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Keywords = PtPd alloy catalyst

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14 pages, 1940 KiB  
Article
Nanoporous CuAuPtPd Quasi-High-Entropy Alloy Prism Arrays for Sustainable Electrochemical Nitrogen Reduction
by Shuping Hou, Ziying Meng, Weimin Zhao and Zhifeng Wang
Metals 2025, 15(5), 568; https://doi.org/10.3390/met15050568 - 21 May 2025
Viewed by 465
Abstract
Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, [...] Read more.
Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, known for their exceptional chemical stability under electrocatalytic conditions, have garnered considerable attention in this field. In this study, we report the successful synthesis of nanoporous CuAuPtPd quasi-high-entropy alloy (quasi-HEA) prism arrays through “melt quenching” and “dealloying” techniques. The as-obtained alloy demonstrates remarkable performance as an NRR electrocatalyst, achieving an impressive ammonia synthesis rate of 17.5 μg h−1 mg−1 at a potential of −0.2 V vs. RHE, surpassing many previously reported NRR catalysts. This work not only highlights the potential of quasi-HEAs as advanced NRR electrocatalysts but also provides valuable insights into the design of nanoporous multicomponent materials for sustainable energy and catalytic applications. Full article
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13 pages, 1568 KiB  
Article
Methanol-Tolerant Pd-Co Alloy Nanoparticles on Reduced Graphene Oxide as Cathode Catalyst for Oxygen Reduction in Fuel Cells
by Chandra Sekhar Yellatur, Venkatachalam Vinothkumar, Poshan Kumar Reddy Kuppam, Juwon Oh and Tae Hyun Kim
Catalysts 2025, 15(2), 128; https://doi.org/10.3390/catal15020128 - 29 Jan 2025
Viewed by 1198
Abstract
The design of efficient and cost-effective electrocatalysts to replace Pt in an oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cell (PEMFC) technologies. This study synthesized Pd-Co bimetallic alloy nanoparticles supported on reduced graphene oxide (rGO) through a simple [...] Read more.
The design of efficient and cost-effective electrocatalysts to replace Pt in an oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cell (PEMFC) technologies. This study synthesized Pd-Co bimetallic alloy nanoparticles supported on reduced graphene oxide (rGO) through a simple chemical-reduction method, making it suitable for low-cost, large-scale fabrication and significantly reducing the need for Pt. The nanostructures were systematically characterized using various analytical techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Electrochemical investigations revealed that the Pd-Co/rGO catalyst exhibits remarkable ORR performance in an alkaline environment, with an electrode-area-normalized activity rivaling that of the commercial Pt/C catalyst. Remarkably, Pd-Co/rGO demonstrated an onset potential (Eonset) of 0.944 V (vs. RHE) and a half-wave potential (E1/2) of 0.782 V (vs. RHE), highlighting its excellent ORR activity. Furthermore, the Pd-Co/rGO catalyst displayed superior methanol-tolerant ORR activity, outperforming Pt/C and monometallic Pd/rGO and Co/rGO systems. The enhanced electrocatalytic performance is attributed to the smallest size, consistent shape, and good dispersion of the alloy structure on the RGO surface. These findings establish Pd-Co/rGO as a promising alternative to Pt-based catalysts, addressing key challenges such as methanol crossover while advancing PEMFC technology in alkaline media. Full article
(This article belongs to the Special Issue Insight into Electrocatalysts for Oxygen Reduction Reaction)
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16 pages, 4793 KiB  
Article
Simulation of Surface Segregation in Nanoparticles of Pt-Pd Alloys
by Jose Brito Correia and Ana Isabel de Sá
Crystals 2025, 15(1), 53; https://doi.org/10.3390/cryst15010053 - 7 Jan 2025
Cited by 5 | Viewed by 1101
Abstract
Platinum (Pt) and palladium (Pd) are crucial in hydrogen energy technologies, especially in fuel cells, due to their high catalytic activity and chemical stability. Pt-Pd nanoparticles, produced through various methods, enhance catalytic performance based on their size, shape, and composition. These nanocatalysts excel [...] Read more.
