Pd Nanoparticles Research Articles

Nanotransistor-based gas sensing with record-high sensitivity enabled by electron trapping effect in nanoparticles

Highly sensitive, low-power, and chip-scale H2 gas sensors are of great interest to both academia and industry. Field-effect transistors (FETs) functionalized with Pd nanoparticles (PdNPs) have recently emerged as promising candidates for such H2 sensors. However, their sensitivity is limited by weak capacitive coupling between PdNPs and the FET channel. Herein we report a nanoscale FET gas sensor, where electrons can tunnel between the channel and PdNPs and thus equilibrate them. Gas reaction with PdNPs perturbs the equilibrium, and therefore triggers electron transfer between the channel and PdNPs via trapping or de-trapping with the PdNPs to form a new balance. This direct communication between the gas reaction and the channel enables the most efficient signal transduction. Record-high responses to 1–1000 ppm H2 at room temperature with detection limit in the low ppb regime and ultra-low power consumption of ~\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document}300 nW are demonstrated. The same mechanism could potentially be used for ultrasensitive detection of other gases. Our results present a supersensitive FET gas sensor based on electron trapping effect in nanoparticles.

Enhanced DeNOx catalysis: Induction-heating-catalysis-ready 3D stable Ni supported metal combinations

Catalysis plays a critical role in the quest for sustainable automotive technology, particularly in reducing harmful emissions from vehicles. The catalysts are required to operate efficiently in dynamic and challenging environments. This study introduces innovative deNOx catalysts featuring nominal concentrations of Pd and Re nanoparticles doped on a NiMo support. The best-performing fabricated catalyst demonstrated impressive 95 % NOx conversion at 250°C, significantly outperforming traditional systems and reducing ammonia slip. Integrating nickel as the support material was strategic choice to leverage novel induction heating-assisted catalytic system. This approach is particularly advantageous when starting cold engine, reducing harmful NOx emissions when the catalyst is not fully operational. Functional monolith model of car converter catalyst with similar composition was also developed. This research presents novel catalyst solution that achieves high deNOx efficiency while offering a cost-effective alternative to traditional methods. Induction heating enhances the catalyst's performance, particularly at lower temperatures, showcasing significant improvement over conventional thermal methods.

Hydrogen evolution via photocatalytic reforming of biomass with palladium nanoparticles decorated g-C3N4 nanosheets

Fossil fuel depletion and environmental toxins have made photocatalytic H2 production of paramount significance. A novel and unique technique for producing sustainable H2 and valorizing biomass using infinite solar energy is biomass photoreformation. Nevertheless, this environmentally friendly method is usually linked to severe reaction circumstances, insufficient selectivity, and restricted biomass conversion. Here, we present a novel one-pot photoreformation technique over porous g-C3N4 nanosheets surface-modified with Pd nanoparticles to convert d-glucose to H2. By stacking the g-C3N4 photocatalyst into a 2D nanosheet structure, some of its inherent drawbacks can be mitigated. Furthermore, the inclusion of noble metal nanoparticles in these g-C3N4 nanosheet structures could significantly boost existing photocatalytic activity. The majority of solar radiation is composed of visible light, which makes up 45% of it, and ultraviolet light, which makes up 5%. Therefore, our focus has been on utilizing abundant visible light to facilitate biomass reformation. After 4 h of continuous irradiation, our composite photocatalyst exhibited exceptional visible light activity; its H2 evolution was 1839.84 μmolg−1h−1, or about 27 times higher than that of undoped g-C3N4 nanosheets. The effectiveness of three different Pd loadings on g-C3N4 nanosheets for glucose reforming was examined. In the quest for an improved H2 evolution visible light active photocatalyst, g-C3N4 nanosheets made at various pyrolysis temperatures loaded with optimized Pd weight percentage were also examined.

