Reduction Of Pd Research Articles

Boosting alkyne semi-hydrogenation selectivity via metal-organic interface modulated self-supporting palladium-based catalysts

The semi-hydrogenation of alkynes is crucial in the chemical industry, yet developing catalysts with both high activity and selectivity remains challenging. In this work, we introduced a self-supported method to fabricate a palladium-based nanocatalyst by in-situ reduction of Pd(II) on copper-based coordination polymers (Cu(I)-PNS) without external reducing agents. The resulting Pd/Cu(I)-PNS catalyst demonstrated exceptional efficiency and 94.8 % selectivity for styrene in the semi-hydrogenation of phenylacetylene, with no over-hydrogenation. Our findings highlight that the metal–organic interface enhances the catalyst’s selectivity by weakening styrene adsorption due to electronic modification. Additionally, the catalyst exhibited superior stability and activity, showing potential for various alkynes. This approach offers a direct and efficient strategy for creating highly selective palladium-based nanocatalysts for industrial applications.

Influence of iron content in palladium catalysts supported on alumina and their reduction conditions on the hydrodechlorination of diclofenac in aqueous solutions

Using the method of wet impregnation of alumina with iron and palladium nitrates, 1Pd0.5Fe and 1Pd10Fe catalysts modified with iron oxides were prepared with a target content of 1 wt % Pd, 0.5 or 10 wt % iron. The catalysts were compared with each other and with the monometallic catalyst 1Pd in the hydrodechlorination (HDC) of diclofenac (DCF) in dilute aqueous solutions at 30°C in batch and flow reactors after high-temperature (320°C) and mild (30°C) reduction; the latter was carried out in a batch or flow reactor. Using X-ray photoelectron spectroscopy (XPS), it was shown that after reduction at 320°C the surface of catalysts contains mainly Pd0, Fe2+ and Fe3+. The surface Fe2+/Fe3+ ratio increases as the iron content decreases. The reduction of Pd2+ to Pd0 is possible already at 30°C, but it proceeds much worse on the surface of 1Pd0.5Fe compared to 1Pd10Fe. According to XPS data, temperature-programmed reduction and infrared spectroscopy of diffuse reflection of adsorbed CO, modification with iron oxides increases the palladium content on the surface compared to 1Pd, promotes the emergence of new Pd–O–Fe centers, and affects the ability of palladium to be reduced. These effects increase with increasing iron content. Iron-modified catalysts reduced at 320°C showed similar activity and stability in the conversion of DCP in flow-through and batch systems. Unlike 1Pd0.5Fe, the 1Pd10Fe catalyst is highly efficient and stable even after mild reduction at 30°C. Under flow conditions with comparable DCF conversion, it provides increased selectivity in the HDC reaction of diclofenac compared to 1Pd, which is also active in hydrogenation.

Dynamic detection of soluble intermediates during methanol electrooxidation

Methanol electrooxidation at a Pt band electrode is studied in a microfluidic flow cell (MFFC) with simultaneous electrochemical detection of formic acid at a down-stream sensor (detector) Pd electrode. Detection of formic acid at the Pd electrode is possible through either a fast voltammetry or a potential step procedure. In both cases, maximizing the detection signal (oxidation current) requires Pd oxide formation and reduction before detection. Pd oxide formation is needed to oxidize surface-bound carbonaceous species while Pd oxide reduction is needed to reactivate the electrode surface. Although formic acid alone is easily detected and provides a stable detection signal at the Pd sensor electrode, simultaneous formation of formaldehyde during methanol oxidation degrades the detection signal at the Pd electrode over time. We show that dynamic detection of sub-millimolar formic acid concentrations in 2M methanol is possible at a time resolution down to 2 s. Dynamic detection during methanol oxidation at platinum shows that production of soluble intermediates occurs at all potentials where an oxidation current is observed. Furthermore, a higher faradaic efficiency to formic acid occurs during the main methanol oxidation peak in the positive-going sweep compared to the negative-going sweep, and is higher still at potentials above 1V. This work shows that microfluidic flow cells can be used for fast and dynamic detection of soluble reaction intermediates by using down-stream electrodes with custom potential step or sweep sequences.