Platinum (Pt) and palladium (Pd) are crucial in hydrogen energy technologies, especially in fuel cells, due to their high catalytic activity and chemical stability. Pt-Pd nanoparticles, produced through various methods, enhance catalytic performance based on their size, shape, and composition. These nanocatalysts excel in direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs) by promoting alcohol oxidation and reducing CO poisoning. Pt-Pd catalysts are also being explored for their oxygen reduction reaction (ORR) on the cathodic side of fuel cells, showing higher activity and stability than pure platinum. Molecular dynamics (MD) simulations have been conducted to understand the structural and surface energy effects of PdPt nanoparticles, revealing phase separation and chemical ordering, which are critical for optimizing these catalysts. Pd migration to the surface layer in Pt-Pd alloys minimizes the overall potential energy through the formation of Pd surface monolayers and Pt-Pd bonds, leading to a lower surface energy for intermediate compositions compared to that of the pure elements. The potential energy, calculated from MD simulations, increases with a decreasing particle size due to surface creation, indicating higher reactivity for smaller particles. A general contraction of the average distance to the nearest neighbour atoms was determined for the top surface layers within the nanoparticles. This research highlights the significant impact of Pd segregation on the structural and surface energy properties of Pt-Pd nanoparticles. The formation of Pd monolayers and the resulting core–shell structures influence the catalytic activity and stability of these nanoparticles, with smaller particles exhibiting higher surface energy and reactivity. These findings provide insights into the design and optimization of Pt-Pd nanocatalysts for various applications. Full article
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13 pages, 3069 KiB  
Article
Sub-10 nm PdNi@PtNi Core–Shell Nanoalloys for Efficient Ethanol Electro-Oxidation
by Qian Su and Lei Yu
Molecules 2024, 29(20), 4853; https://doi.org/10.3390/molecules29204853 - 13 Oct 2024
Cited by 4 | Viewed by 1494
Abstract
By controlling the structure and composition of Pt-based nanoalloys, the ethanol oxidation reaction (EOR) performances of Pt alloy catalysts can be effectively improved. Herein, we successfully synthesis sub-10 nm PdNi@PtNi nanoparticles (PdNi@PtNi NPs) with a core–shell structure by a one-pot method. The sub [...] Read more.
By controlling the structure and composition of Pt-based nanoalloys, the ethanol oxidation reaction (EOR) performances of Pt alloy catalysts can be effectively improved. Herein, we successfully synthesis sub-10 nm PdNi@PtNi nanoparticles (PdNi@PtNi NPs) with a core–shell structure by a one-pot method. The sub 10 nm core–shell nanoparticles possess more effective atoms and exhibit a synergistic effect which can lead to a shift in the d-band center and alter binding energies toward adsorbates. Due to the synergistic effect and unique core–shell structure, the PdNi@PtNi NP catalysts exhibit excellent electrocatalytic performance for ethanol oxidation reactions in alkaline, achieving 9.30 times more mass activity and 7.05 times more specific activity that of the state-of-the-art Pt/C catalysts. Moreover, the stability of PdNi@PtNi NPs was also greatly improved over PtNi nanoparticles, PtPd nanoparticles, and commercial Pt/C. This strategy provides a new idea for improving the electrocatalytic performance of Pt-based catalysts for EORs. Full article
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12 pages, 5673 KiB  
Article
Deposition of Pd, Pt, and PdPt Nanoparticles on TiO2 Powder Using Supercritical Fluid Reactive Deposition: Application in the Direct Synthesis of H2O2
by Marlene Crone, Laura L. Trinkies, Roland Dittmeyer and Michael Türk
Molecules 2024, 29(9), 2142; https://doi.org/10.3390/molecules29092142 - 5 May 2024
Cited by 1 | Viewed by 1602
Abstract
In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 [...] Read more.
In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation. Full article
(This article belongs to the Special Issue Processing of Materials by Supercritical Fluids—Part II)
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27 pages, 8072 KiB  
Article
Enhanced Mass Activity and Durability of Bimetallic Pt-Pd Nanoparticles on Sulfated-Zirconia-Doped Graphene Nanoplates for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cell Applications
by Maryam Yaldagard and Michael Arkas
Molecules 2024, 29(9), 2129; https://doi.org/10.3390/molecules29092129 - 3 May 2024
Cited by 5 | Viewed by 2028
Abstract
Developing highly active and durable Pt-based electrocatalysts is crucial for polymer electrolyte membrane fuel cells. This study focuses on the performance of oxygen reduction reaction (ORR) electrocatalysts composed of Pt-Pd alloy nanoparticles on graphene nanoplates (GNPs) anchored with sulfated zirconia nanoparticles. The results [...] Read more.
