Reaction Of Pt Research Articles

Synthetic Approaches to and Structures of Diplatinum Polyynediyl Complexes trans,trans‐[(C6F5)(R3P)2Pt(C≡C)nPt(PR3)2(C6F5)] With Odd Numbers of Triple Bonds; Avoiding Complicating Ethynediyl Extrusions

AbstractReactions of trans‐(C6F5)(p‐tol3P)2Pt(C≡C)nSiEt3 (PtC2nSi; n=5, 7, 9) and excess PtCl in the presence of wet n‐Bu4N+ F− (to effect protodesilylation) under Sonogashira‐type conditions (CuCl, base, other additives) afford the title compounds PtC10Pt, PtC14Pt, and PtC18Pt in 42–32 % yields. A four‐fold substitution of the phosphine ligands in PtC10Pt by PEt3 affords Pt'C10Pt’ (78 %), and a Sonogashira reaction of Pt'C2H and Pt'Cl affords Pt'C2Pt’ (68 %). The analogous reaction with PtC2Si and PtCl is unsuccessful, presumably for steric reasons. The crystal structures of PtC10Pt, PtC14Pt, Pt'C10Pt′, and Pt'C2Pt’ exhibit a number of interesting trends and features. Certain sp chain extension reactions that lead to or employ the precursors PtC10Si, PtC12Si, PtC14Si, and PtC18Si sometimes give byproducts derived from C2 loss, and possible origins are discussed. Related phenomena have been reported by others in the course of synthesizing extended conjugated polyynes.

Enhancing acetone detection of In2O3-decorated MOF-derived Fe2O3 spindles with Pt nanoparticles functionalization

Designsensing materials with core-shell structure is an excellent strategy to achieve high sensing performance toward acetone detection. Herein, MIL-88A(Fe) was fabricated via a hydrothermal route, which renders as a template to fabricate Fe2O3@In2O3 core-shell spindles structure. Gas sensing results show that the sensor based on Fe2O3@In2O3 exhibit enhanced response of 193–200 ppm acetone than that of 36 for pristine Fe2O3 at 200 °C. After Pt functionalization, the response of Fe2O3@In2O3/Pt to 200 ppm acetone is up to 839 at a reducing working temperature of 180 °C with a good selectivity and long-term stability. A synergistic mechanism originated from the intrinsic merits of Fe2O3 and In2O3, the 1D core-shell structure, the creation of heterojunction at the interface of Fe2O3 and In2O3 and the creation of Shottky junction at In2O3 and Pt nanoparticles, and the catalytic reaction of Pt holds accountable for the significant improvement in acetone sensing.

Regioselective ligand substitution in square-planar Pt(II) complexes bearing N^C and C^C chelating ligands with pyrazole derivatives

The regioselectivity of the ligand substitution reaction of square-planar Pt(II) complexes with chelating ligands pyridyl-NHC (Py-NHC), phenyl-NHC (Ph-NHC), and phenyl-pyridine (ppy, Ph-Py) was studied. The reaction of the dichlorido Pt(II) complex bearing these chelating ligands in the presence of pyrazole (pz) ligands afforded mono-pyrazole adducts [PtCl(ChL)(pz)]n+ (n = 0 and 1; ChL=chelating ligand (Py-NHC, Ph-NHC, Ph-py)). The structures of the PtCl(pz) complexes with the Py-NHC, Ph-NHC, and Ph-Py chelating ligands were confirmed by X-ray crystallographic analysis. The regioselectivity of the ligand substitution reaction between the pyrazole moieties and chloride ions can be controlled by the strength of the trans effect of the chelating ligands. Based on the structures of the products, a clear trend of Py < NHC < Ph was observed in the trans effect of the chelating ligands. This finding provides a rational synthetic procedure for asymmetric Pt(II) complexes with chelating ligands in a stepwise manner.

