared to commercial Pd/C catalysts. Overall, controlling biosynthesis parameters, such as electron donor, metal loading, and solution chemistry, enables tailoring of bio-Pd physicochemical and catalytic properties.

Development of Magnetizable, Nickel-Ferrite-Decorated Carbon Nanocomposites as Hydrogenation Catalyst for Aniline Synthesis

Catalysts with magnetic properties can be easily recovered from the reaction medium without loss by using a magnetic field, which highly improves their applicability. To design such systems, we have successfully combined the magnetic properties of nickel ferrite nanoparticles with the positive properties of carbon-based catalyst supports. Amine-functionalized NiFe2O4 nanoparticles were deposited on the surfaces of nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) and carbon nanolayers (CNL) by using a coprecipitation process. The magnetizable catalyst supports were decorated by Pd nanoparticles, and their catalytic activity was tested through the hydrogenation of nitrobenzene (NB). By using the prepared catalysts, high nitrobenzene conversion (100% for 120 min at 333 K) and a high aniline yield (99%) were achieved. The Pd/NiFe2O4-CNL catalyst was remarkable in terms of stability during the reuse tests due to the strong interaction formed between the catalytically active metal and its support (the activity was retained during four cycles of 120 min at 333 K). Furthermore, despite the long-lasting mechanical stress, no significant palladium loss (only 0.08 wt%) was detected.

PdCu alloy prepared by ultrasonic method catalyzes the degradation of p-nitrophenol

PdCu alloy nanocatalysts supported on NiFe layered double hydroxide (PdCu-LDHs) were prepared by a green ultrasound-assisted reduction method. The cavitation effect of ultrasound made part of CO₃^2- decompose to CO₂, and NO₃^- and Cl^- replace intercalation, which anchor the PdCu between layers. The action of ultrasound dissociated hydroxyl groups (-OH) on surface of LDHs to H· to reduce Cu²⁺ and Pd²⁺ to Cu⁰ and Pd⁰ and Cu promote the synergy between Pd alloy and LDHs. The electronic effects between Cu and Pd improved the catalytic performance for the reduction reaction of 4-NP and the stability of PdCu-LDHs. The PdCu-LDHs prepared at 400 W, 25 kHz, 1 h, can completely degrade p-nitrophenol (4-NP) within 5 min with n(4-NP)/n(Pd) = 50 and n(4-NP)/n(NaBH₄) = 0.15. The TOF value is 988.20 h^-1, which is 27.7 times that of Pd/C catalyst (commercial).

Biomass Valorization to Chemicals over Cobalt Nanoparticles on SBA-15

A series of heterogeneous catalysts based on cobalt supported on SBA-15 were prepared through wet impregnation and co-impregnation assisted by ethylene glycol (EG) methods. The cobalt oxide catalysts generated after the drying and calcination process were denoted as CoO/SBA-15w and CoO/SBA-15c for a wet- and co-impregnation method, respectively. Subsequent to the reduction process, the reduced cobalt catalysts were obtained and denoted as Co/SBA-15w and Co/SBA-15c. The TEM images revealed the catalysts prepared through these methods show very clear distinctions that the catalyst prepared by wet impregnation shows large aggregates of cobalt particles on the external surface of SBA-15 due to their inability to enter the channels. The catalysts were evaluated on the hydrocracking of pyrolyzed -cellulose as a biomass model. The results showed that the reduced cobalt-based catalysts are having higher conversion value and selectivity towards the 2-furancarboxaldehyde reached ca. 20%. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA   License (https://creativecommons.org/licenses/by-sa/4.0). 

Fluorescent carbon dots from water hyacinth as detection sensors for ferric ions: the preparation and optimisation using response surface methodology

The search for alternatives to chemicals from natural products as precursors for the preparation of highly doped carbon dots (CDs) remains challenging. Novel CDs (W-CDs) were synthesised using a one-step pyrolysis method with wastewater hyacinth as the sole carbon and nitrogen source at a mild temperature without using any surface-activating reagents or salt. The obtained W-CDs emitted strong blue fluorescence under 365 nm UV light excitation, with a quantum yield of 15.12%. The Box-Behnken design of the response surface methodology was applied to optimize the W-CD preparation conditions, including the reaction temperature, reaction time and weight of water hyacinths. The temperature was found to be the most important factor affecting the fluorescence intensity of the W-CDs. Additionally, the fluorescence sensor based on W-CDs demonstrated excellent selectivity towards ferric (Fe) ions, with a limit of detection of 2.35 μM. The fluorescent sensor was successfully applied for detecting Fe³⁺ in real water samples with a recovery of 97.80-103.10%. Hence, the pyrolysis of water hyacinth is proven to be a rapid, effective and green approach for CDs and provides a novel method for recycling water hyacinth.

