Pd Hybrid Research Articles

Electrochemical sensor featuring PdFeCo1−xONPs on carbon paper for the sensitive determination of indole-3-lactic acid levels in serum samples

A highly sensitive and selective electrochemical sensing platform with self-assembled porous 3-D trimetallic (Pd, Fe, and Co) hybrid anchored on a cost-effective and high-conducting carbon paper (CP) synthesized via a facile and cost-effective hydrothermal impregnation and thermal reduction technique was developed for determining indole-3-lactic acid (ILA) levels in buffer and serum samples. Before the analytical phase, the composite (PdFeCo1−xONPs@CP electrode) was thoroughly characterized, and different methods were used to investigate the electrochemical properties. The combination of tri-metallics with CP-fibers improved sensing capacities in the linear range of 0.05–30 μM, with sensitivity and limits of detection of and 0.165 ± 0.013 μA/μM and 7.8 ± 0. 2 nM, respectively, towards ILA determination. Furthermore, the developed sensing platform was utilized for the analyses of ILA in sigma, human normal, and alcohol use disorder patients’ serum samples. Liquid chromatography in tandem with mass spectrometry was equally used to quantify ILA levels in the serum samples and the results of both methods were compared.

Molecular-level insights into surface complexation of arsenite, selenium and cadmium on {2 0 1} TiO2

Arsenic (As) and Selenium (Se) contaminations present an urgent environmental concern, whereas its removal remains a significant challenge due to the lack of fundamental knowledge of the adsorption mechanism and effective adsorbents. Herein, {201} TiO2 exhibited the application potential for As(III) and Se(IV) removal, and the antagonistic effect was examined at the molecular level using X-ray absorption spectroscopy and density functional theory calculations. The Langmuir adsorption capacity of As(III) and Se(IV) on {201} TiO2 was 0.32 mmol/g and 0.25 mmol/g, respectively. The rate constant k for Se(IV) adsorption was 5.46 g/(mmol/h), which was 10.2 times higher than that of As(III) (0.48 g/(mmol/h)). EXAFS and CD-MUSIC results demonstrated that both As(III) and Se(IV) formed bidentate binuclear inner-sphere complexes at the bridge-Ti4C of {201} TiO2. The pd hybrid orbital energy of Ti-O bonds in Ti2O2SeO complex (−2.42 eV) was lower than that in Ti2O2AsO- complex (−2.26 eV), indicating the better adsorption stability and stronger affinity of Se(IV) adsorbed on {201} TiO2. The coexisting Cd(II) formed ternary complexes with As(III)/Se(IV) on {201} TiO2, enhancing the Freundlich adsorption of Se(IV) to 0.69 mmol/g and As(III) to 0.43 mmol/g. The introduction of Cd(II) altered the orbital hybridization interaction, and the charge transfer from Ti-3d to Cd-5s orbitals improved the adsorption energies of As(III)/Se(IV) on {201} TiO2. The ICOHP value of the Se-O-Cd bond was higher than that of the As-O-Cd bond, indicating the stronger affinity of Cd(II) and Se-O dangling bond. Gaining insights into the surface complexation modeling at the molecular and electronic level reveals the nature of coexisting ions adsorption behaviors.

Synergistic photocatalytic nanozymes to promote contaminant removal and hydrogen production

Photocatalytic nanozymes, which combine light-induced redox reactions and enzyme-like catalysis, have emerged as a promising class of nanomaterials. This alliance offers tremendous potential for light-enhanced enzyme-like activity and expands the applications of nanozymes in energy and environmental fields. In this study, a photocatalytic nanozyme OVs-TiO2/Pd hybrid nanosheets (HNSs) with abundant oxygen vacancies (OVs) and controllable Pd components was prepared by a one-step solid-phase reduction method. Benefiting from the synergistic effect and the strong metal-support interaction, OVs-TiO2/Pd HNSs exhibit remarkable light-enhanced oxidase-like and hydrogenase-like activity, they efficiently catalyze the degradation of antibiotics and the production of hydrogen, respectively. Electron spin resonance and transient photovoltage techniques elucidated that the enhanced enzyme-like activities are attributed to the increased generation of charge carriers and reactive oxygen species. This study builds a bridge between photocatalysis and enzyme-like catalysis, opening up a new avenue to explore the multiple functional nanomaterials for a myriad of applications.