Sub-millisecond pulsed laser engineering of CuOx-decorated Pd nanoparticles for enhanced catalytic CO2 hydrogenation

Catalytic CO2 hydrogenation to fuels and chemicals presents a promising avenue for addressing global warming and advancing toward a net-zero economy. Surface atomic rearrangement of catalysts has attracted growing interest as a means to manipulate catalyst activity and selectivity. Herein, we designed a ternary nanocatalyst comprising CuOx species decorated Pd nanoparticles (NPs) supported on Co oxide (denoted as CPCu) for catalytic CO2 hydrogenation. Sub-millisecond laser treatment (1 mJ per pulse) was used to manipulate the surface atomic arrangements of CPCu the catalyst. The CPCu nanocatalyst showed a significant enhancement in both CH4 production and CO production at 300 °C compared to the Pd/Co catalyst. Notably, the CH4 production using the laser-treated nanocatalyst (denoted as CPCu-L) was 66.6 % higher than the untreated one (CPCu) at 300 °C. Comprehensive catalyst characterizations revealed that CuOx species promoted CO2 activation, while neighboring Pd domains effectively dissociated H2 molecules, leading to enhanced CH4 production. This study demonstrates the potential of sub-millisecond laser treatment for tailoring catalyst surfaces, offering a promising strategy to design more active and selective catalysts for CO2 hydrogenation.

Phosphorus-Modified Palladium and Tungsten Carbide/Mesoporous Carbon Composite for Hydrogen Oxidation Reaction of Proton Exchange Membrane Fuel Cells.

A composite material of tungsten carbide and mesoporous carbon was synthesized by the sol-gel polycondensation of resorcinol and formaldehyde, using cetyltrimethylammonium bromide as a surfactant and Ludox HS-40 as a porogen, and served as a support for Pd-based electrodes. Phosphorus-modified Pd particles were deposited onto the support using an NH3-mediated polyol reduction method facilitated by sodium hypophosphite. Remarkably small Pd nanoparticles with a diameter of ca. 4 nm were formed by the phosphorus modification. Owing to the high dispersion of Pd and its strong interaction with tungsten carbide, the Pd nanoparticles embedded in the tungsten carbide/mesoporous carbon composite exhibited a hydrogen oxidation activity approximately twice as high as that of the commercial Pt/C catalyst under the anode reaction conditions of proton exchange membrane fuel cells.

V-Promoted Ultrasmall Pd Nanoparticles Supported on V-KIT-6 for the Enhanced Catalytic Dehydrogenation of Perhydro-N-ethylcarbazole

V-Promoted Ultrasmall Pd Nanoparticles Supported on V-KIT-6 for the Enhanced Catalytic Dehydrogenation of Perhydro-<i>N</i>-ethylcarbazole

Maximized nanojunctions in Pd/SnO2 nanoparticles for ultrasensitive and rapid H2 detection

H2 energy has gained massive attraction as a promising candidate for future energy sources. However, the explosive properties of H2 arouse significant safety concerns, emphasizing the need for the development of real-time H2 detection systems. This study presents the fabrication of an ultrasensitive and selective H2 gas sensor using Pd/SnO2 nanoparticles (NPs) synthesized through the utilization of Pluronic F-127. Pluronic F-127 improves the dispersion and regulates the particle size of Pd NPs. Pd/SnO2 NPs, which are comprised of numerous nanojunctions, exhibit H2 response of 27,190 and a response time of 3 s when exposed to 50 ppm of H2 at 100 °C. The practical applicability of Pd/SnO2 NPs was demonstrated by detecting H2 generated from water-splitting cells, exhibiting promising features for H2 energy industries. Overall, the synthetic method of this study proposes advanced strategies for development of sensing materials with maximized gas sensing performance.

Phosphorus-Doping Enables the Superior Durability of a Palladium Electrocatalyst towards Alkaline Oxygen Reduction Reactions.