Developing highly active and durable Pt-based electrocatalysts is crucial for polymer electrolyte membrane fuel cells. This study focuses on the performance of oxygen reduction reaction (ORR) electrocatalysts composed of Pt-Pd alloy nanoparticles on graphene nanoplates (GNPs) anchored with sulfated zirconia nanoparticles. The results of field emission scanning electron microscopy and transmission electron microscopy showed that Pt-Pd and S-ZrO2 are well dispersed on the surface of the GNPs. X-ray diffraction revealed that the S-ZrO2 and Pt-Pd alloy coexist in the Pt-Pd/S-ZrO2-GNP nanocomposites without affecting the crystalline lattice of Pt and the graphitic structure of the GNPs. To evaluate the electrochemical activity and reaction kinetics for ORR, we performed cyclic voltammetry, rotating disc electrode, and EIS experiments in acidic solutions at room temperature. The findings showed that Pt-Pd/S-ZrO2-GNPs exhibited a better ORR performance than the Pt-Pd catalyst on the unsulfated ZrO2-GNP support and with Pt on S-ZrO2-GNPs and commercial Pt/C. Full article
(This article belongs to the Special Issue Two-Dimensional Materials: From Synthesis to Applications)
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46 pages, 6832 KiB  
Review
A Comprehensive Review of Bimetallic Nanoparticle–Graphene Oxide and Bimetallic Nanoparticle–Metal–Organic Framework Nanocomposites as Photo-, Electro-, and Photoelectrocatalysts for Hydrogen Evolution Reaction
by Mogwasha Dapheny Makhafola, Sheriff Aweda Balogun and Kwena Desmond Modibane
Energies 2024, 17(7), 1646; https://doi.org/10.3390/en17071646 - 29 Mar 2024
Cited by 14 | Viewed by 3339
Abstract
This review extensively discusses current developments in bimetallic nanoparticle–GO and bimetallic nanoparticle–MOF nanocomposites as potential catalysts for HER, along with their different synthesis methodologies, structural characteristics, and catalytic mechanisms. The photoelectrocatalytic performance of these catalysts was also compared based on parameters such as [...] Read more.
This review extensively discusses current developments in bimetallic nanoparticle–GO and bimetallic nanoparticle–MOF nanocomposites as potential catalysts for HER, along with their different synthesis methodologies, structural characteristics, and catalytic mechanisms. The photoelectrocatalytic performance of these catalysts was also compared based on parameters such as Tafel slope, current density, onset potential, turnover frequency, hydrogen yield, activation energy, stability, and durability. The review shows that the commonly used metal alloys in the bimetallic nanoparticle–GO-based catalysts for HERs include Pt-based alloys (e.g., PtNi, PtCo, PtCu, PtAu, PtSn), Pd-based alloys (e.g., PdAu, PdAg, PdPt) or other combinations, such as AuNi, AuRu, etc., while the most used electrolyte sources are H2SO4 and KOH. For the bimetallic nanoparticle MOF-based catalysts, Pt-based alloys (e.g., PtNi, PtCu), Pd-based alloys (e.g., PdAg, PdCu, PdCr), and Ni-based alloys (e.g., NiMo, NiTi, NiAg, NiCo) took the lead, with KOH being the most frequently used electrolyte source. Lastly, the review addresses challenges and prospects, highlighting opportunities for further optimization and technological integration of the catalysts as promising alternative photo/electrocatalysts for future hydrogen production and storage. Full article
(This article belongs to the Section A5: Hydrogen Energy)
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22 pages, 18969 KiB  
Article
Dilute Alloy Catalysts for the Synthesis of Isobutanol via the Guerbet Route: A Comprehensive Study
by Johannes Häusler, Joachim Pasel, Clemens Wöllhaf, Ralf Peters and Detlef Stolten
Catalysts 2024, 14(3), 215; https://doi.org/10.3390/catal14030215 - 21 Mar 2024
Cited by 2 | Viewed by 1912
Abstract
This study investigates the potential of bimetallic alloy catalysts, specifically Ni99Pt1, Cu99Ni1, Cu99Fe1, Fe99Pt1, and Fe99Pd1, for the synthesis of isobutanol via the [...] Read more.