Theoretical study of electrochemical hydrogen evolution reaction of Pt–Co diatomic sites catalyst

Hydrolytic Hydrogen is a clean hydrogen production method. To mitigate the substantial costs associated with water electrolysis, electrocatalysts are crucial in decreasing the cathodic reaction involved in hydrogen hydrolysis, specifically, the overpotential for hydrogen evolution reaction (HER). Compared to traditional catalysts and single-atom catalysts, Pt–Co diatomic sites catalyst exhibit excellent hydrogen evolution reaction activity and stability. We have established eight different structures of dual-center metal catalysts based on graphene planes. A systematic study was conducted on the catalytic performance and mechanism of these configurations, among which the structure with the best hydrogen evolution reaction activity was CoN4/PtC2N2, with a Gibbs free energy (ΔG) of 0.004 eV. Electronic structure analysis confirms that H follows the Sabatier mechanism on diatomic catalysts, and the catalyst exhibits excellent HER performance for moderate adsorption strength of H atoms. The d-band centers of Co and Pt atoms in the electrocatalyst CoN4–PtC2N2 are lower than those of a single system, indicating that the electronic effect between the CoN4 and PtC2N2 sites can enhance the inherent HER activity of the catalyst. This study expands the application scope of dual-site catalysts and provides new insights for the design and synthesis of dual-site hydrogen evolution catalysts.

An expanded hydrogen-bonded organic framework formed by a tetrakis(terphenyl)ethene derivative

Abstract A low-density hydrogen-bonded organic framework (HOF) with channel aperture with dimensions of 33.8 Å × 55.2 Å was constructed from a tetrakis(terphenyl)ethene derivative. The structure was successfully characterized by single crystalline X-ray diffraction analysis. Although solvent molecules are included in the channel, the present framework is one of the HOFs with the largest aperture. The framework is based on H-bonded sql-networks that stack in an eclipse fashion. The interlayer interactions were thoroughly investigated on the basis of the crystal structure. Interestingly, thee analogues of tetraarylethene-based tetracarboxylic acids, including the title compounds, formed the same H-bonded sql-network as a lower-dimensional supramolecular motif. However, the motifs are assembled in completely different ways to give the corresponding three types of the framework, indicating the importance of precise design of the secondary interactions between the lower dimensional motifs. In solid state, the molecular unit of the constructed HOF shows a largely Stokes-shifted and strong emission due to a fast (&amp;lt; 15 ps) ICT and a relatively slower (90 ps) intermolecular PT reaction, while in DMF it exhibits a strong H-bond with the solvent.

Quantitative DEMS analysis of CO2 evolution reactions in alkaline electrolyte solutions

CO2 evolution is involved in various main and side reactions of electrochemical systems, such as carbon corrosion reactions and alcohol oxidation reactions. Differential electrochemical mass spectroscopy (DEMS) has been intensively applied to analyze the partial current of the CO2 evolution reaction in acidic and neutral electrolyte solutions. However, the quantitative analysis of the CO2 evolution reaction in alkaline electrolyte solutions has not been successful when catalyst-loaded carbon electrodes were applied, due to the high solubility of CO2 in the electrolyte. In this study, we develop a new DEMS system combining microreactor and ion exchange membrane to quantitatively analyze CO2 evolution reactions of catalyst-loaded carbon electrodes in alkaline electrolyte solutions. The calibration constant, which correlates the mass signal of m/z = 44 to the partial current of the CO2 evolution reaction, is successfully obtained from the Faradaic current and the mass signal of CO stripping voltammetry. We analyze carbon corrosion reactions of Pt and metal oxide-loaded carbon electrodes to demonstrate the effectiveness of the constructed system. The corrosion behavior of the Pt-loaded carbon is similar to that in the acidic electrolytes except for the onset potential of the carbon corrosion. La0.6Ca0.4CoO3 and Ca2FeCoO5 show electrochemical carbon corrosion activity, while La0.4Sr0.6MnO3 does not show distinct electrochemical carbon corrosion activity.

A randomised, double-blinded trial to assess the effect of oclacitinib and prednisolone on intradermal allergen and prick tests in dogs with atopic dermatitis.