Synthesis of Palladium Nanomaterials Using Plant Leaf Extract and their Enhanced Photocatalytic Activities against Organic Dyes

Aims and Objectives: This study aimed to carry out the green synthesis of palladium nanoparticles (Pd NPs) using the aqueous leaves extract of Eclipta alba. The appearance of a characteristic surface plasmon resonance peak at 410 nm confirmed the synthesis of Pd NPs. Method: The average particle sizes of 13 nm were observed by using the leaf concentrations of 10 mL with a certain amount of PdCl2 (0.001 M) at 25 ̊ C. The Pd NPs, as synthesized under the optimized conditions (10 mL extract + 60 ̊ C + 0.001 M PdCl2), were spherical in shape, small in size, and uniformly distributed, as depicted by HR-TEM images. Results: FTIR, XRD, DLS, and zeta potential further confirmed the formation of Pd NPs. The Pd NPs synthesized at optimized conditions exhibited strong catalytic activity in dye Eosin yellow, Rose Bengal, Tartrazine, and Ponceau S degradation by discoloration of dyes in 3 hrs. The removal of all dyes by the Pd NPs was optimized by varying specific operating parameters, such as initial dye concentration, solution pH, irradiation time, and temperature. Conclusion: This high activity of Pd NPs may be due to their small size, high dispersion, and surface- capping phytochemicals. result: Bio-fabrication of metallic Pd NPs using different plant extracts compared to other reducing agents is more scalable, rapid, and cost-effective for generating bulk nanoparticles. The phytochemical principles, such as phytoconstituents, reduce the PdCl2 to Pd NPs and are implicated in the capping and stability of the nanoparticles. Hence, the leaves of Eclipta alba have different polyols and are well known. Apart from this, hydroxyl groups in phenolic compounds may participate in the bio-reduction of PdCl2. Such compounds can chelate metal ions to form their quinones form, which is an intermediate palladium complex. Then, stabilization of the intermediate form and reduction of Pd2+ to Pd0 occurred due to free electrons or nascent hydrogen produced during the bio-reduction reaction. Finally, Pd-NPs were prepared due to the collision of neighboring Pd0 atoms. These significant conjugations exist in the keto-enol system within the quinone form of the compound.

Non-surgical treatment of residual periodontal pockets using sodium hypochlorite/amino acid gel and cross-linked hyaluronic acid—a 9-month pilot randomized controlled clinical trial

ObjectivesThis pilot randomized controlled clinical trial compares the clinical outcome obtained in persistent periodontal pockets during 9-month follow-up of supportive periodontal step 4 treatment performed by either combining subgingival instrumentation with adjunctively used sodium hypochlorite/amino acid gel and crosslinked hyaluronic acid (xHyA) or subgingival instrumentation alone.Materials and methodsStudy protocol is registered under NCT06438354 at Clinicaltrials.gov. Patients seeking further therapy after completed step 2 non-surgical periodontal treatment underwent either repeated subgingival instrumentation with adjunctive application of sodium hypochlorite/amino acid gel and crosslinked hyaluronic acid (group A) or repeated subgingival instrumentation alone (group B). One calibrated investigator performed the treatment sequence in both groups accordingly. Subgingival instrumentation of the residual pockets was carried out under local anaesthesia using hand- and ultrasonic instruments, as well as air polishing in both groups. Patients were instructed to continue oral hygiene without any restriction. At 3-month re-evaluation treatment was repeated accordingly at sites with persistent 5 mm probing depth and BoP + . Clinical attachment level (CAL), pocket probing depth (PPD), gingival recession (GR), and bleeding on probing (BoP) were recorded at baseline (T1), 3- (T2) and 9-month (T3) post-op, with CAL as a primary outcome measure.ResultsIn total 52 patients (20 females and 32 males, mean age 58.4 ± 2.4 years) presenting with 1448 sites which required further periodontal treatment were enrolled. Both groups exhibited homogeneity in terms of age, gender, smoking habit, initial number of sites, and BOP. At 9-month evaluation, PD reduction and CAL gain showed significant differences between the test and control group, favouring the adjunctive treatment. GR tended to exhibit more recovery in the test group compared to the control group. Although BOP frequency effectively reduced in both groups, there was no statistically significant difference between the two groups.ConclusionWithin the limits of the study, the present data indicates that, during subgingival instrumentation of persistent pockets, the adjunctive usage of sodium hypochlorite/amino acid gel and xHyA sufficiently improves the clinical outcomes. The continuous improvement of CAL in association with the GR scores observed in group A, indicates that sites subjected to adjunctive treatment may indicate a tendency for a regenerative response to treatment within the 9-month follow-up period.

