Mesoporous Pd Research Articles

Solvothermal Fabrication of Mesoporous Pd Nano-Corals at Mild Temperature for Alkaline Hydrogen Evolution Reaction.

Porous metallic nanomaterials exhibit interesting physical and chemical properties, and are widely used in various fields. Traditional fabrication techniques are limited to metallurgy, sintering, electrodeposition, etc., which limit the control of pore size and distribution, and make it difficult to achieve materials with high surface areas. On the other hand, the chemical preparation of metallic nanoparticles is usually carried out with strong reducing agents or at high temperature, resulting in the formation of dispersed particles which cannot evolve into porous metal. In this study, we reported the simple fabrication of coral-like mesoporous Pd nanomaterial (Pd NC) with a ligament size of 4.1 nm. The fabrication was carried out by simple solvothermal reduction at a mild temperature of 135 °C, without using any templates. The control experiments suggested that tetrabutylammonium bromide (TBAB) played a critical role in the Pd(II) reduction into Pd nanoclusters and their subsequent aggregation to form Pd NC, and another key point for the formation of Pd NC is not to use a strong reducing agent. In alkaline water electrolysis, the Pd NC outperforms the monodisperse Pd NPs and the state-of-the-art Pt (under large potentials) for H2 evolution reaction, probably due to its mesoporous structure and large surface area. This work reports a simple and novel method for producing porous metallic nanomaterials with a high utilization efficiency of metal atoms, and it is expected to contribute to the practical preparation of porous metallic nanomaterials by solvothermal reductions.

Heterogeneous Pd-PdO mesoporous film for ammonia electrosynthesis

Exploring cost-effective and highly active electrocatalysts is of great significance for sustainable electrochemical NH3 synthesis. Palladium (Pd)-based catalysts have been unanimously considered as one of the most efficient catalysts for the nitrogen reduction reaction (NRR). Herein, self-supported mesoporous Pd film with partial oxidation on Ni foam (mPd-PdO/NF) was synthesized through the micelle-assisted chemical replacement method coupled with air oxidation under 260 °C, and the mPd-PdO/NF electrocatalyst exhibited superior NRR performance with the maximum values of r NH3 (24.8 mg h−1 mgcat. −1) and FE (16.64%) were obtained at −0.1 V, relative to the single counterparts (mPd/NF and mPdO/NF). It is proposed that both metallic Pd and its oxide domains when co-existing with a phase boundary between them can facilitate nitrogen activation and hydrogenation, resulting in an enhanced NRR performance. This work provides an inspiring strategy for the rational design of highly active and durable metal–metal–oxide nanoarchitectonics for ammonia electrosynthesis.

Mechanistic insight into deep holes from interband transitions in Palladium nanoparticle photocatalysts

SummaryUtilizing hot electrons generated from localized surface plasmon resonance is of widespread interest in the photocatalysis of metallic nanoparticles. However, hot holes, especially generated from interband transitions, have not been fully explored for photocatalysis yet. In this study, a photocatalyzed Suzuki-Miyaura reaction using mesoporous Pd nanoparticle photocatalyst served as a model to study the role of hot holes. Quantum yields of the photocatalysts increase under shorter wavelength excitations and correlate to “deeper” energy of the holes from the Fermi level. This work suggests that deeper holes in the d-band catalyze the oxidative addition of aryl halide R-X onto Pd0 at the nanoparticles' surface to form R-PdII-X complex, thus accelerating the rate-determining step of the catalytic cycle. The hot electrons do not play a decisive role. In the future, catalytic mechanisms induced by deep holes should deserve as much attention as the well-known hot electron transfer mechanism.

PdNi/Ni Nanotubes Assembled by Mesoporous Nanoparticles for Efficient Alkaline Ethanol Oxidation Reaction.

The optimization of structure and composition is essential to improve the performance of catalysts. Herein, mesoporous nanoparticles assembled PdNi/Ni nanotubes (mPdNi/Ni NTs) are successfully fabricated using nickel nanowires as sacrificial template. The combination of nanotubular structure with mesoporous nanoparticle morphology can provide facilitated transfer channels and sufficient active sites, allowing the full contact and reaction between catalysts and reactants. Therefore, the synthesized mPdNi/Ni NTs exhibite superior ethanol oxidation performance to mesoporous Pd nanotubes and commercial Pd black. This study proposes a rational strategy for the development of nanoparticle assembled nanotubes with surface mesoporous morphology, which can greatly improve catalytic performance in various electrocatalytic fields.