Surface-Confined Ultra-Low Scale Pd Engineered Layered Co(OH)2 toward High-Performance Hydrazine Electrooxidation in Alkaline Saline Water.

Applications of abundant seawater in electrochemical energy conversion are constrained due to the sluggish oxygen evolution reaction and the corrosive chlorine oxidation reaction. Hence, it is imperative to develop an efficient anodic reaction alternative suitable for coupling with the cathodic counterpart. Due to a low thermodynamic oxidation potential, hydrazine oxidation reaction (HzOR) offers a unique pathway to overcome these challenges. Herein, spontaneously in situ reduced atomic scale Pd surface-confined to electrochemically prepared layered Co(OH)2 on carbon cloth is synthesized. This study reveals the hydrazine and Pd-dependent morphological evolution of Co(OH)2 and its Pd hybrids into nanoparticulate form. Unlike various layered double hydroxides, Pd integrated Co(OH)2 benefits from the contribution of Co(OH)2 as an active HzOR catalyst and the reductive support to host Pd, resulting in synergistically improved performances. Mass activities of Pd in alkaline and alkaline saline electrolyte are 11.24 and 9.83 A mgPd -1 at 200mV, respectively, corresponding to the highest HzOR activities among noble metals. The optimized Pd hybrid demonstrates ≈6.5 times the current density relative to PtC (14.91mA cm-2 at 200mV) in alkaline saline water with hydrazine. These findings would be beneficial to realize high overpotential anodic alternatives and reduce over-dependence on freshwater for electrocatalysis.

The nanophotonic machinal cavity and its hydrogen sensing application

Hydrogen, a clean energy carrier, possesses great potential to be an alternative fuel in the future. However, it also has a reputation for being explosive and dangerous. Thus, in the realization of hydrogen energy utilization, hydrogen safe storage and transport are the main issues which currently need to be solved at present. For safety, hydrogen leaks or concentration variations should be monitored accurately and timely during storage or transport. Among the many sensors, the optical hydrogen sensor can satisfy demands of safety, online detection, undisturbed surrounding, and lack of spark. Hence, a fiber-based nanophotonic machinal cavity (NPMC) is proposed and proved that it can be used for hydrogen sensing. This cavity is composed of two mirrors: One is fiber-air interface, another is gold (Au)/palladium (Pd) hybrid nanofilm, herein, Au film with low elastic modulus is employed as a reflective mirror and support substrate of Pd component. Since Pd-hydrogen reactions can induce deformation on this hybrid nanofilm, which will change the resonant characteristics of the cavity, Pd functions as hydrogen-sensitive nanomaterial. Experimentally, Au/Pd hybrid nanofilm-based NPMCs are prepared and used to demonstrates the feasibility of hydrogen sensing. The experimental results reveal that this proposed NPMC maintains advantages of reusable, durable, fast response/recovery (12/1s), low limit of detection (0.1%) and widely linear detection range (1–3.5%) in hydrogen sensing application. This intrinsically safe, miniaturized fiber optic device can be used in space constrained and hazardous environments.

Edge engineering of platinum nanoparticles via porphyrin-based ultrathin 2D metal–organic frameworks for enhanced photocatalytic hydrogen generation