Pd(0)/Xantphos-Catalyzed Benzylic C(sp3)-O Arylation of Benzyl Heteroaryl Ethers: Reduction of Pd(II) to Pd(0) by Xantphos.

Herein, we report the synthesis of 1,1-diarylmethanes via palladium-catalyzed benzylic C(sp3)-O arylation of benzyl alcohol derivatives. An efficient, straightforward approach to synthesizing Pd(0)(xantphos)2 was developed through in situ reduction of Pd(II) to Pd(0) with the bidentate tertiary phosphine xantphos, which proved to be a highly active precatalyst in the Suzuki-Miyaura cross-coupling reaction of benzyl heteroaryl ethers.

Clinical outcomes of inferior oblique myectomy in age categorized patients with unilateral superior oblique palsy

BackgroundUnilateral superior oblique palsy (SOP) is the most common isolated cranial nerve palsy. This report looks at the results and safety of inferior oblique (IO) myectomy for SOP. MethodsA retrospective chart review of patients with fusional ability who underwent IO myectomy for unilateral SOP over a 15-year period, at one of our university-associated health care centers. Primary outcomes were: distance hypertropia and excyclotropia in primary position, inferior oblique overaction (IOOA) and the correlation between the age at surgery and the residual distance hypertropia. ResultsA total of 73 patients with unilateral SOP who underwent IO myectomy were included in the analysis. Mean pre-operative values were: distance hypertropia: 15.41 ± 6.8 Prism Diopters (range 4–30 PD), IOOA: +2.2 ± 0.7 (range 0–3.5) and excyclotropia: +5.34 ± 3.6° (range 0–12°). Mean post-operative values were: distance hypertropia: 3.7 ± 3.4PD [0-14PD], IOOA: −0.1 ± 0.8 [(-2)-2] and excyclotropia: +1.1 ± 2.3°[(-5)-10]. The younger age group (0–20 years old) had a trend toward smaller preoperative distance hypertropia (P = 0.051), and a significantly smaller distance hypertropia post-operatively (p = 0.007). There was no case of ocular complication. ConclusionsOn average, IO myectomy results in a 11.7PD reduction of the distance hypertropia, and 4° reduction of excyclotropia, with an effective reduction of IOOA. While these results are comparable to other surgical methods reported in the literature, they underline an efficacy without the risks of complications such as anti-elevation syndrome and possible scleral perforation. The younger age group had a trend toward smaller preoperative deviation, and better outcomes compared to the older age group.

Study on the Gas-Chromic Character of Pd/TiO2 for Fast Room-Temperature CO Detection.

As a widely used support, TiO2 has often been combined with Pd to form highly sensitive gas-chromic materials. Herein, we prepared a series of Pd/TiO2 catalysts with different Pd content (from 0.1 to 5 wt.%) by the impregnation method for their utilization in fast room-temperature CO detection. The detection was simply based on visible color change when the Pd/TiO2 was exposed to CO. The sample with 1 wt.% Pd/TiO2 presented an excellent CO gasochromic character, associated with a maximum chromatic aberration value of 90 before and after CO exposure. Systematic catalyst characterizations of XPS, FT-IR, CO-TPD, and N2 adsorption-desorption and density functional theory calculations for the CO adsorption and charge transfer over the Pd and PdO surfaces were further carried out. It was found that the interaction between CO and the Pd surface was strong, associated with a large adsorption energy of -1.99 eV and charge transfer of 0.196 e. The color change was caused by a reduction in Pd2+ to metallic Pd0 over the Pd/TiO2 surface after CO exposure.

Restructuring dynamics of surface species in bimetallic nanoparticles probed by modulation excitation spectroscopy

Restructuring of metal components on bimetallic nanoparticle surfaces in response to the changes in reactive environment is a ubiquitous phenomenon whose potential for the design of tunable catalysts is underexplored. The main challenge is the lack of knowledge of the structure, composition, and evolution of species on the nanoparticle surfaces during reaction. We apply a modulation excitation approach to the X-ray absorption spectroscopy of the 30 atomic % Pd in Au supported nanocatalysts via the gas (H2 and O2) concentration modulation. For interpreting restructuring kinetics, we correlate the phase-sensitive detection with the time-domain analysis aided by a denoising algorithm. Here we show that the surface and near-surface species such as Pd oxides and atomically dispersed Pd restructured periodically, featuring different time delays. We propose a model that Pd oxide formation is preceded by the build-up of Pd regions caused by oxygen-driven segregation of Pd atoms towards the surface. During the H2 pulse, rapid reduction and dissolution of Pd follows an induction period which we attribute to H2 dissociation. Periodic perturbations of nanocatalysts by gases can, therefore, enable variations in the stoichiometry of the surface and near-surface oxides and dynamically tune the degree of oxidation/reduction of metals at/near the catalyst surface.