Porosity and thickness effect of Pd–Cu–Si metallic glasses on electrocatalytic hydrogen production and storage

This contribution places emphasis on tuning pore architecture and film thickness of mesoporous Pd–Cu–Si thin films sputtered on Si/SiO2 substrates for enhanced electrocatalytic and hydrogen sorption/desorption activity and their comparison with the state-of-the-art thin film electrocatalysts. Small Tafel slope of 43 mV dec–1 for 1250 nm thick coating on 2 µm diameter pores with 4.2 µm interspacing electrocatalyst with comparable hydrogen overpotentials to the literature suggests its use for standard fuel cells. The largest hydrogen sorption has been attained for the 250 nm thick electrocatalyst on 5 µm pore diameter with 12 µm interspacing (2189 µC cm−2 per CV cycle), making it possible for rapid storage systems. Moreover, the charge transfer resistance described by an equivalent circuit model has an excellent correlation with Tafel slopes. Along with its very low Tafel slope of 42 mV dec–1 10 nm thick electrocatalyst on 2 µm diameter pores with 4.2 µm interspacing has the highest capacitive response of ∼ 0.001 S sn cm−2 and is promising to be used as a nano-charger and hydrogen sensor. The findings of Si/SiO2 supported mesoporous Pd-based metallic glass (MG) assemblies suggest a similar design applicability for crystalline systems and other MG types.

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO 2 Reduction

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO ₂ Reduction

Decolorizing brilliant green by mesoporous Pd–Fe magnetic nanoparticles immobilized on reduced graphene oxide: artificial neural network modeling

The mesoporous Pd–Fe magnetic nanoparticles immobilized on the reduced graphene oxide were employed in the present work for the decolorization of toxic brilliant green in aqueous phase. The decolorization process was modeled using backpropagation artificial neural network and optimized by genetic algorithm and particle swarm optimization. These magnetic nanocomposites were synthesized by the two-step reaction in aqueous phase method and then characterized with various methods. According to response surface methodology, the effect of operating parameters on the decolorization of brilliant green in aqueous solution was studied through batch experiments. On the basis of these experiments, the prediction ability of response surface methodology and backpropagation neural network method was assessed. The decolorization process follows Freundlich isotherm and pseudo-second-order kinetics. Furthermore, thermodynamics studies demonstrate that the adsorption of brilliant green onto the nanocomposites was endothermic and spontaneous. Overall, these mesoporous nanomaterials have the advantages of strong adsorption capacity and fast decolorization for brilliant green, and modeling of the removal process with artificial neural network was successful.

Hydrogen Evolution Activity of Mesoporous Pd-Based Metallic Glass Assemblies with Tunable Pore Architecture and Film Thickness

The necessity for efficient green energy production compels scientists to develop advanced nanostructured metallic alloys with tunable properties. This contribution places emphasis on tuning pore architecture and film thickness of mesoporous Pd – Cu – Si thin films sputtered on Si substrates for enhanced electrocatalytic and hydrogen sorption/desorption activity and their comparison with the state-of-the-art electrocatalysts. The small Tafel slope of 44 mV dec–1 with a rapid rise in the cathodic current rendering low hydrogen overpotentials of 24 mV at 10 mA cm–2, and the largest sorption/desorption peaks for the T4H2 electrode suggest its use for a fuel cell electrode. Moreover, the kinetic parameters described by the equivalent circuit model have a very good correlation with Tafel slopes and sample mass. The 10 nm T1H1 sample has one of the highest capacitive responses where the hydrogen-metal interaction takes place and is promising as a nano-charger and sensing of hydrogen.

Organotrialkoxysilane-functionalized mesoporous Pd–Ni nanocatalyst for selective hydrazine decomposition and sensing

Organotrialkoxysilanes, particularly amino-glycidoxy and epoxy-functionalized alkoxysilanes, allow for the controlled synthesis of noble metal nanoparticles and bimetallic nanoparticles; these materials enable a concentration-dependent enhancement in resonance Rayleigh scattering, which may be useful for the selective detection of hydrazine. 3-aminopropyltrimethoxysilane (3-APTMS)-treated gold cations were converted into gold nanoparticles within a few seconds (< 1 min) in the presence of 3-glycidoxypropylytrimethoxysilane (3-GPTMS). Organotrialkoxysilane-functionalized gold nanoparticles that exhibit an average size of 9 nm or 17 nm were processed and evaluated for synchronous fluorescence-based detection of hydrazine. Organotrialkoxysilane allowed the formation of nickel–palladium bimetallic nanocrystallite-supported mesoporous silica nanoparticles. Organotrialkoxysilane served as a template for the stabilization and formation of bimetallic Pd–Ni nanocrystallites within a mesoporous silica nanoparticle (MSNP) support. The as-made heterogeneous support enabled real-time degradation of hydrazine.