The sluggish kinetics of oxygen reduction reactions (ORRs) require considerable Pd in the cathode, hindering the widespread of alkaline fuel cells (AFCs). By alloying Pd with transition metals, the oxygen reduction reaction's catalytic properties can be substantially enhanced. Nevertheless, the utilization of Pd-transition metal alloys in fuel cells is significantly constrained by their inadequate long-term durability due to the propensity of transition metals to leach. In this study, a nonmetallic doping strategy was devised and implemented to produce a Pd catalyst doped with P that exhibited exceptional durability towards ORRs. Pd3P0.95 with an average size of 6.41 nm was synthesized by the heat-treatment phosphorization of Pd nanoparticles followed by acid etching. After P-doping, the size of the Pd nanoparticles increased from 5.37 nm to 6.41 nm, and the initial mass activity (MA) of Pd3P0.95/NC reached 0.175 A mgPd-1 at 0.9 V, slightly lower than that of Pd/C. However, after 40,000 cycles of accelerated durability testing, instead of decreasing, the MA of Pd3P0.95/NC increased by 6.3% while the MA loss of Pd/C was 38.3%. The durability was primarily ascribed to the electronic structure effect and the aggregation resistance of the Pd nanoparticles. This research also establishes a foundation for the development of Pd-based ORR catalysts and offers a direction for the future advancement of catalysts designed for practical applications in AFCs.

Silica nanospheres-encapsulated polymer ligands-bound Pd nanoparticles as highly efficient and selective catalysts for semi-hydrogenations of alkynes

In this work, we report that poly (acrylic acid) (PAA) and poly (ethylenimine) (PEI) capped Pd nanoparticles (NPs) encaged in hollow silica nanospheres (PAA/PEI-Pd@HSNs) function as highly efficient and selective catalysts for hydrogenations of a series of alkynes. We used the coordination of Pd4+ ions with PEI and PAA to build the micelles system in an ethanol-water system, which was employed as the templates for silica deposition and following NaBH4 reduction to give PAA/PEI-Pd@HSNs. The materials feature polymer-coordinated small Pd NPs inside silica nanospheres with thin shells and large cavities. The PAA/PEI-Pd@HSNs exhibit extremely high catalytic efficiency and reusability with enhanced alkene selectivity of ∼90 % at near complete conversions for hydrogenation of a series of alkynes, and maintain high selectivity even with a significantly extended reaction time. The enhanced catalytic performance of PAA/PEI-Pd@HSNs is ascribed to their thin silica shells/large cavities to improve the catalytic activity, PEI/PAA ligands that inhibit the deep hydrogenation of alkenes to alkanes on Pd NPs, and the protection of silica shells for inner ligands and Pd NPs to improve the reusability.

Facile Abatement of Oxygenated Volatile Organic Compounds via Hydrogen Co-Combustion over Pd/Al2O3 Catalyst as Onsite Heating Source

Catalytic combustion of volatile organic compounds (VOCs) usually requires external energy input to hold the desired reaction temperature via electric heating. This work presents an example of internal onsite heating of the catalytic active sites via hydrogen catalytic combustion with air over a conventional Pd/Al2O3 catalyst. Hydrogen combustion was ignited by the catalyst at room temperature without electric heating, and thus the temperatures were readily varied with the concentrations of H2. Representative oxygenated VOCs such as methanol, formaldehyde and formic acid can be completely oxidized into CO2 and water by co-feeding with H2 below its low explosion limit of 4% using Pd/Al2O3 as shared catalyst. The catalytic performance apparently is not sensitive to the sizes of Pd nanoparticles in fresh and spent states, as revealed by XRD and STEM. This provides an option for using renewable green hydrogen to eliminate VOC pollutants in an energy-efficient way.

Solid‐state Suzuki–Miyaura cross‐coupling: A sustainable approach by DDIL‐stabilized magnetic separable and recyclable Pd nanoparticles with total solvent bypass