This study investigates the potential of bimetallic alloy catalysts, specifically Ni99Pt1, Cu99Ni1, Cu99Fe1, Fe99Pt1, and Fe99Pd1, for the synthesis of isobutanol via the Guerbet route. The catalysts were synthesized with a doping of 1 at% Ni, Fe, Pt, and Pd in the base metals Fe, Cu, and Ni. The catalytic properties of these bimetallic alloy catalysts were explored for their potential for promoting the Guerbet reaction. The study aims to test the usability of the theoretically predicted d-band values in the synthesized bimetallic catalysts, which were prepared by means of incipient wetness impregnation, and shows that doping amounts smaller than 1 at% already significantly improved the catalytic activity of the base metals. In particular, the doping of nickel with platinum yielded an effective catalyst for the synthesis of isobutanol via the Guerbet pathway. The Ni99Pt1/C catalyst from the presented experiments had the highest Space Time Yield (STY) and is, therefore, also a promising catalyst for the hydrogen-borrowing reactions class. Full article
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17 pages, 4753 KiB  
Article
Nickel-Based Single-Atom Alloys for Methane Dehydrogenation and the Effect of Subsurface Carbon: First-Principles Investigations
by Naiyuan Dong, Tanglaw Roman and Catherine Stampfl
Catalysts 2024, 14(2), 145; https://doi.org/10.3390/catal14020145 - 16 Feb 2024
Cited by 3 | Viewed by 2374
Abstract
Using ab initio calculations, the reaction path for methane dehydrogenation over a series of Ni-based single-atom alloys (Cu, Fe, Pt, Pd, Zn, Al) and the effect that subsurface carbon at the Ni(111) surface has on the reaction barriers are investigated. Due to the [...] Read more.
Using ab initio calculations, the reaction path for methane dehydrogenation over a series of Ni-based single-atom alloys (Cu, Fe, Pt, Pd, Zn, Al) and the effect that subsurface carbon at the Ni(111) surface has on the reaction barriers are investigated. Due to the well-known problem of coking for Ni-based catalysts, the adsorption and associated physical properties of 0.25 ML, 1.0 ML, and 2 ML of carbon on the Ni(111) surface of various sites are first studied. It is found that the presence of subsurface carbon reduces the stability of the intermediates and increases the reaction barriers, thus reducing the performance of the Ni(111) catalyst. The presence of Al, Zn, and Pt is found to reduce the barriers for the CH4 → CH3 + H and CH3 → CH2 + H (Pt); and CH → C + H (Al, Zn) reactions, while Ni(111) yields the lowest barriers for the CH2 → CH + H reaction. These results thus suggest that doping the Ni surface with both Al or Zn atoms and Pt atoms, functioning as distinct active sites, may bring about an improved reactivity and/or selectivity for methane decomposition. Furthermore, the results show that there can be significant adparticle–adparticle interactions in the simulation cell, which affect the reaction energy diagram and thus highlight the importance of ensuring a common reference energy for all steps. Full article
(This article belongs to the Special Issue Application of Catalysts in CO2 Capture, Production and Utilization)
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15 pages, 5083 KiB  
Article
Ab Initio Study of Structural, Electronic, and Thermal Properties of Pt/Pd-Based Alloys
by Louise Magdalene Botha, Cecil Naphtaly Moro Ouma, Kingsley Onyebuchi Obodo, Dmitri Georgievich Bessarabov, Denis Lvovich Sharypin, Pyotr Sergeevich Varyushin and Elizaveta Ivanovna Plastinina
Condens. Matter 2023, 8(3), 76; https://doi.org/10.3390/condmat8030076 - 5 Sep 2023
Cited by 2 | Viewed by 2186
Abstract
Alloys are beneficial in numerous applications since they combine the desirable properties of different metals. In this regard, Pt/Pd alloys have been investigated as a replacement for Pt, which is the standard catalyst used in various catalytic processes. However, there are still gaps [...] Read more.