Intradermal (IDT) and prick (PT) tests are used to select allergens for allergen-specific immunotherapy in dogs with atopic dermatitis (cAD). However, the use of antipruritic drugs before performing these tests may influence the results. To evaluate the influence of the drugs oclacitinib and prednisolone on the immediate-phase reactions of IDT and PT. Thirty client-owned dogs with cAD with positive reactions to at least one allergen extract on IDT or PT. Dogs were randomly assigned to receive oclacitinib 0.4-0.58 mg/kg per os, every 12 h (n = 14), or prednisolone 0.37-0.65 mg/kg p.o., every 12 h (n = 16) for 14 days. IDT and PT were performed on Day (D)0 before treatment and on D14. At D14 there was no significant reduction in the means of the orthogonal diameters of the positive immediate-phase reactions of the IDT (p = 0.064) in the oclacitinib group; however, in the PT, the diameter of the positive reactions reduced significantly (p = 0.048). In both tests, there was no significant reduction in the total number of positive reactions (IDT, p > 0.999; PT, p = 0.735). In the prednisolone group, the means of the orthogonal diameters of positive immediate-phase reactions were significantly reduced in both tests (IDT, p = 0.001; PT, p ≤ 0.001) and there also was a reduction in the total number of positive reactions (IDT, p = 0.022; PT, p = 0.001). The use of oclacitinib 0.4-0.58 mg/kg twice daily for 14 days does not interfere with IDT results in dogs with cAD. However, oclacitinib may reduce PT reactivity. The use of prednisolone 0.37-0.65 mg/kg twice daily results in a reduction in both IDT and PT results.

Ternary PtZrNi nanorods for efficient multifunctional electrocatalysis towards oxygen reduction and alcohol oxidation

Pt-based alloys with precise structure and composition design have been considered to be effective and robust novel electrocatalysts for fuel cells. Whereas, the sluggish kinetics of oxygen reduction reaction (ORR) and low intrinsic activity of Pt limited their real application on a large scale. Herein, a novel ternary PtZrNi nanorods (PtZrNi NRs) was synthesized via a facile wet-chemical method to achieve high electrocatalytic performance for both ORR and alcohol oxidation reaction owing to the synergism of chosen three elements and prominent one-dimensional morphology. Specifically, the PtZrNi NRs show enhanced mass and specific activities of 0.755 A mgPt-1 and of 0.97 mA/cm2 at 0.9 VRHE towards ORR in acidic media, which are 4.7 and 4.4 times of those of commercial Pt/C, respectively. Additionally, in alkaline media, the PtZrNi NRs also exhibit superior ORR mass and specific activities of 3.216 A mgPt-1and 4.13 mA/cm2, enhanced by 34.6 and 31.3 times compared with those of commercial Pt/C, respectively. The PtZrNi NRs retain the nanorod shape well without agglomeration after an accelerated durability test (20000 cycles). This work may offer a new perspective for engineering high-performance Pt-based electrocatalysts for commercial fuel cells.

Pt phosphor-, oxygen-rich complexes: One pot synthesis, characterization, molecular docking and antiproliferative study

This work includes the synthesis of a series of O- and P- rich platinum complexes by the reaction of Pt+2 with tertiary phosphines (PPh3, dppm, dppe, dppp, dppf) and 3,4,5‑trimethoxybenzoic acid (HTMB) through a one-pot reaction. All complexes were characterized using FTIR, CHN, molar conductivity, 1H NMR and 31P NMR. The characterization results proved that the TMB ligand in all complexes behaves as a monodentate through the deprotonated oxygen atom. The phosphine ligands were associated to platinum center with chelating bidentate mode while PPh3 and dppm were behaved as monodentate and bridging bidentate ligands, respectively. The PPh3-containing complex (trans-[Pt(TMB)2(PPh3)2]) was used to examine its anticancer activity against A2780, SW620, HT29, A172, C6 and HeLa cell lines. The results proved that the TGI value was 40.33 ± 1.4, 18.05 ± 0.8, 48.91 ± 1.6, 44.43 ± 2.8, 51.03 ± 2.0 and 56.98 ± 2.1 for A172, C6, HeLa, A2780, SW620 and HT29, respectively. TGI values were better than those reported for the reference compound 5FU. The molecular docking proves that trans-[Pt(TMB)2(PPh3)2] have pi-alkyl hydrophobic interaction, carbon-hydrogen bonding, electrostatic interaction and pi-lone pair interaction with different amino acids.

Synthesis of Pt(ii) phosphinocarboxylate complexes with auxiliary arylcarbene ligands and factors that control their stereochemistry

Reactions of Pt(ii)-acetylacetonate complexes with orthoplatinated carbene ligands and a ferrocene phosphinocarboxylic acid produce phosphinocarboxylate complexes as single isomers. The factors that control the stereochemistry were investigated.