A new method for the sustainable synthesis of various functionalized biaryls through the solid‐state Suzuki–Miyaura cross‐coupling reaction has been developed. This solid‐state protocol employs a palladium catalyst anchored on diazabicyclo[2.2.2]octane silica ferrite composite (Pd‐DDIL@Fe3O4‐SiO2). The catalyst has been fully characterized using multiple techniques such as FTIR, XRD, FESEM, EDS, elemental mapping, HR‐TEM, XPS, BET, TGA‐DTA, and VSM. The Pd‐DDIL@Fe3O4‐SiO2 catalyst has a surface area of 60.17 m2 g−1 and a magnetization saturation of 40.95 emu g−1. The TEM analysis revealed the rough spherical morphology of PdNPs having a particle size of 7 nm. The catalyst has excellent activity and selectivity towards the synthesis of both symmetrical and unsymmetrical biaryls under solid‐state, solvent‐free grinding conditions using a mortar and pestle. This method is eco‐friendly, as it is performed at room temperature without any solvents. The method employs the excellent yield of the products (90–96%) in a short reaction time (3–20 min). The desired products are isolated easily without any use of organic solvents. The catalyst can be easily separated using an external magnet and reused at least six times with an admirable change in yield. Additionally, the catalytic system has been shown to have a high TON and TOF, thus confirming its sustainability.

One-Pot Synthesis of Pd Nanoparticles Supported on Carbide-Derived Carbon for Oxygen Reduction Reaction.

We explored two methods for synthesizing Pd nanoparticles using three different carbide-derived carbon (CDC) support materials, one of which was nitrogen-doped. These materials were studied for oxygen reduction reaction (ORR) in 0.1 M KOH solution, and the resulting CDC/Pd catalysts were characterized using TEM, XRD, and XPS. The citrate method and the polyol method using polyvinylpyrrolidone (PVP) as a capping agent were employed to elucidate the impact of the support material on the final catalyst. The N-doping of the CDC material resulted in smaller Pd nanoparticles, but only in the case of the citrate method. This suggests that the influence of support is weaker when using the polyol method. The citrate method with CDC1, which is predominantly microporous, led to a higher degree of agglomeration and formation of larger particles in comparison to supports, which possessed a higher degree of mesoporosity. We achieved smaller Pd particle sizes using citrate and NaBH4 compared to the ethylene glycol PVP method. Pd deposited on CDC2 and CDC3 supports showed similar specific activity (SA), suggesting that the N-doping did not significantly influence the ORR process. The highest SA value was observed for CDC1/Pd_Cit, which could be attributed to the formation of larger Pd particles and agglomerates.

Steering Photooxidation of Methane to Formic Acid over A Priori Screened Supported Catalysts.

Efficient methane photooxidation to formic acid (HCOOH) has emerged as a sustainable approach to simultaneously generate value-added chemicals and harness renewable energy. However, the persistent challenge lies in achieving a high yield and selectivity for HCOOH formation, primarily due to the complexities associated with modulating intermediate conversion and desorption after methane activation. In this study, we employ first-principles calculations as a comprehensive guiding tool and discover that by precisely controlling the O2 activation process on noble metal cocatalysts and the adsorption strength of carbon-containing intermediates on metal oxide supports, one can finely tune the selectivity of methane photooxidation products. Specifically, a bifunctional catalyst comprising Pd nanoparticles and monoclinic WO3 (Pd/WO3) would possess optimal O2 activation kinetics and an intermediate oxidation/desorption barrier, thereby promoting HCOOH formation. As evidenced by experiments, the Pd/WO3 catalyst achieves an exceptional HCOOH yield of 4.67 mmol gcat-1 h-1 with a high selectivity of 62% under full-spectrum light irradiation at room temperature using molecular O2. Notably, these results significantly outperform the state-of-the-art photocatalytic systems operated under identical condition.

The acidic-free synthesis of 2-nitropyrrole and 2,5-dinitropyrrole using choline nitrate as regent and Pd@C3N4 as photocatalyst

Escaping from conventional hazardous methods, an innovative, acidic-free approach for the synthesis of nitro-heterocycles was realized through photocatalytic nitration using Pd-doped g-C3N4. In this method, chlorate nitrate was initially utilized as a reagent. Spectral analysis and electronic microscopy confirmed the successful doping of Pd nanoparticles (NPs) onto the g-C3N4 surface, which subsequently enhanced the photocatalytic performance. The photogenerated electrons and Pd NPs played pivotal roles in the production of nitro-products. The reactive intermediate, NO2+, derived from nitrate, can be captured and elucidated through the shifts in cyclic voltammetry (CV) curves. Herein, the synthesis of 2-nitropyrrole and 2,5-dinitropyrrole was achieved through the nitration of chlorate nitrate in a friendly manner. Moreover, the composite photocatalyst could be readily isolated and recycled in next four tests, demonstrating its practicality and sustainability in photocatalytic applications.