Edge-doping engineering in metal nanoparticles (MNPs) is always hard to achieve due to the high surface energy of the hybrid MNPs, while porphyrin-based ultrathin two-dimensional (2D) metal–organic framework (MOF) is demonstrated the positive role in stabilize this structure. Herein, a bottom-up method was developed to prepare platinum nanoparticles (PtNPs)-decorated 2D MOF nanosheets, where a porphyrin ligand of Pd-metalized tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) was applied to synthesize ultrathin MOF nanosheets as Zr-TCPP(Pd) in high yield. Attributing to the high superficial area of ultrathin Zr-TCPP(Pd) nanosheets, Pt NPs can well anchor uniformly with small nanoparticle size to obtain 2% Pt/Zr-TCPP(Pd) hybrid nanosheets, which showed a higher photocatalytic hydrogen production rate of 3348 μmol g-1h−1. This is attributed to the coordination between Zr4+ and C = O of PVP, which promotes the contact between PtNPs and Zr-TCPP(Pd) nanosheets. As a result, the long-life electrons of PdTCPP photosensitizers are rapidly transferred to the electron capture center PtNPs, and the photoelectron-hole recombination is effectively inhibited. The apparent quantum efficiency of 2% Pt/Zr-TCPP(Pd) reaches up to 1.56% at 420 nm. The density functional theory (DFT) calculations revealed the Pd-doped position in Pt79 nanoparticle is important that the Pt78Pdsurf. model (Pd atom was doped on the surface of Pt nanoparticle) showed the highest activity with abundant exposed active region.

Catalytic activity of palladium doped activated carbon from waste coffee on some environmental pollutants

The presence of nitro compounds and such commercial dyes as Congo red, methylene blue, methyl orange and methyl red in water/wastewater causes environmental issues. The treatment of such industrial contaminants, new efficient hybrid catalysts are designed by Research groups all around the world. For this aim, a large of catalyst systems were designed and their water treatment capacities were investigated. As a part of Green Chemistry approach, food wastes could be used for production of porous carbon materials. In this work, a palladium/activated carbon hybrid catalyst (AC–Pd) was prepared and characterized by XRD, SEM/EDS and TEM. It was found from TEM analysis that the average particle size of AC–Pd hybrid was about 54 nm. The reduction capacity of AC–Pd for nitroarenes and organic dyes was investigated by UV–Vis. spectroscopy in aqueous media. According to catalytic tests results, AC–Pd nanocatalyst could be used in reduction of both nitro compounds and organic dyes.

Reduced graphene oxide based hybrid functionalized films for hydrogen detection: Theoretical and experimental studies

In this work, hydrogen sensing characteristics of reduced graphene oxide (rGO) based functional nanomaterials are investigated with first principle calculations and experimental analysis. rGO doped with zinc oxide nanomaterial (i.e. rGO-ZnO), rGO-ZnO with silver nanoparticles (rGO-ZnO-Ag), rGO-ZnO with zirconium oxide (rGO-ZnO-ZrO2), rGO-ZnO doped with silver and palladium (rGO-ZnO-Ag-Pd) are investigated for their sensing capabilities. The influence of gas adsorption on the electronic features of the functional nanostructures are analyzed using the first principles density functional theory. The results of the computation reveal a considerable improvement of graphene oxide sensitivity in the hydrogen gas molecules following hybridization by ZnO, ZnO–Ag, ZnO–Ag–Pd and ZrO2. Fabrication and characterization of aforementioned functional materials and their hydrogen sensing performances are performed and essential sensing characteristics viz., sensitivity, response time, recovery time, reproducibility are also investigated. Out of the fabricated films, rGO-ZnO-Ag-Pd film is found to have the highest sensitivity towards hydrogen. It showed the sensitivity of ∼60% and highest performance factor (evaluated as the ratio of sensitivity to cycle time) among all films, including response time as 10 s and recovery time as 14 s. While performing sensing investigation, the distinct p-type behavior was observed for all the fabricated film. Obtained outcomes relate the promising future of rGO doped ZnO–Ag, ZnO–Ag–Pd and ZrO2 hybrid nano sensor in the advancement of sensitive gas sensors.

Rod-like MnO2 boost Pd/reduced graphene oxide nanocatalyst for ethylene glycol electrooxidation

Anode catalyst is one of the core components of fuel cell, but its poor catalytic activity, short lifespan, and high price are tricky problems to the commercialization of fuel cell. Herein, a novel rod-like MnO2 decorated reduced graphene oxide (RGO) supported Pd hybrid (Pd/RGO-MnO2) has been designed, which manifests more negative onset oxidation potential, higher peak current density, and better long-term stability relative to Pd/RGO and pure Pd catalysts when serving for ethylene glycol electrooxidation. This enhancement may be due to the addition of MnO2, which can effectively promote the adsorption of hydroxyl at a lower potential and produce a strong electronic interaction with Pd, as confirmed by X-ray photoelectron spectroscopy (XPS) technique. In view of its excellent performance and low cost, Pd/RGO-MnO2 is considered to be a potential and effective anode catalyst for DEGFCs.