Enhancing oxygen reduction reaction of Pt–Co/C nanocatalysts via synergetic effect between Pt and Co prepared by one-pot synthesis

Enhancing oxygen reduction reaction of Pt–Co/C nanocatalysts via synergetic effect between Pt and Co prepared by one-pot synthesis

Oxygen Reduction Reaction of Pt and Non-PGM Transition Metal High Entropy Alloys Single Crystal Stacking Structures

Introduction Nanoparticles of Pt as well as Pt-based alloys are widely used as cathode catalyst materials for proton exchange membrane fuel cells (PEMFC). However, electrochemical stability of the materials is rather low under practical operating conditions of PEMFC cathode, resulting in severe deactivation of oxygen reduction reaction (ORR). Therefore, further material’s developments are required for next-generation PEMFC cathode catalysts, i.e., more enhanced ORR durability with low platinum group metal (PGM) usage.High entropy alloys (HEAs), defined as single phase solid solutions of five or more elements in equal composition ratios, are known as thermodynamically stable, in comparison to conventional binary alloys. Furthermore, complex atomic-level local structures bring about unique electronic as well as (electro-)chemical properties that originating from lattice strains induced by specific local structures and/or so-called sluggish diffusion of the constituent elements. [1] However, to our best knowledge, no study has been made for ORR properties of Pt alloying with non-PGM Cantor alloy (fcc structure HEA with equi-atomic ratio of Cr-Mn-Fe-Co-Ni [2]) elements in strong acid condition.In this study, we synthesized lattice stacking structures of Pt/HEA(hkl) (hkl = (111), (110), (100)) through arc-plasma deposition (APD) of the Cantor alloy layer on Pt(hkl) substrate surfaces, followed by deposition of the surface Pt layer in ~10-7 Pa. Then, we performed cross-sectional STEM-EDS observations for Pt/HEA/Pt(hkl) stacking structures with atomic-level resolution and evaluated the ORR properties (initial activity and structural stability). Experimental An APD target of Cr-Mn-Fe-Co-Ni (Cantor alloy) was fabricated by sintering of equal quantity corresponding elements. 10 ML(monolayer)-thick (1 ML = ca. 0.3 nm) Cantor alloy layer (as HEA) was vacuum-deposited by APD on surface cleaned Pt(hkl) substrate surfaces at 300 K, and subsequently annealed in vacuum at 773 K for 30 minutes. Then, 4ML-thick Pt layer was deposited on the pre-deposited Cantor alloy layer at 300 K and annealed at 623 K. The samples thus prepared are designated as Pt/HEA/Pt(hkl). The atomic-level micro-structures and chemical bonding states of Pt/HEA/Pt(hkl) surfaces were characterized by cross-sectional STEM-EDS, RHEED, XPS etc. CV and LSV with the RDE method were conducted in N2-purged and O2-saturated 0.1 M HClO4. ORR activity was evaluated from j k values at 0.9 V vs. RHE by using Koutecky-Levich equation and structural stability (ORR durability) was discussed based upon activity transitions during applying the potential cycles (PCs) of 0.6(3s)‐1.0(3s) V vs. RHE in O2 saturated 0.1 M HClO4 at room temperature. Results and Discussion Atomically-resolved, cross-sectional HAADF-STEM images for Pt/HEA/Pt(hkl) (a) and EDS line profiles of elemental distributions at corresponding yellow arrows (b) are presented in Figure 1. As clearly shown in (a), irrespective of the Pt surface indices, (hkl), HEA (Cantor alloy) and surface Pt layers are epitaxially grown on the substrates. By contrast, elemental distributions in each surface normal (b) seriously depend on the substrate Pt lattice indices. Notably, severe thermal diffusion of the constituent elements including Pt is confirmed by (a) and (b) for both Pt/HEA/Pt(110) and (100). Figure 2 summarizes electrochemical results. 4ML-thick-Pt/10ML-thick-Co/Pt(hkl) that prepared under the same preparation condition of Pt/HEA/Pt(hkl), and clean Pt(hkl) (light blue and gray, respectively) are also shown as references. As shown in the figure, the Pt/HEA and Pt/Co fabricated on Pt(111) substrate (top) show quite similar CV characteristics (shrink in hydrogen adsorption charges (0 – 0.3 V) and higher potential shifts in oxygen-related species adsorption (0.6 – 1.0 V)), in comparison to clean Pt(111), and almost the same initial ORR activity. Meanwhile, the Pt/HEA fabricated on Pt(110) and (100) substrates show more reduced hydrogen absorption charges, compared with corresponding Pt/Co samples. Particularly, distinctive redox features for clean Pt(110) at 0.12 V and for Pt(100) at 0.35 V are absent for corresponding CVs, suggesting specific topmost surface atomic-structures might be formed in the electrolyte, that probably resulting from significant electronic interactions between surface Pt and HEA constituent elements (Cr, Mn, Fe, Co, Ni) and/or local strain of the surface Pt layer induced by distorted Pt-HEA lattices located nearby. One might notice that Pt/HEA/Pt(110) reveals remarkable ORR activity enhancement compared with corresponding Pt/Co/Pt(110), while the activities for Pt/HEA and corresponding Pt/Co surfaces fabricated on Pt(100) are almost the same value. At the meeting, correlations between surface atomic-level micro-structures of Pt/HEA/Pt(hkl) and ORR properties will be discussed in detail. Acknowledgement This study was supported by new energy and industrial technology development organization (NEDO) of Japan and JST SPRING, Grant Number JPMJJSP2114.Reference[1] J. Yeh, JOM, 65, 1759 (2013).[2] B. Cantor et al., Mater. Sci. Eng. A, 375, 213 (2004). Figure 1