Revealing the Mechanism of Combining Best Properties of Homogeneous and Heterogeneous Catalysis in Hybrid Pd/NHC Systems

AbstractThe formation of transient hybrid nanoscale metal species from homogeneous molecular precatalysts has been demonstrated by in situ NMR studies of catalytic reactions involving transition metals with N‐heterocyclic carbene ligands (M/NHC). These hybrid structures provide benefits of both molecular complexes and nanoparticles, enhancing the activity, selectivity, flexibility, and regulation of active species. However, they are challenging to identify experimentally due to the unsuitability of standard methods used for homogeneous or heterogeneous catalysis. Utilizing a sophisticated solid‐state NMR technique, we provide evidence for the formation of NHC‐ligated catalytically active Pd nanoparticles (PdNPs) from Pd/NHC complexes during catalysis. The coordination of NHCs via C(NHC)−Pd bonding to the metal surface was first confirmed by observing the Knight shift in the 13C NMR spectrum of the frozen reaction mixture. Computational modeling revealed that as little as few NHC ligands are sufficient for complete ligation of the surface of the formed PdNPs. Catalytic experiments combined with in situ NMR studies confirmed the significant effect of surface covalently bound NHC ligands on the catalytic properties of the PdNPs formed by decomposition of the Pd/NHC complexes. This observation shows the crucial influence of NHC ligands on the activity and stability of nanoparticulate catalytic systems.

Revealing the Mechanism of Combining Best Properties of Homogeneous and Heterogeneous Catalysis in Hybrid Pd/NHC Systems.

The formation of transient hybrid nanoscale metal species from homogeneous molecular precatalysts has been demonstrated by in situ NMR studies of catalytic reactions involving transition metals with N-heterocyclic carbene ligands (M/NHC). These hybrid structures provide benefits of both molecular complexes and nanoparticles, enhancing the activity, selectivity, flexibility, and regulation of active species. However, they are challenging to identify experimentally due to the unsuitability of standard methods used for homogeneous or heterogeneous catalysis. Utilizing a sophisticated solid-state NMR technique, we provide evidence for the formation of NHC-ligated catalytically active Pd nanoparticles (PdNPs) from Pd/NHC complexes during catalysis. The coordination of NHCs via C(NHC)-Pd bonding to the metal surface was first confirmed by observing the Knight shift in the 13C NMR spectrum of the frozen reaction mixture. Computational modeling revealed that as little as few NHC ligands are sufficient for complete ligation of the surface of the formed PdNPs. Catalytic experiments combined with in situ NMR studies confirmed the significant effect of surface covalently bound NHC ligands on the catalytic properties of the PdNPs formed by decomposition of the Pd/NHC complexes. This observation shows the crucial influence of NHC ligands on the activity and stability of nanoparticulate catalytic systems.

N, O Co‐Doping Enhanced Adsorption of Chloramphenicol for Highly Efficient and Robust Electrocatalytic Hydrodechlorination

Comprehensive SummaryElectrocatalysis technology can effectively promote the hydrodechlorination of chloramphenicol (CAP) to reduce the bio‐toxicity. However, there are still some challenges such as low degradation rate and poor stability. Here, we prepared porous N, O co‐doped carbon supported Pd nanoparticles composites (Pd NPs/NO‐C) for electrocatalytic degradation of CAP. The doping of N and O not only effectively enhanced the interaction between substrate and CAP, promoting the mass transfer process, but also enhanced the anchoring effect on Pd nanoparticles, avoiding the occurrence of aggregation. The prepared composites achieved removal efficiency of CAP over 99% within 1 h, and the rate constant was as high as 6.72 h–1, outperforming previous reported electrocatalysts. Additionally, Pd NPs/NO‐C composites showed a wide range of pH tolerance, excellent ion interference resistance and long‐term stability. Our work unravels the importance of mass transfer processes in solution to electrocatalytic hydrodechlorination and provides new research ideas for catalysts design.