Alloys are beneficial in numerous applications since they combine the desirable properties of different metals. In this regard, Pt/Pd alloys have been investigated as a replacement for Pt, which is the standard catalyst used in various catalytic processes. However, there are still gaps in our understanding of the structural, mechanical, and thermodynamic properties of Pt/Pd alloys. This study was conducted using density functional theory (DFT) calculations to investigate the electronic, elasticity, mechanical, and thermodynamic properties of Pt/Pd alloys and compared them to pristine Pt and Pd structures. The results indicate that the considered Pt/Pd alloy structures, PtPd3, PtPd, Pt3Pd, and Pt7Pd, are energetically favourable based on their formation energies. These structures also satisfy Born’s stability criteria and are elastically stable. The phonon density of states showed that the considered Pt/Pd alloy structures are dynamically stable, with no imaginary modes present. Additionally, the Pt atom dominates at lower frequencies, while the Pd atom dominates at higher frequencies, as seen in the phonon band structure. The electronic density of states revealed that the considered Pt/Pd alloy structures have a metallic character and are non-magnetic. These findings contribute to a better understanding of the properties and stability of Pt/Pd alloy structures that are relevant in various fields, including materials science and catalysis. Full article
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32 pages, 11957 KiB  
Review
Review of the Status and Prospects of Fiber Optic Hydrogen Sensing Technology
by Changyu Shen, Zihan Xie, Zhenlin Huang, Sasa Yan, Wenbo Sui, Jun Zhou, Zhaokun Wang, Wei Han and Xianglong Zeng
Chemosensors 2023, 11(9), 473; https://doi.org/10.3390/chemosensors11090473 - 23 Aug 2023
Cited by 15 | Viewed by 4485
Abstract
With the unprecedented development of green and renewable energy sources, the proportion of clean hydrogen (H2) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible, high-performance H2 sensors to detect and monitor hydrogen concentration [...] Read more.
With the unprecedented development of green and renewable energy sources, the proportion of clean hydrogen (H2) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible, high-performance H2 sensors to detect and monitor hydrogen concentration are essential. This review discusses a variety of fiber-optic-based H2 sensor technologies since the year 1984, including: interferometer technology, fiber grating technology, surface plasma resonance (SPR) technology, micro lens technology, evanescent field technology, integrated optical waveguide technology, direct transmission/reflection detection technology, etc. These technologies have been evolving from simply pursuing high sensitivity and low detection limits (LDL) to focusing on multiple performance parameters to match various application demands, such as: high temperature resistance, fast response speed, fast recovery speed, large concentration range, low cross sensitivity, excellent long-term stability, etc. On the basis of palladium (Pd)-sensitive material, alloy metals, catalysts, or nanoparticles are proposed to improve the performance of fiber-optic-based H2 sensors, including gold (Au), silver (Ag), platinum (Pt), zinc oxide (ZnO), titanium oxide (TiO2), tungsten oxide (WO3), Mg70Ti30, polydimethylsiloxane (PDMS), graphene oxide (GO), etc. Various microstructure processes of the side and end of optical fiber H2 sensors are also discussed in this review. Full article
(This article belongs to the Special Issue Gas Detection Sensors for On-Chip Applications)
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13 pages, 2483 KiB  
Article
Self-Supported 3D PtPdCu Nanowires Networks for Superior Glucose Electro-Oxidation Performance
by Kaili Wang, Shuang He, Bowen Zhang, Zhen Cao, Tingting Zhou, Jia He and Ganghui Chu
Molecules 2023, 28(15), 5834; https://doi.org/10.3390/molecules28155834 - 2 Aug 2023
Cited by 8 | Viewed by 1814
Abstract
The development of non-enzymatic and highly active electrocatalysts for glucose oxidation with excellent durability for blood glucose sensors has aroused widespread concern. In this work, we report a fast, simple, and low-cost NaBH4 reduction method for preparing ultrafine ternary PtPdCu alloy nanowires [...] Read more.