Semi‐fuzzy CMAC and PD hybrid controller with compressed memory and semi‐regularisation for electric load simulator

Cerebellar model articulation controller (CMAC) and proportional derivative hybrid controller is widely used for torque control in electric load simulator. However, due to some uncertain factors and especially the strong external interference of the surplus torque, the control stability could not be guaranteed. Here, a novel semi-regularised semi-fuzzy CMAC is proposed to get an efficient control effect. This study expands the weight smoothing into a semi-regularisation algorithm, and proves the stability of the hybrid control system based on the stability of the torque motor. To save storage space and reduce computation, the memory space is compressed and a semi-fuzzy mapping rule is proposed to smooth the output of CMAC with a high calculation speed. Both of simulation and experiment results demonstrate that this novel controller could keep stable and reach a good loading accuracy.

Polymer network of graphene oxide with covalently attached 2-(4′-Hydroxyphenyl)fulleropyrrolidine and Palladium: Synthesis, properties and theoretical studies

A new single layer graphene oxide hybrid polymeric material was fabricated in which the fullerene moieties covalently attached to the edges of surface of SLGO sheets were coordinated to palladium atom in an η2-fasion, SLGO-php-C60/Pd. The polymer was characterized by SEM, TEM, FT-IR and Raman techniques. The newly formed material exhibited reversible electrochemical activity in the negative potential range due to the reduction of fullerene cages with an overall electrochemical behavior resembling that of typical organic conducting polymers. The electron density of states calculated using DFT method clearly confirmed the fullerene cage reduction via electron transfer from the low-lying SLGO states. Therefore, coordination polymers of fullerene moieties bonded to the graphene sheets are easier to reduce in comparison to the coordination polymers of pristine C60. In addition, the spectroscopic and electrochemical properties of SLGO-php-C60/Pd hybrid polymeric material were also compared with php-C60/Pd polymer and SLGO-php-C60 hybrid films to seek film morphology-property relations. The present study extends the application of graphene oxide providing electrically conducting, redox-active polymer material for different applications.

Polydopamine Induced in-Situ Formation of Metallic Nanoparticles in Confined Microchannels of Porous Membrane as Flexible Catalytic Reactor.

Oxidant-regulated polymerization of dopamine was exploited, for the first time, for effective surface engineering of the well-defined cylindrical pores of nuclear track-etched membranes (NTEMs) to develop novel catalytic membrane reactor. First, in the presence of a strong oxidant, controlled synthesis of polydopamine (PDA) with tunable particle size was achieved, allowing a homogeneous deposition to the confined pore channels of NTEMs. The PDA interfaces rich in catechol and amine groups provided enhanced hydrophilicity to promote mass transport across the membrane and abundant nucleation sites for formation and stabilization of metallic nanoparticles (NPs). In-situ reductive growth of multiple metallic NPs, including Pd, Ag, and Au, was then achieved inside the cylindrical pores of NTEMs. Using the functionalized membrane as a catalytic reactor, efficient reduction of 4-nitrophenol (4-NP) was demonstrated in a flow-through mode. Moreover, after dissolution removal of the NTEMs, self-sustained one-dimensional (1D) PDA/M (M = Pd, Ag, or Au) hybrid nanotubes (NTs), with determined aspect ratio and a length reaching up to 10 μm, were obtained for catalysis of 4-NP in a batch reaction mode. This study established a facile and versatile method, by rational tuning of the polymerization behavior of dopamine, for effective modification of confined microscale/nanoscale cavities with different surface characteristics. The integration of PDA chemistry with NTEMs would provide more opportunities for development of novel catalytic membrane reactors as well as for the tailored synthesis of functional 1D nanotubes for broadened applications.