Nanostructural synergism as MnNC channels in manganese (IV) oxide and fluffy g-C3N4 layered composite with exceptional catalytic capabilities

The avenues of catalysis and material science are always accepted and it is hoped that a state-of-the-art catalyst with exceptional intrinsic redox characteristics would be produced. This study focused on developing a multi-featured catalyst of high economical and commercial standards to meet the multi-directional applications of environmental and energy demands. Manganese (IV) oxide nanosheets made of fluffy-sheet-like g-C₃N₄ material were successfully synthesized by pyrolysis method. The electron-rich g-C₃N₄ network and semiconducting metallic oxides of MnO₂ nanosheets generated high electron density interfaces within the intra-composite structure. The input of active interfaces along with strong metal-to-support interactions achieved between two parallel nanosheets in MnO₂/g-C₃N₄ catalyst intrinsically boosted up its electrochemical and optical characteristics for it to be used in multi-catalytic fields. Successful trails of catalysts' performance have been made in three major catalytic fields with enhanced activities such as heterogeneous catalysis (reduction of nitrobenzene with rate constant of "K = 0.734 min^-1" and hydrogenation of styrene with "100% conversion" efficiency, including negligible change in five consecutive cycles), photocatalysis (degradation of methylene blue dye model within 20 min with negligible change in five consecutive cycles) and electrocatalysis (oxygen reduction reactions having comparable "diffusion-limited-current density" behaviour with that of the commercial Pt/C catalyst). The enhanced performance of catalysts in transforming chemicals, degrading organic pollutant species and producing sustainable energy resources from air oxygen can mitigate the challenges faced in environmental and energy crises, respectively.

Preparation of highly effective carbon black supported Pd-Pt bimetallic catalysts for nitrobenzene hydrogenation

Carbon black (CB) supported palladium-platinum catalysts were prepared with and without nickel(II) oxide or iron(III) oxide promoter materials. By applying ultrasonic cavitation highly efficient CB supported catalysts were created. The designed catalyst preparation is a one-step procedure, as post-treatments (e.g. calcination, hydrogen activation) are not necessary. The activation of the catalysts occurs during their preparation due to the ultrasonic cavitation. Thus, a fast and simple catalyst preparation procedure have been developed. The activity of the catalysts was compared in nitrobenzene hydrogenation at different temperatures in the range of 283-323 K at 20 bar hydrogen pressure. In terms of selectivity and aniline yield, no significant differences were detected even when promoters were present. By using the NiO promoter, the activation energy was extremely low (7.6 ± 0.7 kJ mol^-1). The selectivity was over 99% in every case, and 99.6% aniline yield was achieved without any promoters (99.7% with NiO), while less than 1.0% by-products were formed. The reaction rate was high with every catalyst, and no significant differences were detected. All in all, the prepared catalysts show excellent catalytic activity in the hydrogenation of nitrobenzene.

Precious-Metal-Decorated Chromium(IV) Oxide Nanowires as Efficient Catalysts for 2,4-Toluenediamine Synthesis

The catalytic hydrogenation of 2,4-dinitrotoluene (DNT) to 2,4-toluenediamine (TDA) is a key step in the production of polyurethanes; therefore, the development of efficient hydrogenation catalysts for industrial use is of paramount importance. In the present study, chromium(IV) oxide nanowires were decorated by palladium and platinum nanoparticles in a one-step, simple, and fast preparation method to yield highly efficient hydrogenation catalysts for immediate use. The nanoparticles were deposited onto the surface of CrO2 nanowires by using ultrasonic cavitation and ethanol as a reduction agent. Beneficially, the catalyst became catalytically active right at the end of the preparation and no further treatment was necessary. The activity of the Pd- and Pt-decorated CrO2 catalysts were compared in the hydrogenation of 2,4-dinitrotoluene (DNT). Both catalysts have shown high activity in the hydrogenation tests. The DNT conversion exceeded 98% in both cases, whereas the 2,4-toluenediamine (TDA) yields were 99.7 n/n% and 98.8 n/n%, with the Pd/CrO2 and Pt/CrO2, respectively, at 333 K and 20 bar H2 pressure. In the case of the Pt/CrO2 catalyst, 304.08 mol of TDA formed with 1 mol Pt after 1 h hydrogenation. Activation energies were also calculated to be approximately 24 kJ∙mol-1. Besides their immediate applicability, our catalysts were well dispersible in the reaction medium (methanolic solution of DNT). Moreover, because of their magnetic behavior, the catalysts were easy to handle and remove from the reaction media by using a magnetic field.