Non-surgical retreatment versus papillary preservation flap surgery for residual pockets: A randomized controlled trial with clinical and patient-reported outcomes.

To compare the efficacy of non-surgical re-instrumentation (NSR) and papillary preservation flap (PPF) surgery at single-rooted teeth with residual pockets. Patients with at least a residual pocket depth (PD ≥ 5 mm) after Steps I and II were enrolled and randomly assigned to receive NSR or PPF surgery. The primary outcome was PD reduction, and secondary outcomes were clinical attachment level (CAL) change and patient-reported outcome measures (PROMs). Outcome variables were measured at baseline, 3 and 6 months. The examiner was blinded. Statistical analysis, one site for each patient, included descriptive statistics and analysis of covariance. Forty-six participants were enrolled, and one patient dropped out in the PPF group. After 6 months, both treatments resulted in significant PD reduction (1.3 ± 1.2 mm, p = .009 NSR; 2.0 ± 0.7 mm, p < .001 PPF) and CAL gain (1.0 ± 2.4 mm, p = .031 NSR; 1.4 ± 0.8 mm, p < .001 PPF). PD reduction between groups was not statistically significant (diff: 0.6 mm; 95% confidence interval [CI] [-0.3 to 1.5]; p = .167). Pocket closure was 61% NSR versus 86% PPF (p = .091). Smoking was associated with less PD reduction of almost 1 mm in both treatments. Treatment time was longer for PPF surgery, but PROMs and post-operative pain were similar between groups. Both NSR and PPF reduced PD without significant difference between treatments at 6 months. PPF surgery may offer faster PD reduction, but smoking habits reduce treatment efficacy.

Sn-doped PdAg/Al2O3 catalysts: Efficient catalysts for the selective hydrogenation of acetylene to ethylene under industrial conditions

PdAg/Al2O3 catalysts were prepared using a simple and scalable preparation method. A systematic approach established a preparation-performance relationship which revealed that the Pd:Ag ratio and Pd reduction method affects the overall performance for the selective hydrogenation of acetylene to ethylene under industrially relevant tail-end reaction conditions. The addition of Sn improved selectivity with the optimum system achieving 97% selectivity towards ethylene, outperforming two industrial references. Density functional theory (DFT) simulations and electron microscopy analysis revealed that Sn integrates into the Pd lattice and increases the energy barrier for ethylene adsorption. This work demonstrates that Sn can be used to tailor catalyst performance for industrially relevant PdAg/Al2O3 catalysts.

Metal immobilized in a USY zeolite-supported (4-CB)TPPB: A new strategy of enhanced stability for acetylene hydrochlorination

Palladium (Pd)-based catalysts supported by silicaluminate materials are potential as the efficient non-mercury catalyst for acetylene hydrochlorination, which is a necessary industrial reaction for producing vinyl chloride monomer. A new strategy was employed to improve Pd/USY zeolite catalysts taking advantage of 4-carboxybutyl triphenylphosphonium bromide ((4-CB)TPPB) for acetylene hydrochlorination. The most active catalyst (Pd@20(4-CB)TPPB/USY) with the 0.5 wt% Pd loadings and the 20 wt% (4-CB)TPPB additives could achieve a stable acetylene conversion of 99.9 % and the vinyl chloride selectivity of 99.7 % during more than 50 h, outperforming the Pd/USY catalyst. The additive of (4-CB)TPPB was preferential to stabilize the catalytic active Pd species, inhibit the Pd (II) reduction and change the surface acidic properties during the preparation process and reaction, hence restraining the carbon deposition. Density functional theory (DFT) calculations further indicate that (4-CB)TPPB additives could effectively enhance the adsorption energy of catalyst for reactants and the desorption energy of vinyl chloride monomer (VCM) products, thus inhibiting the carbon deposition for improving the catalytic performance of Pd/USY catalysts. These findings provide guidance for designing efficient Pd-based catalysts as well as their utilization for acetylene hydrochlorination.