Engineering on the edge of Pd nanosheet cocatalysts for enhanced photocatalytic reduction of CO2 to fuels

Edge engineering was performed on Pd nanosheet cocatalysts for enhanced photocatalytic performance of TiO2–Pd hybrid structures in reduction of CO2 to fuels.

Effect of Pt–Pd hybrid nano-particle on CdS's activity for water splitting under visible light

This paper focuses on the bi-metal co-catalyst of CdS in hydrogen generation from water-splitting under visible light. Pt–Pd eutectic alloy NPs was prepared by two-step chemical reduction, and was subsequently loaded on the surface of CdS photo-catalyst by photo-induced electrons when water splitting reaction was occurring under 300 W Xe light (λ > 420 nm). According to the experimental results, the photo-activity is significantly promoted as bi-metal modified on the surface of CdS. The H2 evolution rate of Pt–Pd/CdS, 25.28 mmol/h/gCat., is ca. 2.4 times as much as that of Pt/CdS, and 3.8 times as much as that of Pd/CdS. HRTEM/ED/EDS revealed that the so-obtained Pt–Pd hybrid NPs with a particle size of 5–8 nm is of similar twin structure. XPS revealed that the as-prepared Pt–Pd bi-metal NPs mainly composed of metallic Pt0 and Pd0. UV–Vis diffuse reflectance spectrum of CdS nanoparticles interpreted its trait in visible light adsorption, and PL lifetime indicated that the high active of Pt–Pd/CdS lies in its high separation efficiency.

Au-Pd bimetallic nanoparticles anchored on α-Fe2O3 nonenzymatic hybrid nanoelectrocatalyst for simultaneous electrochemical detection of dopamine and uric acid in the presence of ascorbic acid.

We have found that magnetic α-Fe2O3 nanocubes exhibit an intrinsic catalytic activity toward the electrochemical sensing of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid. Au-Pd bimetallic nanoparticles, which act as efficient signal amplifiers, can be attached to the surface of α-Fe2O3 particles to further enhance the catalytic electrochemical signals. The one-step synthesized α-Fe2O3@Au-Pd hybrid nanostructure shows significantly well-separated oxidation peaks with enhanced peak currents of DA and UA. We then demonstrated the use of this nonenzymatic nanoelectrocatalyst for individual detection, and the linear responses of DA and UA were in the concentration ranges of 100 nM-1 mM and 1 μM-1 mM with detection limits of 1.34 × 10-10 M and 1.8 × 10-6 M (S/N = 3σ/b), respectively. For simultaneous detection, the same detection ranges were retained with significantly lower detection limits of 1.38 × 10-11 M and 597 nM, respectively. The fabricated sensor was finally applied in selectivity tests for the detection of DA and UA with satisfactory results. The practical analytical utility was illustrated by selective measurements of human urine, serum and pharmaceutical drugs without any preliminary treatment.

PVP-crosslinked electrospun membranes with embedded Pd and Cu2O nanoparticles as effective heterogeneous catalytic supports

Palladium(0) (Pd) and copper(I) oxide (Cu2O) nanoparticles (NPs) were successfully embedded in electrospun polyvinylpyrrolidone (PVP) fibrous membranes. The fabrication process involved the synthesis of stable, PVP-capped Pd and Cu2O colloidal hybrid solutions in methanol that on subsequent electrospinning afforded PVP–Pd and PVP–Cu2O fibrous mats. The morphology of the as-prepared nanocomposite fibers was characterised using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed the presence of bead-free, cylindrical fibers with diameters in the submicrometer range while TEM revealed the presence of spherical Pd and Cu2O NPs with diameters below 10 nm that were evenly distributed within the fibers. Thermal treatment of the PVP–Pd and the PVP–Cu2O membranes afforded crosslinked fibrous mats as supported by SEM. Furthermore, the presence of homogeneously distributed Pd and Cu2O NPs within the crosslinked polymer fibers was confirmed by HRTEM/EDX analyses. The above-mentioned nanocomposite fibers demonstrated high catalytic efficacy as heterogeneous catalytic supports in Heck, Suzuki (PVP–Pd) and click (PVP–Cu2O) reactions. Finally, the reusability of the membranes was briefly investigated with up to three consecutive runs being effective.