Rigid anchoring of highly crystallized and uniformly dispersed Pd nanocrystals on carbon fibers for ambient electrocatalytic reduction of nitrogen to ammonia

Developing efficient and stable electrocatalysts for ammonia synthesis via the nitrogen reduction reaction (NRR) is essential for the Earth's nitrogen cycle. Herein, a palladium nanocrystals anchored carbon fibers (PdNCs@CNFs) composite was prepared via electrospinning and carbonization processes. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization studies show that the as-prepared Pd grains are homogeneously anchored on the outer/inner section of the carbon nanofibers. Benefiting from the sufficient exposure and stress effect of active sites, the resultant PdNCs@CNFs achieves a high Faraday efficiency of ∼14.8% with a current density of 0.028 mA cm-2 at -0.2 V vs. reversible hydrogen electrode (RHE) in 0.1 M Na2SO4 solution, surpassing those of many catalysts previously reported. Density functional theory (DFT) calculations reveal that the rationality of the distal associative mechanism on PdNCs@CNFs and Pd nanocrystals on the surface of PdNCs@CNFs is more favorable for nitrogen (N2) molecule adsorption and polarization.

Development of Highly Efficient, Glassy Carbon Foam Supported, Palladium Catalysts for Hydrogenation of Nitrobenzene

Glassy carbon foam (GCF) catalyst supports were synthesized from waste polyurethane elastomers by impregnating them in sucrose solution followed by pyrolysis and activation (AC) using N₂ and CO₂ gas. The palladium nanoparticles were formed from Pd(NO₃)₂. The formed palladium nanoparticles are highly dispersive because the mean diameters are 8.0 ± 4.3 (Pd/GCF), 7.6 ± 4.2 (Pd/GCF-AC1) and 4.4 ± 1.6 nm (Pd/GCF-AC2). Oxidative post-treatment by CO₂ of the supports resulted in the formation of hydroxyl groups on the GCF surfaces, leading to a decrease in zeta potential. The decreased zeta potential increased the wettability of the GCF supports. This, and the interactions between -OH groups and Pd ions, decreased the particle size of palladium. The catalysts were tested in the hydrogenation of nitrobenzene. The non-treated, glassy-carbon-supported catalyst (Pd/GCF) resulted in a 99.2% aniline yield at 293 K and 50 bar hydrogen pressure, but the reaction was slightly slower than other catalysts. The catalysts on the post-treated (activated) supports showed higher catalytic activity and the rate of hydrogenation was higher. The maximum attained aniline selectivities were 99.0% (Pd/GCF-AC1) at 293 K and 98.0% (Pd/GCF-AC2) at 323 K.

Catalytic Hydrogenation/Hydrogenolysis of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran

Recent developments in transformations of biobased 5-hydroxymethylfurfural to 2,5-dimethylfuran, a potential liquid fuel, are critically summarized. The highest yield of 2,5-dimethylfuran (more than 98 %) from 5-hydroxymethylfurfural are obtained over bimetallic Cu-Co supported on carbon at 180 °C under 5 bar hydrogen in 2-propanol and over Ni supported on mesoporous carbon at 200 °C under 30 bar hydrogen in water in a batch reactor. The desired catalyst should have relatively high metal dispersion and some acidity to facilitate both hydrogenation and hydrogenolysis. However, overhydrogenation and overhydrogenolysis forming 2,5-dimethyltetrahydrofuran and methylfuran, respectively, should be suppressed. Furthermore, a hydrophobic support is more selective than oxide-based support. After a careful adjustment of the residence time in a continuous reactor it is also possible to produce high yields of 2,5-dimethylfuran even over Pt/C. The main challenges limiting the industrial feasibility of these reactions are relatively low initial reactant concentration, catalyst deactivation by sintering, leaching and coking. In addition to selection of optimum reaction conditions and catalyst properties, kinetic modelling was also summarized.