Phosphate-decorated Pt Nanoparticles as Methanol-tolerant Oxygen Reduction Electrocatalyst for Direct Methanol Fuel Cells

In a direct methanol fuel cell system (DMFC), one of the drawbacks is methanol crossover. Methanol from the anode passes through the membrane and enters the cathode, causing mixed potential in the cell. Only Pt-based catalysts are capable of operating as cathode for oxygen reduction reaction (ORR) in a harsh acidic condition of DMFC. However, it causes mixed potential due to high activity toward methanol oxidation reaction of Pt. To overcome this situation, developing Pt-based catalyst that has methanol tolerance is significant, by controlling reactant adsorption or reaction kinetics. Pt/C decorated with phosphate ion was prepared by modified polyol method as cathode catalyst in DMFC. Phosphate ions, bonded to the carbon of Pt/C, surround free Pt surface and block only methanol adsorption on Pt, not oxygen. It leads to the suppression of methanol oxidation in an oxygen atmosphere, resulting in high DMFC performance compared to pristine Pt/C.

Tunable fluorescence of Imidazo[1,2‐a]pyridine derivatives with additional proton transfer sites Harnessing excited-state intramolecular double proton transfer: Theoretical insight

Electronic properties and excited-state intramolecular proton transfers of a new designed series of doubly intramolecular hydrogen bonding molecules having imidazo[1,2-a]pyridines as proton acceptors with different types of proton donors (hydroxy-type, amino-type, and mixing-type) and their derivatives have been theoretically evaluated for fluorescent probes. Overall, all designed molecules are photoexcited at ∼420 nm and give fluorescence in the NIR region with large Stokes shifts. The fluorescence of NH- and Mixed-type molecules are notably longer than that of OH-type molecules, and those of the derivatives with a π-conjugated spacer are slightly longer than those of their analogues. Based on the kinetic and thermodynamic information, all designed molecules could not exhibit the double proton transfer (DPT) process but only single proton transfer (SPT) is preferred. Moreover, the dynamic simulations on the excited-state confirm that only SPT is allowed but not DPT in accordance with the predicted PT barriers and reaction energies, leading only NT* fluorescence but their NT* fluorescence maxima are still in the NIR region (600–900 nm) with large Stokes shifts (∼300 nm). The NIR fluorescence is caused by an additional PT unit and a π-conjugated spacer induce the ICT character evidenced by the EDD maps. Therefore, these designed molecules exhibiting NIR tautomer emission with large Stokes shifts could be potential candidates for NIR fluorescent probes with avoiding self-absorption and less photo-damage.

Thermochemistry and mechanisms of the Pt+ + SO2 reaction from guided ion beam tandem mass spectrometry and theory.