Surfactant-free synthesis of nanostructured palladium materials under mild conditions and their highly catalytic selective hydrogenation

Nanostructured palladium (Pd) materials are highly efficient noble metal catalysts in various fields, but developing a simple and mild strategy to prepare Pd nanomaterials with high activity and selectivity still remains a big challenge. In this study, uniform-sized Pd popcorn-like nanospheres (PNSs) were successfully synthesized by the slow reduction of Pd(OAc)2 in anhydrous methanol under ambient conditions in the dark without any surfactant, additional reductant and support. The obtained Pd PNSs have rough surface with the average diameter of approximately 140 nm, and are composed of many smaller PNSs with the average size of about 12 nm. Pd PNSs have excellent catalytic performance in the hydrogenation of 4-nitrobenzaldehyde to 4-aminobenzaldehyde under mild conditions. Specifically, using the as-prepared Pd PNSs as catalyst, the 98 % conversion of 4-nitrobenzaldehyde and 98 % selectivity to 4-aminobenzaldehyde can be achieved within 1.5 h at 35°C under atmospheric pressure. After three recycling, the Pd PNSs can still maintain highly catalytic activity and selectivity. The very simple strategy developed here will be a valuable supplement to the methodology for the surfactant-free fabrication of other surface-active metallic nanomaterials for advanced applications.

The Use of Statins as an Adjunctive Periodontal Disease Treatment: Systematic Review and Meta-Analysis.

the purpose of this systematic review was to assess the clinical and radiographic effect of subgingival-administered statins as an adjunct periodontal treatment in patients with periodontitis. Electronic literature searches in Medline/PubMed and the Cochrane Library were conducted to identify all relevant articles. Eligibility was based on inclusion criteria which included Randomized Controlled Trials (RCTs) published after 2010, where the periodontal variables were assessed before and after periodontal treatment in combination with a statin administration. The risk of bias was assessed with the ROBINS-2 tool. The outcome variables were probing depth, clinical attachment level, bleeding on probing, and bone fill in systematically healthy patients, patients with type 2 diabetes, and smokers. Out of 119 potentially eligible articles, 18 randomized controlled trials were included with a total of 1171 participants. The data retrieved from the meta-analysis showed the positive effect that statins have as an adjunctive periodontal disease treatment. When comparing the different types of statins, the PD reduction in the Simvastatin group was significantly higher than the Atorvastatin group at 6 months and at 9 months, while no differences between statins were found for the rest of the outcomes. Over 66% of the articles presented an overall risk of bias with some concerns, making this a limitation of this present RCT. The adjunct administration of statins has proven to have a positive effect on the periodontium by improving both clinical and radiographic parameters by a considerable margin.

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.

Effects of minimally invasive non-surgical therapy on C-reactive protein, lipoprotein-associated phospholipase A2, and clinical outcomes in periodontitis patients: A 1-year randomized, controlled clinical trial.

Growing evidence suggests the type of periodontal treatment could differentially influence the reduction of key cardiovascular risk mediators in periodontitis patients. This randomized, controlled clinical trial compared the impact of minimally invasive non-surgical therapy (MINST) with quadrant-wise subgingival instrumentation (Q-SI) on C-reactive protein (CRP) together with lipoprotein-associated phospholipase A2 (Lp-PLA2) levels, and clinical periodontal outcomes in patients with periodontitis. Moreover, it was evaluated if baseline CRP levels impacted the efficacy of non-surgical periodontal therapy protocols. Forty-two periodontitis patients were enrolled and randomly treated by means of MINST (n=21) or Q-SI (n=21). The outcomes assessed were serum CRP and Lp-PLA2, and periodontal parameters (probing depth [PD], clinical attachment level [CAL], full-mouth bleeding score [FMBS]), at baseline and at follow-ups at 1, 3, and 6 months and at 1 year after treatment. At 1 year, MINST significantly reduced, among others, mean PD (p=0.007), mean CAL (p=0.007), the number of pockets>4mm (p=0.011) and ≥6mm (p=0.005), and FMBS (p=0.048) compared to Q-SI. Generalized multivariate analysis evidenced that high baseline CRP (p=0.039) and FMBS (p=0.046) levels, together with MINST treatment (p=0.007) were significant predictors of PD reduction at 1-year follow-up. Moreover, the Jonckheere-Terpstra test showed that patients with high baseline CRP levels gained more benefits from MINST treatment at 1-year follow-up than they did from Q-SI. Patients receiving MINST showed a greater reduction in CRP levels than patients with Q-SI after 1 year of follow-up. Moreover, patients with high baseline levels of CRP and Lp-PLA2 gained more benefits from the MINST approach at 1-year follow-up.