Realizing Catalytic Acetophenone Hydrodeoxygenation with Palladium-Equipped Porous Organic Polymers

Porous organic polymers (POPs) constructed through covalent bonds have raised tremendous research interest because of their suitability to develop robust catalysts and their successful production with improved efficiency. In this work, we have designed and explored the properties and catalytic activity of a template-free-constructed, hydroxy (-OH) group-enriched porous organic polymer (Ph-POP) bearing functional Pd nanoparticles (Pd-NPs) by one-pot condensation of phloroglucinol (1,3,5-trihydroxybenzene) and terephthalaldehyde followed by solid-phase reduction with H₂. The encapsulated Pd-NPs rested within well-defined POP nanocages and remained undisturbed from aggregation and leaching. This polymer hybrid nanocage Pd@Ph-POP is found to enable efficient liquid-phase hydrodeoxygenation (HDO) of acetophenone (AP) with high selectivity (99%) of ethylbenzene (EB) and better activity than its Pd@Al₂O₃ counterpart. Our investigation demonstrates a facile, scalable, catalyst-template-free methodology for developing novel porous organic polymer catalysts and next-generation efficient greener chemical processes from platform molecules to produce value-added chemicals. With the aid of comprehensive in situ ATR-IR spectroscopy experiments, it is suggested that EB can be more easily desorbed in a solution, reflecting from the much weaker but better-resolved signal at 1494 cm^-1 in Pd@Ph-POP compared to that in Pd@Al₂O₃, which is the key determining factor in favoring an efficient catalytic mechanism. Density functional theory (DFT) calculations were performed to illustrate the detailed reaction network and explain the high catalytic activity observed for the fabricated Pd@Ph-POP catalyst in the HDO conversion of AP to EB. All of the hydrogenation routes, including direct hydrogenation by surface hydrogen, hydrogen transfer, and the keto-enol pathway, are evaluated, providing insights into the experimental observations. The presence of phenolic hydroxyl groups in the Ph-POP frame structure facilitates the hydrogen-shuttling mechanism for dehydration from the intermediate phenylethanol, which was identified as a crucial step for the formation of the final product ethylbenzene. Besides, weaker binding of the desired product ethylbenzene and lower coverage of surface hydrogen atoms on Pd@Ph-POP both contributed to inhibiting the overhydrogenation reaction and explained well the high yield of EB produced during the HDO conversion of AP on Pd@Ph-POP in this study.

NiPd Supported on Mesostructured Silica Nanoparticle as Efficient Anode Electrocatalyst for Methanol Electrooxidation in Alkaline Media

The direct methanol fuel cell (DMFC) is a portable device and has the potential to produce 10 times higher energy density than lithium-ion rechargeable batteries. It is essential to build efficient methanol electrooxidation reaction electrocatalysts for DMFCs to achieve their practical application in future energy storage and conversion. A catalyst consisting of nickel–palladium supported onto mesostructured silica nanoparticles (NiPd–MSN) was synthesized by the wet impregnation method, while MSN was synthesized using the sol-gel method. MSN act as a catalyst support and has very good characteristics for practical support due to its large surface area (>1000 m2/g) and good chemical and mechanical stability. The microstructure and catalytic activity of the electrocatalysts were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), Brunauer–Emmet–Teller (BET) theory, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and chronoamperometry (CA). XRD showed that the NiPd–MSN electrocatalysts had a high crystallinity of PdO and NiO, while FESEM displayed that NiPd was dispersed homogeneously onto the high surface area of MSN. In alkaline media, the catalytic activity toward the methanol oxidation reaction (MOR) of NiPd–MSN demonstrated the highest, which was 657.03 mA mg−1 more than the other electrocatalysts. After 3600 s of CA analysis at −0.2 V (vs. Ag/AgCl), the MOR mass activity of NiPd–MSN in alkaline media was retained at a higher mass activity of 190.8 mA mg−1 while the other electrocatalyst was significantly lower than that. This electrocatalyst is a promising anode material toward MOR in alkaline media.