Stable Diamine Functionalized Graphene Supported Pd Nanoparticles Showing Excellent Catalytic Activity For Mizoroki–Heck Coupling Reactions

AbstractWe used a simple technique to create palladium nanoparticles on diamine functionalised graphene (Pd(0)‐AAPTMS@G) with an average particle size of 5.5 nm. Our earlier research described the Pd(0)‐AAPTMS@G material as an effective catalyst with outstanding conversion and yields for the Suzuki coupling reaction. We reported the characterisation data for Pd(0)‐AAPTMS@G catalysts previously. Here, we provide a narrative for the excellent selectivity and high yields (92–100 %) for the Mizoroki–Heck coupling product over the same Pd(0)‐AAPTMS@G catalyst. Six uses of the generated catalyst are possible without any activity loss. We also compared the catalyst characterisation for both fresh and reused catalysts.

Solid hydrogen storage with palladium-graphene composites: Synthesis, characterization, and mechanistic insights

Efficient and safe hydrogen storage is a pivotal challenge for the advancement of hydrogen energy technologies. To address this, the engineering of high-performance solid-state hydrogen storage materials through the loading of transition metals (TM) on carbon-based solids has gained considerable interest. However, the mechanics for TM such as Palladium that bolster hydrogen storage have not well addressed yet. This work presents hydrogen absorptions with metal Pd nanoparticles loaded on reduced graphene oxide (Pd-rGO), including material preparation, structural characterization, hydrogen storage performance, and quantum chemical mechanistic insights. A simple material synthesis strategy has been explored and Pd-rGO composites are successfully prepared with graphite powder as raw materials by an easy reduction-oxidation process. Then, Pd-rGO composites are characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman, transmission electron microscopy, and nitrogen adsorption-desorption isotherms methods to clarify the detailed structural characteristics of Pd-rGO with different loading amounts. It is found that Pd nanoparticles with an average particle size of 10 nm are uniformly dispersed on the surface of rGO. The materials have high defect severity and increased specific surface areas with Pd loading. The hydrogen adsorption capacity of Pd-rGO can be increased by 64 % compared with that without Pd loading due to the hydrogen spillover effect. In addition, the intensification mechanism of hydrogen storage of Pd-rGO composites is further understood by using density functional theory calculations and surface interaction analysis.

Green decoration of Pd nanoparticles on MXene/metal organic framework support for photocatalytic degradation of ofloxacin

The widespread use of fluoroquinolone antibiotics, such as ofloxacin (OFL), has led to their unintended presence in aquatic environments. The removal of OFL from water bodies is crucial to mitigate the spread of antibiotic resistance. In this work, palladium nanoparticles supported on MXene/metal organic framework (Pd/MXOF) nanocomposite was successfully prepared via a green approach and then employed as a novel catalyst material for the photocatalytic degradation of OFL. The Pd/MXOF sample demonstrates improved absorption in the visible region in contrast to MXOF samples, possibly attributed to better electronic transfer at catalyst surface. According to experimental results, a higher photocatalytic activity was obtained for Pd/MXOF catalyst in comparison with MXene, MIL-101(Fe), and MXOF substances. Excellent photodegradation efficiency (∼100 %) of OFL after 30 min irradiation of visible light was obtained using Pd/MXOF. The effectiveness degradation of OFL through the suggested photocatalysis process was dependent on the initial concentration of OFL, catalyst dosage, and solution pH value. Following four cycles, the photocatalyst exhibited acceptable stability and reusability. The key roles of hole (h+) and •O2− radical in the photocatalytic reaction were elucidated by the active species trapping studies. This work may provide a very potent strategy to photodegrade antibiotic pollutants in contaminated waters.