Highly active polyethylene glycol grafted cellulose supported Pd nanoparticles for glucose electrooxidation

In this study, poly(ethylene glycol) (PEG) grafted cellulose (CE) composite catalyst support material (PEG-CE) was obtained by chemically cross-linking PEG at varying molecular weight and CE with isophorone diisocyanate (IPDI) and 2,4-toluylene diisocyanate (TDI). PEG-CE supported Pd (Pd/PEG-CE) catalyst was prepared by the chemical reduction method. The crystal size of the Pd/PEG-CE catalyst is 4.79 nm and its crystal structure has been determined to be face-centered cubic Pd. Elemental mapping results indicate that Pd was reduced onto PEG-CE successfully and uniformly. Pd exists in the elemental and Pd-O form in the catalyst system. The Pd loading rate of Pd/PEG-C_IPDI catalyst was determined as 18.8% by mass. Among the PEG-CEs prepared with TDI and IPDI, PEG4000-CE_TDI and PEG6000-CE_IPDI displayed the highest specific activities of 1.03 and 1.50 mA cm−2 for glucose electrooxidation. With Pd reduction on PEG4000-CE_TDI and PEG6000-CE_IPDI, the specific activities increased to 1.62 mA cm−2 and 6.97 mA cm‐2. Pd/PEG6000-CE_IPDI has the highest electrocatalytic activity and stability in this study for glucose electrooxidation and is an encouraging anode catalyst for direct glucose fuel cells.

The Pd (II) Reduction Mechanisms in Bacillus megaterium Y-4 Revealed by Proteomic Analysis.

Many studies have been conducted on the microbial reduction of Pd (II) to palladium nanoparticles (Pd-NPs) due to the environmental friendliness, low cost, and the decreased toxicity of Pd (II) ions. In this study, we investigate the reduction mechanism of Pd (II) by Bacillus megaterium Y-4 through proteomics. The data are available via ProteomeXchange with identifier PXD049711. Our results revealed that B. megaterium Y-4 may use the endogenous electron donor (NAD(P)H) generated by nirB, tdh, and fabG and reductase to reduce Pd (II) to Pd-NPs. The expression levels of fabG, tdh, gudB, and rocG that generate NAD(P)H were further increased, and the number of reduced Pd-NPs was further increased with the exogenous electron donor sodium formate. Endogenous electron mediators such as quinones and flavins in B. megaterium Y-4 can further enhance Pd (II) reduction. The findings provided invaluable information regarding the reduction mechanism of Pd (II) by B. megaterium Y-4 at the proteome level.

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 ≈2nm 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.

Palladium (0) nanoparticles distributed on lanthanum (III) oxide as an effective catalyst for the methanolysis of hydrazine-borane to produce hydrogen.

Pd (0) nanoparticles (NPs) distributed on lanthanum (III) oxide were ex situ generated from the reduction of Pd2+ ions using NaBH4 as reducing agent. The Pd/La2O3 displayed good catalytic activity in H2(g) releasing from the hydrazine-borane (HB) methanolysis reaction and it was identified by advanced techniques. Pd/La2O3 was found to be an active catalyst procuring three equiv. H2(g) per mole of HB. The results from TEM images represent the formation of Pd (0) NPs with an average particle size of 1.94 ± 0.1 nm on the surface of La2O3. Moreover, Pd/La2O3 with various Pd loadings were prepared and tested as catalyst in the methanolysis reaction to find the optimum metal loading on La2O3 support. The highest H2 formation rate was achieved with 3.0 wt% Pd. Pd/La2O3 catalyst exhibited a turnover frequency (TOF) value of 24.4 mol H2 mol Pd-1 min-1 in the reaction conditions. Additionally, the effect of different catalyst concentrations and temperatures on the reaction kinetics for the methanolysis of HB catalyzed by Pd/La2O3.