The kinetic energy dependences of the reactions of Pt+ (2D5/2) with SO2 were studied using a guided ion beam tandem mass spectrometer and theory. The observed cationic products are PtO+ and PtSO+, with small amounts of PtS+, all formed in endothermic reactions. Modeling the kinetic energy dependent product cross sections allows determination of the product bond dissociation energies (BDEs): D0(Pt+-O) = 3.14 ± 0.11eV, D0(Pt+-S) = 3.68 ± 0.31eV, and D0(Pt+-SO) = 3.03 ± 0.12eV. The oxide BDE agrees well with more precise literature values, whereas the latter two results are the first such measurements. Quantum mechanical calculations were performed for PtO+, PtS+, PtO2 +, and PtSO+ at the B3LYP and coupled-cluster with single, double, and perturbative triple [CCSD(T)] levels of theory using the def2-XZVPPD (X = T, Q) and aug-cc-pVXZ (X = T, Q, 5) basis sets and complete basis set extrapolations. These theoretical BDEs agree well with the experimental values. After including empirical spin-orbit corrections, the product ground states are determined as PtO+ (4Σ3/2), PtS+ (4Σ3/2), PtO2 + (2Σg +), and PtSO+ (2A'). Potential energy profiles including intermediates and transition states for each reaction were also calculated at the B3LYP/def2-TZVPPD level. Periodic trends in the thermochemistry of the group 9 metal chalcogenide cations are compared, and the formation of PtO+ from the Pt+ + SO2 reaction is compared with those from the Pt+ + O2, CO2, CO, and NO reactions.

Anomalous photo-thermoelectric effects of platinum-photodeposited tungsten trioxide after gaschromic reaction

We attempted to deposit platinum (Pt) onto a tungsten trioxide (WO3) thin film by the photoreduction of Pt4+ (Pt–WO3). Pt on WO3 was oxidized (PtOx) by calcining Pt–WO3 in air to form PtOx–WO3. An n-type anomalous photo-thermoelectric (photo-TE) effect was confirmed for Pt–HyWO3−x, a protonated WO3, after the gaschromic (GC) reaction of Pt–WO3. That is, both the electrical conductivity (σphoto) and the absolute value of the Seebeck coefficient (Sphoto) increased under visible-light irradiation. After stopping the irradiation, both values decreased (σ and S). In contrast, an n-type normal photo-TE effect was observed for PtOx–HyWO3−x after the GC reaction of PtOx–WO3, in which σphoto and the absolute value of Sphoto increased and decreased, respectively, under visible-light irradiation, and vice versa after stopping the irradiation. These findings indicate that Pt was responsible for the generation of the anomalous photo-TE effect, probably due to the electron accumulation capability of Pt, to which electrons were transferred from the conduction band of HyWO3−x. In contrast, electrons could not energetically transfer from HyWO3−x to PtO2, which was included in PtOx particles at the surface. Therefore, PtOx was not responsible for the anomalous photo-TE effect, and PtOx–HyWO3−x behaved like bare HyWO3−x, indicating its normal photo-TE effect.

Self-assembled Pt–CoFe layered double hydroxides for efficient alkaline water/seawater splitting by spontaneous redox synthesis

The development of high-performance, low-cost and large-scale water/seawater splitting bifunctional electrocatalysts still faces huge challenges. Here, we deliver a novel and simple spontaneous redox synthesis strategy to fabricate a self-supported Pt–CoFe(Ⅱ) layered double hydroxide (LDH) electrocatalyst. The three-dimensional porous structure of the catalyst and the synergistic effect of Pt clusters and CoFe hydroxides jointly contribute to its excellent catalytic activity and enhanced chemical stability. Specifically, in 1 M KOH, the overpotentials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of Pt–CoFe(Ⅱ) LDH at 10 mA cm−2 are 214 mV and 15 mV, respectively. The catalysts are stable for at least 40 h at high current densities of 100 and 500 mA cm−2. Compared with previously reported electrocatalysts, Pt–CoFe(II) LDHs || Pt–CoFe(II) LDHs overall water (seawater) electrolyzers only require 1.634 (1.651) and 1.798 (1.858) V to reach 100 and 500 mA cm−2 in 1 M KOH water (seawater) electrolyte, confirming the superior catalytic activity of the self-supported Pt–CoFe(Ⅱ) layered double hydroxide electrocatalysts. This study provides a novel and simple synthesis strategy to prepare advanced water/seawater splitting electrocatalysts, which is highly relevant for commercial applications.