The development of non-enzymatic and highly active electrocatalysts for glucose oxidation with excellent durability for blood glucose sensors has aroused widespread concern. In this work, we report a fast, simple, and low-cost NaBH4 reduction method for preparing ultrafine ternary PtPdCu alloy nanowires (NWs) with a 3D network nanostructure. The PtPdCu NWs catalyst presents significant efficiency for glucose oxidation-reduction (GOR), reaching an oxidative peak-specific activity of 0.69 mA/cm2, 2.6 times that of the Pt/C catalyst (0.27 mA/cm2). Further reaction mechanism investigations show that the NWs have better conductivity and smaller electron transfer resistance. Density functional theory (DFT) calculations reveal that the alloying effect of PtPdCu could effectively enhance the adsorption energy of glucose and reduce the activation energy of GOR. The obtained NWs also show excellent stability over 3600 s through a chronoamperometry test. These self-supported ultrafine PtPdCu NWs with 3D networks provide a new functional material for building blood glucose sensors and direct glucose fuel cells. Full article
(This article belongs to the Special Issue Recent Progress in Nanomaterials in Electrochemistry)
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38 pages, 3801 KiB  
Review
Review on the Chemistry of [M(NH3)n](XO4)m (M = Transition Metal, X = Mn, Tc or Re, n = 1–6, m = 1–3) Ammine Complexes
by Raj Narain Mehrotra
Inorganics 2023, 11(7), 308; https://doi.org/10.3390/inorganics11070308 - 20 Jul 2023
Cited by 9 | Viewed by 4336
Abstract
The preparation of ammine complexes of transition metals having oxidizing anions such as permanganate and perrhenate ions is a great challenge due to possible reactions between ammonia and oxidizing anions during the synthesis of these materials. However, it has an important role in [...] Read more.
The preparation of ammine complexes of transition metals having oxidizing anions such as permanganate and perrhenate ions is a great challenge due to possible reactions between ammonia and oxidizing anions during the synthesis of these materials. However, it has an important role in both the development of new oxidants in organic chemistry and especially in the preparation of mixed-metal oxide catalyst precursors and metal alloys for their controlled temperature decomposition reactions. Therefore, in this paper, synthetic procedures to prepare ammonia complexes of transition metal permanganate, pertechnetate, and perrhenate (the VIIB group tetraoxometallates) salts have been comprehensively reviewed. The available data about these compounds’ structures and spectroscopic properties, including the presence of hydrogen bonds that act as redox reaction centers during thermal decomposition, are given and evaluated in detail. The nature of the thermal decomposition products has also been summarized. The available information about the role of the ammine complexes of transition metal permanganate salts in organic oxidation reactions, such as the oxidation of benzyl alcohols and regeneration of oxo-compounds from oximes and phenylhydrazones, including the kinetics of these processes, has also been collected. Their physical and chemical properties, including the thermal decomposition characteristics of known diammine (Ag(I), Cd, Zn, Cu(II), Ni(II)), triammine (Ag(I)), and simple or mixed ligand tetraammine (Cu(II), Zn, Cd, Ni(II), Co(II), Pt(II), Pd(II), Co(III)), Ru(III), pentaammine (Co(III), Cr(III), Rh(III) and Ir(III)), and hexaammine (Ni(II), Co(III), Cr(III)) complexes of transition metals with tetraoxometallate(VII) anions (M = Mn, Tc and Re), have been summarized. The preparation and properties of some special mixed ligand/anion/cation-containing complexes, such as [Ru(NH3)4(NO)(H2O)](ReO4)2, [Co(NH3)5(H2O)](ReO4)2, [Co(NH3)5X](MnO4)2 (X = Cl, Br), [Co(NH3)6]Cl2(MnO4), [Co(NH3)5ReO4]X2 (X = Cl, NO3, ClO4, ReO4), and K[Co(NH3)6]Cl2(MnO4)2, are also included. Full article
(This article belongs to the Special Issue Metal Complexes with N-donor Ligands)
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17 pages, 20929 KiB  
Article
Pd–Co-Based Electrodes for Hydrogen Production by Water Splitting in Acidic Media
by Bernardo Patella, Claudio Zanca, Fabrizio Ganci, Sonia Carbone, Francesco Bonafede, Giuseppe Aiello, Rosario Miceli, Filippo Pellitteri, Philippe Mandin and Rosalinda Inguanta
Materials 2023, 16(2), 474; https://doi.org/10.3390/ma16020474 - 4 Jan 2023
Cited by 6 | Viewed by 2881
Abstract
To realize the benefits of a hydrogen economy, hydrogen must be produced cleanly, efficiently and affordably from renewable resources and, preferentially, close to the end-users. The goal is a sustainable cycle of hydrogen production and use: in the first stage of the cycle, [...] Read more.