Synthesis and Crystal-Phase Engineering of Mesoporous Palladium-Boron Alloy Nanoparticles.

Rational design and synthesis of noble metal nanomaterials with desired crystal phases (atomic level) and controllable structures/morphologies (mesoscopic level) are paramount for modulating their physiochemical properties. However, it is challenging to simultaneously explore atomic crystal-phase structures and ordered mesoscopic morphologies. Here, we report a simple synergistic templating strategy for the preparation of palladium–boron (Pd–B) nanoparticles with precisely controllable crystal-phases and highly ordered mesostructures. The engineering of crystal-phase structures at atomic levels is achieved by interstitially inserting metallic B atoms into face-centered cubic mesoporous Pd (fcc-mesoPd) confined in a mesoporous silica template. With the gradual insertion of B atoms, fcc-mesoPd is transformed into fcc-mesoPd5B, hcp-mesoPd2B with randomly distributed B atoms (hcp-mesoPd2B-r), and hcp-mesoPd2B with an atomically ordered B sequence (hcp-mesoPd2B-o) while preserving well-defined mesostructures. This synergistic templating strategy can be extended to engineer crystal-phase structures with various mesostructures/morphologies, including nanoparticles, nanobundles, and nanorods. Moreover, we investigate the crystal-phase-dependent catalytic performance toward the reduction reaction of p-nitrophenol and find that hcp-mesoPd2B-o displays much better catalytic activity. This work thus paves a new way for the synthesis of hcp-Pd2B nanomaterials with mesoscopically ordered structure/morphology and offers new insights of fcc-to-hcp evolution mechanisms which could be applied on other noble metal-based nanomaterials for various targeted applications.

Correction: Cubic mesoporous Pd–WO3 loaded graphitic carbon nitride (g-CN) nanohybrids: highly sensitive and temperature dependent VOC sensors

Correction for ‘Cubic mesoporous Pd–WO3 loaded graphitic carbon nitride (g-CN) nanohybrids: highly sensitive and temperature dependent VOC sensors’ by Ritu Malik et al., J. Mater. Chem. A, 2018, 6, 10718–10730, DOI: 10.1039/C8TA02702A.

Hierarchical architectures of mesoporous Pd on highly ordered TiO2 nanotube arrays for electrochemical CO2 reduction

A novel hierarchical structure was achieved by pulsed electrodeposition of mesoporous Pd onto highly ordered TiO2 nanotube arrays. We examined the implications of mass transfer limitations of this architecture towards product selectivity of CO2 electroreduction.

Tailored Design of Mesoporous PdCu Nanospheres with Different Compositions Using Polymeric Micelles.

Mesoporous metals have attracted a lot of interest due to their wide range of applications, particularly in catalysis. We previously reported the preparation of mesoporous Pd using block copolymer micelle templates (Chem. Sci. 2019, 10, 4054). Here we extend this synthetic concept to generate alloyed spherical palladium-copper (PdCu) nanoparticles with an open porous network and uniform morphology. This one-pot synthesis is initiated by water-induced micellization of the block copolymer, followed by the chemical reduction, nucleation, and growth of mesoporous spherical alloy nanoparticles. Porosity enables accessibility to numerous active sites throughout the interior and exterior surfaces of the nanoparticles. Mesoporous nanoparticles composed of Pd and Cu alloy exhibit enhanced electrocatalytic activity and stability in the ethanol oxidation reaction (EOR) and the oxygen reduction reaction (ORR).

Mesoporous Pd|β-SiCNW-nC based home made screen printed electrode for high sensitive detection of hydrazine

β-SiC nanowires (β-SiCNWs) were synthesized by using a simple method and employed for fabricating β-SiCNW-nC hybrid catalyst support. Next, palladium (Pd) nanoparticles were deposited at the surface of the support by using chemical reduction method. The synthesized Pd|β-SiCNW-nC mesoporous electrocatalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV) and N2 adsorption-desorption experiment. The results indicated that Pd nanoparticles are uniformly deposited at the surface of hybrid support with an average size of 50 nm. The synthesized catalyst was uniformly screen printed on glass electrode by using a novel, simple and cheap method (Pd|β-SiCNW-nC|SPE). The constructed SPE was used for hydrazine detection in real samples. The Pd|β-SiCNW-nC|SPE showed good stability and high electrocatalytic activity for hydrazine oxidation. The limit of detection (S/N = 3) and sensitivity were found to be 0.012 μM and 0.725 μA/μM, respectively.