Optimization of sol-immobilized bimetallic Au-Pd/TiO2 catalysts: reduction of 4-nitrophenol to 4-aminophenol for wastewater remediation

A sol-immobilization method is used to synthesize a series of highly active and stable Au_xPd_1-x/TiO₂ catalysts (where x = 0, 0.13, 0.25, 0.5, 0.75, 0.87 and 1) for wastewater remediation. The catalytic performance of the materials was evaluated for the catalytic reduction of 4-nitrophenol, a model wastewater contaminant, using NaBH₄ as the reducing agent under mild reaction conditions. Reaction parameters such as substrate/metal and substrate/reducing agent molar ratios, reaction temperature and stirring rate were investigated. Structure-activity correlations were studied using a number of complementary techniques including X-ray powder diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. The sol-immobilization route provides very small Au-Pd alloyed nanoparticles, with the highest catalytic performance shown by the Au_0.5Pd_0.5/TiO₂ catalyst. This article is part of a discussion meeting issue 'Science to enable the circular economy'.

Janus coordination polymer derived PdO/ZnO nanoribbons for efficient 4-nitrophenol reduction

Bimetallic coordination polymers–Zn(MAA)₂/Pd(ii) nanoribbons are prepared by employing two terminal units with distinct hard–soft properties of the smallest semi-rigid methacrylate anion to combine with two different metal ions.

The green synthesis of PdO/Pd anchored on hierarchical ZnO microflowers with a synthetic effect for the efficient catalytic reduction of 4-nitrophenol

PdO/Pd anchored on hierarchical ZnO microflowers has excellent development potential for treating dye wastewater.

Sonochemical Deposition of Palladium Nanoparticles Onto the Surface of N-Doped Carbon Nanotubes: A Simplified One-Step Catalyst Production Method

Abstract

This work presents an easy, one-step procedure for catalyst preparation. A small fraction of palladium ions was reduced to Pd nanoparticles and deposited onto the surface of nitrogen-doped carbon nanotubes (N-BCNT) by acoustic cavitation using high-intensity ultrasound in aqueous phase, where N-BCNT served as a reducing agent. The formation of elemental palladium and palladium oxides were confirmed and the particle size is < 5 nm. The catalytic activity of the synthesized Pd/N-BCNT catalyst was tested in nitrobenzene hydrogenation at four different temperature (273–323 K) and 20 bar pressure. The catalyst showed high activity despite the presence of palladium oxide forms, the conversion of nitrobenzene to aniline was 98% at 323 K temperature after 40 min. The activation energy was 35.81 kJ/mol. At 303 K and 323 K temperature, N-methylaniline was formed as by-product in a small quantity (8 mmol/dm3). By decreasing the reaction temperature (at 273 K and 283 K), the reaction rate was also lower, but it was favourable for aniline selectivity, and not formed n-methylaniline. All in all, Pd/N-BCNT catalyst was successfully produced by using a one-step sonochemical method, where further activation was not necessary as the catalytic system was applicable in nitrobenzene hydrogenation.

Graphic Abstract

Electron Beam Induced Enhancement of the Catalytic Properties of Ion-Track Membranes Supported Copper Nanotubes in the Reaction of the P-Nitrophenol Reduction

This study considers the effect of various doses of electron irradiation on the crystal structure and properties of composite catalysts based on polyethylene terephthalate track-etched membranes and copper nanotubes. Copper nanotubes were obtained by electroless template synthesis and irradiated with electrons with 3.8 MeV energy in the dose range of 100–250 kGy in increments of 50 kGy. The original and irradiated samples of composites were investigated by X-ray diffraction technique (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The improved catalytic activity of composite membranes with copper nanotubes was demonstrated by the example of the reduction reaction of p-nitrophenol in the presence of sodium borohydride. Irradiation with electrons at doses of 100 and 150 kGy led to reaction rate constant increases by 35 and 59%, respectively, compared to the non-irradiated sample. This enhancing catalytic activity could be attributed to the changing of the crystallite size of copper, as well as the surface roughness of the composite membrane.

Ruthenium Supported on Ionically Cross-linked Chitosan-Carrageenan Hybrid MnFe2O4 Catalysts for 4-Nitrophenol Reduction