Spillover enhanced hydrogen uptake of Pt/Pd doped corncob-derived activated carbon with ultra-high surface area at high pressure

Corncob-derived activated carbon (CAC) was prepared by potassium hydroxide activation. The Pt/Pd-doped CAC samples were prepared by two-step reduction method (ethylene glycol reduction plus hydrogen reduction). The as-obtained samples were characterized by N2-sorption, TEM and XRD. The results show the texture of CAC is varied after doping Pt/Pd. The Pd particles are easier to grow up than Pt particles on the surface of activated carbon. For containing Pt samples, the pore size distributions are different from original sample and Pd loaded sample. The hydrogen uptake results show excess hydrogen uptake capacity on the Pt/Pd-doped CAC samples are higher than pure CAC at 298 K, which should be attributed to hydrogen spillover effects. The 2.5%Pt and 2.5%Pd hybrid doped CAC sample shows the highest hydrogen uptake capacity (1.65 wt%) at 298 K and 180 bar, The particle size and distribution of Pt/Pd catalysts could play a crucial role on hydrogen uptake by spillover. The total hydrogen storage capacity analysis show that total H2 storage capacities for all samples are similar, and spillover enhanced H2 uptakes of metal-doped samples could not well support total H2 storage capacity. The total pore volume of porous materials also is a key factor to affect total hydrogen storage capacity.

A Well‐Defined Pd Hybrid Material for the Z‐Selective Semihydrogenation of Alkynes Characterized at the Molecular Level by DNP SENS

Direct evidence of the conformation of a Pd-N heterocyclic carbene (NHC) moiety imbedded in a hybrid material and of the Pd-NHC bond were obtained by dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) at natural abundance in short experimental times (hours). Overall, this silica-based hybrid material containing well-defined Pd-NHC sites in a uniform environment displays high activity and selectivity in the semihydrogenation of alkynes into Z-alkenes (see figure).

Size-controllable preparation of palladium nanoparticles assembled on TiO2/graphene nanosheets and their electrocatalytic activity for glucose biosensing

In this work, for the first time, size-controllable preparation of Pd nanoparticles assembled on graphene was realized through UV reduction by TiO2. Firstly, a hybrid nanocomposite of graphene/TiO2 (GT) was synthesized via a reported one-pot water-phase approach. It was interesting to find that when altering the additive volume of TiCl3 (reductant) in the reaction system (e.g., 0.6, 1.2, 1.8, 2.4 and 3.0 mL), the morphology of TiO2 on graphene sheets also changed, from particle to irregular rod-like. Then, these GTx nanocomposites were further employed as supporting materials for the reduction and dispersion of Pd nanoparticles (NPs). The photogenerated electrons from UV-irradiated TiO2 are transported across the GTx composites to stepwise reduce Pd2+ to Pd NPs. Our results demonstrated that the diameters of these as-prepared Pd NPs showed a similar GTx-dependent behavior, ranging from 4.5 ± 0.8 to 5.8 ± 0.9 nm. Finally, using H2O2 as the electrochemical probe, the five resultant GTx–Pd hybrid nanocomposites displayed distinct electrocatalytic activity to H2O2 as a function of the feeding volume of TiCl3. The above hybrid nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, etc. More importantly, a novel glucose biosensor with high sensitivity and selectivity was accordingly fabricated by a layer-by-layer method, which facilitates the fast electron transfer of glucose oxidase at graphene-based films because of the excellent electroactivity of GT1.2–Pd hybrids.

The dual role of Zn–acid medium for one-step rapid synthesis of M@rGO (M = Au, Pt, Pd and Ag) hybrid nanostructures at room temperature

We report a new protocol for the synthesis of M@rGO (M = Au, Pt, Pd, Ag and rGO = reduced graphene oxide) hybrid nanostructures at room temperature in Zn-acid medium. The roles of Zn-acid are to reduce the GO by generated hydrogen and the deposition of metal nanoparticles on rGO by galvanic replacement reaction between Zn and M(n+).