Star-shaped Pd(II) and Pt(II) complexes containing C3-symmetric conjugated thiophenes: Synthesis, characterization, and chemical reactions with organic unsaturated molecules

Triple oxidative addition reactions of [M0(styrene)(PMe3)2] (M = Pd/Pt) with C3-symmetric star-shaped molecules containing 1-, 3-, and 5-thiophene-substituted benzene, in 1:0.3 ratio, afforded new Pd(II) and Pt(II) trinuclear complexes in suitable yields. Analogous trinuclear complexes were formed by similar reactions of thiophenyl halide derivatives containing triazine or triphenylamine cores. Alternatively, a trinuclear Pd(II) complex was obtained by oxidative addition of a Pd(0) complex (synthesized from allyl(cyclopentadienyl) palladium(II), [(η5-C5H5)Pd(η3-C3H5)] with PEt3. Sonogashira-type coupling between trinuclear Pt(II) halides (containing C3-symmetric conjugated thiophenes) and alkynes, in the presence of cuprous halide and diethylamine, afforded alkynyl-containing trinuclear Pt(II) complexes with extended π-conjugation. Insertion reactions of organic isocyanides (CN-R) with trinuclear Pd(II) complexes yielded trinuclear Pd(II) imidoyl complexes by insertion of CN-R into Pd-carbon (thiophene) bonds. Reactions of trinuclear Pt(II) halides with Ag(OCOCF3) and NaN3 formed pseudohalogen-containing Pt(II) complexes.

Surface-Limited Galvanic Replacement Reactions of Pd, Pt, and Au onto Ag Core Nanoparticles through Redox Potential Tuning

Surface-Limited Galvanic Replacement Reactions of Pd, Pt, and Au onto Ag Core Nanoparticles through Redox Potential Tuning

New Insights of the pH Effect on Hydrogen Evolution and Oxidation Reactions Mechanisms in Alkaline Solutions

The sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) of Pt in alkaline solutions remains elusive. Elucidation of the mechanisms of the HER/HOR in alkaline can not only deepen our understandings of alkaline electrochemistry, but also help to rationalize the design of highly active catalysts for alkaline fuel cells and electrolyzers. Herein, we investigate the HER/HOR kinetics of a variety of catalysts including monometallic catalysts (Ni, Pt, Ru, Au) and bimetallic catalysts (NiMo, Pt-M) by comparing their HER/HOR performance in 0.1 M KOH and 1 M KOH. We found that the HER/HOR kinetics of these systems are not always slower in 1 M KOH (pH =14) than in 0.1 M KOH (pH = 13). These observations do not follow the general trend that the HER/HOR kinetics of a wide range of elements slows down with increasing pH1. We propose to resolve this inconsistency by pointing out that the pH is only one of the factors that affect the transport of the HER/HOR intermediates (hydroxyl for HER, Had for HOR) throughout the double layer region, among other factors such as the oxophicility of the surface sites, the cation environment, etc. These factors co-determine the HER/HOR kinetics of catalysts (such as Pt/C) that is limited by the transport of reactions throughout the double layer region. As the electrolyte changes from 0.1 M KOH to 1 M KOH, the pH shifts from 13 to 14, slowing down the HER/HOR kinetics. Meanwhile, the K+ concentration increases one order of magnitude, which promotes the transport of OHad according to the hard-soft acid-base (HSAB) mechanism we recently proposed 2, thereby improving the HER but not the HOR until the K+ saturates. The change of the HER/HOR kinetics of a catalyst as the electrolyte changes from 0.1 M KOH to 1 M KOH is a counterbalance between these two effects, and thus varies case by case. Acknowledgements.This work was supported by the Department of Energy (DOE) under award number DE-EE0008082, Office of Naval Research (ONR) under award number N000141712608 and the Graduate Thesis/Dissertation Grant of Northeastern University. This research used beamline 7-BM (QAS) and 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. References (1)Herranz, J.; Durst, J.; Fabbri, E.; Patru, A.; Cheng, X.; Permyakova, A. A.; Schmidt, T. J. Interfacial Effects on the Catalysis of the Hydrogen Evolution, Oxygen Evolution and CO2-Reduction Reactions for (Co-)Electrolyzer Development. Nano Energy 2016, 29, 4–28. https://doi.org/10.1016/j.nanoen.2016.01.027.(2)Liu, E.; Li, J.; Jiao, L.; Doan, H. T. T.; Liu, Z.; Zhao, Z.; Huang, Y.; Abraham, K. M.; Mukerjee, S.; Jia, Q. Unifying the Hydrogen Evolution and Oxidation Reactions Kinetics in Base by Identifying the Catalytic Roles of Hydroxyl-Water-Cation Adducts. J. Am. Chem. Soc. 2019, 141 (7), 3232–3239. https://doi.org/10.1021/jacs.8b13228.