Herein, we report a facile procedure to synthesize the hybrid magnetic catalyst (Ru@CS-CR@Mn) using ruthenium (Ru) supported on ionically cross-linked chitosan-carrageenan (CS-CR) and manganese ferrite (MnFe2O4) nanoparticles with excellent catalytic activity. The ionic gelation of CS-CR is acting as a protecting layer to promote the encapsulation of MnFe2O4 and Ru nanoparticles by electrostatic interactions. The presence of an active metal and a CS-CR layer on the as-prepared Ru@CS-CR@Mn catalyst was well determined by a series of physicochemical analyses. Subsequently, the catalytic performances of the Ru@CS-CR@Mn catalysts were further examined in the 4-nitrophenol (4-NP) reduction reaction in the presence of sodium borohydride (reducing agent) at ambient temperature. The Ru@CS-CR@Mn catalyst performed excellent catalytic activity in the 4-NP reduction, with a turnover frequency (TOF) values of 925 h−1 and rate constant (k) of 0.078 s−1. It is worth to mentioning that the Ru@CS-CR@Mn catalyst can be recycled and reused up to at least ten consecutive cycles in the 4-NP reduction with consistency in catalytic performance. The Ru@CS-CR@Mn catalyst is particularly attractive as a catalyst due to its superior catalytic activity and superparamagnetic properties for easy separation. We foresee this catalyst having high potential to be extended in a wide range of chemistry applications.

Palladium nanoparticle functionalized graphene xerogel for catalytic dye reduction

We report a method to synthesize a palladium-functionalized porous graphene xerogel structure. A graphene xerogel nanocomposite with a three-dimensional microstructure was obtained by chemical reduction of an aqueous dispersion of graphene oxide at mild temperature. After the graphene hydrogel has been placed in a K2PdCl4 solution, the spontaneous redox reaction between the reduced graphene and Pd2+ takes place, leading to the formation of nanohybrid materials consisting of a graphene porous matrix decorated with Pd nanoparticles. The final porosity of the material was tuned through drying the graphene hydrogel by solvent evaporation. The palladium functionalized porous graphene xerogels were successfully used for the catalytic reduction of Rhodamine 6G.

Greener Biogenic Approach for the Synthesis of Palladium Nanoparticles Using Papaya Peel: An Eco-Friendly Catalyst for C-C Coupling Reaction

The development of a green and sustainable synthetic methodology still remains a challenge across the globe. Encouraging the prevailing challenge, herein, we have synthesized Pd nanoparticles (Pd NPs) in a green and environmentally viable route, using the extract of waste papaya peel without the assistance of any reducing agents, high-temperature calcination, and reduction procedures. The biomolecules present in the waste papaya peel extract reduced Pd(II) to nanosize Pd(0) in a one-pot green and sustainable process. As a catalyst, the new Pd NPs offer a simple and efficient methodology in direct Suzuki-Miyaura and Sonogashira coupling with excellent yields under mild reaction conditions.

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.

Supported metal nanoparticles with tailored catalytic properties through sol-immobilisation: applications for the hydrogenation of nitrophenols

Nanoparticle property control, and excellent catalytic capabilities, has been demonstrated using Pd/TiO₂ prepared by sol-immobilisation with solvent and temperature control.

An in situ XAS study of the activation of precursor-dependent Pd nanoparticles

The activation of precursor-dependent Pd nanoparticles was comprehensively followed by in situ X-ray absorption spectroscopy on two inorganic supports for rationalizing the final catalytic activity.

Preparation of supported AuPd nanoalloys mediated by ionic liquid-like functionalized SBA-15: structural correlations concerning its catalytic activity

We report highly active catalysts based on mono- or bimetallic Au and Pd nanoparticles supported in ionic liquid-like modified SBA-15.

Controllable synthesis of a Pd/PdO nanocomposite as a catalyst for hydrogenation of nitroarenes to anilines in water

The different Pd/PdO ratios nanoparticles supported on oxide carbon nanotubes can be controllable synthesized by a one-pot gas–liquid interfacial plasma method, which can catalyze the hydrogenation of nitroarenes in water by atmosphere pressure H₂.

Graphene oxide/carbon nanotubes–Fe3O4 supported Pd nanoparticles for hydrogenation of nitroarenes and C–H activation

The GO/CNT–Fe₃O₄ support Pd nanoparticles are synthesized by the gas–liquid interfacial plasma method. The catalysts exhibit remarkable catalytic activity during the hydrogenation of nitroarenes and C–H functionalization.

Self-assembly of cuprous oxide nanoparticles supported on reduced graphene oxide and their enhanced performance for catalytic reduction of nitrophenols

Mechanism for the catalytic reduction of nitrophenols; the catalyst can be reused with nearly invariable high catalytic efficiency.

A new facile strategy for higher loading of silver nanoparticles onto silica for efficient catalytic reduction of 4-nitrophenol

The facile route to higher loading of silver nanoparticles onto a silica support is useful for large-scale synthesis of efficient silver supported catalysts.