To realize the benefits of a hydrogen economy, hydrogen must be produced cleanly, efficiently and affordably from renewable resources and, preferentially, close to the end-users. The goal is a sustainable cycle of hydrogen production and use: in the first stage of the cycle, hydrogen is produced from renewable resources and then used to feed a fuel cell. This cycle produces no pollution and no greenhouse gases. In this context, the development of electrolyzers producing high-purity hydrogen with a high efficiency and low cost is of great importance. Electrode materials play a fundamental role in influencing electrolyzer performances; consequently, in recent years considerable efforts have been made to obtain highly efficient and inexpensive catalyst materials. To reach both goals, we have developed electrodes based on Pd–Co alloys to be potentially used in the PEMEL electrolyzer. In fact, the Pd–Co alloy is a valid alternative to Pt for hydrogen evolution. The alloys were electrodeposited using two different types of support: carbon paper, to fabricate a porous structure, and anodic alumina membrane, to obtain regular arrays of nanowires. The goal was to obtain electrodes with very large active surface areas and a small amount of material. The research demonstrates that the electrochemical method is an ideal technique to obtain materials with good performances for the hydrogen evolution reaction. The Pd–Co alloy composition can be controlled by adjusting electrodeposition parameters (bath composition, current density and deposition time). The main results concerning the fabrication process and the characterization are presented and the performance in acid conditions is discussed. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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17 pages, 4937 KiB  
Article
Ultra-Small Nanoparticles of Pd-Pt-Ni Alloy Octahedra with High Lattice Strain for Efficient Oxygen Reduction Reaction
by Yuanyan Luo, Wenhua Lou, Huiyan Feng, Zhihang Liu, Qiuyan Chen, Guizhen Liao, Xiaoting Huang, Panagiotis Tsiakaras and Peikang Shen
Catalysts 2023, 13(1), 97; https://doi.org/10.3390/catal13010097 - 3 Jan 2023
Cited by 8 | Viewed by 2963
Abstract
The design and synthesis of ultra-small-sized Pt-based catalyst with specific effects for enhancing the oxygen reduction reaction (ORR) is an effective way to improve the utilization of Pt. Herein, Pt-Pd-Ni octahedra nanoparticles characterized by the ultra-small size of 4.71 nm were synthesized by [...] Read more.
The design and synthesis of ultra-small-sized Pt-based catalyst with specific effects for enhancing the oxygen reduction reaction (ORR) is an effective way to improve the utilization of Pt. Herein, Pt-Pd-Ni octahedra nanoparticles characterized by the ultra-small size of 4.71 nm were synthesized by a Pd seed-inducing-growth route. Initially, Pd nanocubes were synthesized under solvothermal conditions; subsequently, Pt-Ni was deposited in the Pd seed solution. The Pd seeds were oxidized into Pd2+ and combined with Pt2+ and Ni2+ in the solution and finally formed the ternary alloy small-sized octahedra. In the synthesis process of the ultra-small Pt-Pd-Ni octahedra, Pd nanocube seed played an important role. In addition, the size of the Pt-Pd-Ni octahedra could be regulated by adjusting the concentration rate of Pt-Ni. The ultra-small Pt-Pd-Ni octahedra formation by depositing Pt-Ni with a feeding ratio of 2:1 showed good ORR activity, and the high half-wave potential was 0.933 V. In addition, the Pt-Pd-Ni octahedra showed an enhanced mass activity of 0.93 A mg−1 Pt+Pd in ORR, which was 5.81 times higher than commercial Pt/C. The theoretical calculation shows that compared to Pt/C, the small-sized ternary alloy octahedra had an obvious contraction strain effect (contraction rate: 3.49%). The alloying effect affected the d-band center of the Pt negative shift. In the four-electron reaction, Pt-Pd-Ni ultra-small octahedra exhibited the lowest overpotential, resulting in the adsorption performance to become optimized. Therefore, the Pd seed-inducing-growth route provides a new idea for exploring the synthesis of small-sized nanoparticle catalysts. Full article
(This article belongs to the Special Issue Electrocatalysts for Oxidation-Reduction Reactions)
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