Pore-tuning to boost the electrocatalytic activity of polymeric micelle-templated mesoporous Pd nanoparticles.

Understanding how mesoporous noble metal architectures affect electrocatalytic performance is very important for the rational design and preparation of high-performance electrocatalysts. Herein, by using polymeric micelle-assembled structures as templates, mesoporous Pd nanoparticles with tunable porous constructions are synthesized by simply tuning the solvent compositions. The effect of porous Pd nanoparticles on the electrocatalytic performance is thoroughly studied. Their superior electrocatalytic activity can be attributed to the mass transport efficiency and open porous structures.

Continuous mesoporous Pd films with tunable pore sizes through polymeric micelle-assisted assembly

The fabrication of continuous mesoporous Pd films with larger open pores and tunable pore sizes have been successfully demonstrated via a facile polymeric micelle-assisted electrochemical deposition.

Synthesis and characterization of mesoporous Pd(II) organometal nanoplatelet catalyst for copper-free Sonogashira reaction in water

Periodic mesoporous organopalladium(II)-bridged silica with platelet morphology (Pd(II)-PMO-P) was synthesized by the co-condensation of TEOS and Pd[PPh2(CH2)2Si(OC2H5)3]2Cl2 using P123 as structure-directing agent. The as-made Pd(II)-PMO-P samples were characterized with XRD, BET, ICP, SEM, TEM, solid NMR, XPS, as well as FT-IR. It was found that these products were composed of platelets (300–400 nm) with short and straight mesoporous channels (100–200 nm). Organopalladium (II) was integrally incorporated into the walls of silica. Compared to the organopalladium(II)-bridged PMO with irregular pore structure, Pd(II)-PMO-P catalyst exhibited high catalytic efficiency in the water-medium Sonogashira reaction because its short pore channels and nano-sized structures could accelerate the diffusion and adsorption of reactant molecules. Furthermore, the heterogeneous catalyst could be reused several times without significant loss of activity, which efficiently decreases the cost as well as the pollution in order to meet the criteria of green chemistry.

Nafion®-coated mesoporous Pd film toward remarkably enhanced detection of lactic acid.

Mesoporous metal films can detect biomarkers with high sensitivity. Further coating the mesoporous metal with polymers enhances sensing selectivity by favoring specific biomarkers against other interferents. In the present study, we report the fabrication of a Nafion®-coated mesoporous Pd film to filtrate interferents present in sweat during non-invasive biosensing. By using a Nafion®-coated mesoporous Pd film, lactic acid, a metabolite present in sweat, can be successfully detected with high sensitivity.

Continuous Mesoporous Pd Films by Electrochemical Deposition in Nonionic Micellar Solution

Mesoporous metals that combine catalytic activity and high surface area can provide more opportunities for electrochemical applications. Various synthetic methods, including hard and soft templating, have been developed to prepare mesoporous/nanoporous metals. Micelle assembly, typically involved in soft-templates, is flexible and convenient for such purposes. It is, however, difficult to control, and the ordering is significantly destroyed during the metal deposition process, which is detrimental when it comes to designing precisely mesostructured materials. In the present work, mesoporous Pd films were uniformly electrodeposited using a nonionic surfactant, triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), as a pore-directing agent. The interaction between micelles and metal precursors greatly influences the metal growth and determines the final structure. The water-coordinated species interact with the ethylene oxide moiety of the micelles to effectively drive the ...

Layer‐by‐Layer Motif Architectures: Programmed Electrochemical Syntheses of Multilayer Mesoporous Metallic Films with Uniformly Sized Pores

AbstractAlthough multilayer films have been extensively reported, most compositions have been limited to non‐catalytically active materials (e.g. polymers, proteins, lipids, or nucleic acids). Herein, we report the preparation of binder‐free multilayer metallic mesoporous films with sufficient accessibility for high electrocatalytic activity by using a programmed electrochemical strategy. By precisely tuning the deposition potential and duration, multilayer mesoporous architectures consisting of alternating mesoporous Pd layers and mesoporous PdPt layers with controlled layer thicknesses can be synthesized within a single electrolyte, containing polymeric micelles as soft templates. This novel architecture, combining the advantages of bimetallic alloys, multilayer architectures, and mesoporous structures, exhibits high electrocatalytic activity for both the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR).