Showing papers on "Noble metal published in 2022"

Non-Noble Plasmonic Metal-Based Photocatalysts.

Abstract: Solar-to-chemical energy conversion via heterogeneous photocatalysis is one of the sustainable approaches to tackle the growing environmental and energy challenges. Among various promising photocatalytic materials, plasmonic-driven photocatalysts feature prominent solar-driven surface plasmon resonance (SPR). Non-noble plasmonic metals (NNPMs)-based photocatalysts have been identified as a unique alternative to noble metal-based ones due to their advantages like earth-abundance, cost-effectiveness, and large-scale application capability. This review comprehensively summarizes the most recent advances in the synthesis, characterization, and properties of NNPMs-based photocatalysts. After introducing the fundamental principles of SPR, the attributes and functionalities of NNPMs in governing surface/interfacial photocatalytic processes are presented. Next, the utilization of NNPMs-based photocatalytic materials for the removal of pollutants, water splitting, CO2 reduction, and organic transformations is discussed. The review concludes with current challenges and perspectives in advancing the NNPMs-based photocatalysts, which are timely and important to plasmon-based photocatalysis, a truly interdisciplinary field across materials science, chemistry, and physics.

Realizing Negatively Charged Metal Atoms through Controllable d‐Electron Transfer in Ternary Ir1−xRhxSb Intermetallic Alloy for Hydrogen Evolution Reaction

Abstract: Alloying noble metals with non‐noble metals is a promising method to fabricate catalysts, with the advantages of reduced noble metal usage and excellent activity. In this work, electron‐abundant Ir/Rh sites, as highly active centers for the hydrogen evolution reaction (HER), are realized by fabricating Ir1−xRhxSb alloys through the arc‐melting method. The electron transfer from Sb to Ir/Rh makes the latter negatively charged, leading to considerably optimized adsorption for active H species during HER. As a result, the Ir1−xRhxSb alloy exhibits outstanding activity for HER, with an optimized overpotential of 22 mV at 10 mA cm–2 and a Tafel slope of 47.6 mV dec–1. This work provides insights into highly active alloys and sheds light on the utilization of electron‐abundant metal atoms.

Amorphizing noble metal chalcogenide catalysts at the single-layer limit towards hydrogen production

Abstract: Rational design of noble metal catalysts with the potential to leverage efficiency is vital for industrial applications. Such an ultimate atom-utilization efficiency can be achieved when all noble metal atoms exclusively contribute to catalysis. Here, we demonstrate the fabrication of a wafer-size amorphous PtSex film on a SiO2 substate via a low-temperature amorphization strategy, which offers single-atom-layer Pt catalysts with high atom-utilization efficiency (~26 wt%). This amorphous PtSex (1.2 < x < 1.3) behaves as a fully activated surface, accessible to catalytic reactions, and features a nearly 100% current density relative to a pure Pt surface and reliable production of sustained high-flux hydrogen over a 2 inch wafer as a proof-of-concept. Furthermore, an electrolyser is demonstrated to generate a high current density of 1,000 mA cm−2. Such an amorphization strategy is potentially extendable to other noble metals, including the Pd, Ir, Os, Rh and Ru elements, demonstrating the universality of single-atom-layer catalysts. The scarcity and high price of noble metal catalysts pose critical challenges for the chemical industry, and finding strategies that ensure complete atom efficiency has become a pivotal endeavour. This work introduces the fabrication of amorphous single-layer PtSex catalysts for the hydrogen evolution reaction with high atom-utilization efficiency.

Electrochemically Reconstructed Cu‐FeOOH/Fe3O4 Catalyst for Efficient Hydrogen Evolution in Alkaline Media

Abstract: Surface self‐reconstruction via incorporating an amorphous structure on the surface of a catalyst can induce abundant defects and unsaturated sites for enhanced hydrogen evolution reaction (HER) activity. Herein, an electrochemical activation method is proposed to reconstruct the surface of a Cu‐Fe3O4 catalyst. Following a “dissolution–redeposition” path, the defective FeOOH is formed under potential stimulation on the surface of the Cu‐Fe3O4 precursor during the electrochemical activation process. This Cu‐FeOOH/Fe3O4 catalyst exhibits excellent stability as well as extremely low overpotential toward the alkaline HER (e.g., 129 and 285 mV at the large current densities of −100 and 500 mA cm−2, respectively), much superior to the Pt/C catalyst. The experimental and density functional theory calculation results demonstrate that the Cu‐FeOOH/Fe3O4 catalyst has abundant oxygen vacancies, featuring optimized surface chemical composition and electronic structure for improving the active sites and intrinsic activity. Introducing defective FeOOH on the surface of a Cu‐Fe3O4 catalyst by means of an electrochemical activation method decreases the energy barrier of both H2O dissociation and H2 generation. Such a surface self‐reconstruction strategy provides a new avenue toward the production of efficient non‐noble metal catalysts for the HER.

A Review on MXene Synthesis, Stability, and Photocatalytic Applications.

Abstract: Photocatalytic water splitting, CO2 reduction, and pollutant degradation have emerged as promising strategies to remedy the existing environmental and energy crises. However, grafting of expensive and less abundant noble-metal cocatalysts on photocatalyst materials is a mandatory practice to achieve enhanced photocatalytic performance owing to the ability of the cocatalysts to extract electrons efficiently from the photocatalyst and enable rapid/enhanced catalytic reaction. Hence, developing highly efficient, inexpensive, and noble-metal-free cocatalysts composed of earth-abundant elements is considered as a noteworthy step toward considering photocatalysis as a more economical strategy. Recently, MXenes (two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides) have shown huge potential as alternatives for noble-metal cocatalysts. MXenes have several excellent properties, including atomically thin 2D morphology, metallic electrical conductivity, hydrophilic surface, and high specific surface area. In addition, they exhibit Gibbs free energy of intermediate H atom adsorption as close to zero and less than that of a commercial Pt-based cocatalyst, a Fermi level position above the H2 generation potential, and an excellent ability to capture and activate CO2 molecules. Therefore, there is a growing interest in MXene-based photocatalyst materials for various photocatalytic events. In this review, we focus on the recent advances in the synthesis of MXenes with 2D and 0D morphologies, the stability of MXenes, and MXene-based photocatalysts for H2 evolution, CO2 reduction, and pollutant degradation. The existing challenges and the possible future directions to enhance the photocatalytic performance of MXene-based photocatalysts are also discussed.

Controllable Synthesis of Web-Footed PdCu Nanosheets and Their Electrocatalytic Applications.

Abstract: Morphological control of noble-metal-based nanocrystals has attracted enormous attention because their catalytic behaviors can be optimized well by adjusting the size and shape. Herein, the controllable synthesis of web-footed PdCu nanosheets via a facile surfactant-free method is reported. It is discovered that the Cu(II) precursor in this synthetic system displays a critical role in growing branches along the lateral of nanosheets. This work demonstrates a Pd-based alloy nanoarchitecture for efficient and stable electrocatalysis of both ethanal and formic acid oxidation reactions.

Noble Metal Based Electrocatalysts for Alcohol Oxidation Reactions in Alkaline Media

Abstract: Alkaline direct alcohol fuel cells (ADAFCs) represent an attractive alternative to hydrogen fuel cells for the more convenient storage, transportation, and lower cost of alcohols (e.g., methanol and ethanol) when compared with compressed hydrogen. However, the anode alcohol oxidation reaction (AOR) is generally plagued with high overpotential and sluggish kinetics, and often requires noble metal‐based electrocatalysts to accelerate the reaction kinetics. To this end, the development of efficient AOR electrocatalysts with high mass activity (MA), high durability, high Faradaic efficiency (FE), and low overpotential is central for realizing practical ADAFCs. Here, in this minireview, a brief introduction of the fundamental challenges associated with AOR in alkaline electrolyte, the key performance metrics, and the evaluation protocols for benchmarking AOR electrocatalysts are presented, followed by a summary of the recent advances in the noble‐metal based AOR electrocatalysts (e.g., Pt, Pd, and Rh) with an emphasis on the design criteria for improving the specific activity and electrochemical surface area to ultimately deliver high MA while at the same time ensuring long term durability. The strategies to enhance FE and lower overpotential will also be discussed. Last, it is concluded with a brief perspective on the key challenges and future opportunities.

Efficient and stable noble-metal-free catalyst for acidic water oxidation

Abstract: Developing non-noble catalysts with superior activity and durability for oxygen evolution reaction (OER) in acidic media is paramount for hydrogen production from water. Still, challenges remain due to the inadequate activity and stability of the OER catalyst. Here, we report a cost-effective and stable manganese oxybromide (Mn7.5O10Br3) catalyst exhibiting an excellent OER activity in acidic electrolytes, with an overpotential of as low as 295 ± 5 mV at a current density of 10 mA cm-2. Mn7.5O10Br3 maintains good stability under operating conditions for at least 500 h. In situ Raman spectroscopy, X ray absorption near edge spectroscopy, and density functional theory calculations confirm that a self-oxidized surface with enhanced electronic transmission capacity forms on Mn7.5O10Br3 and is responsible for both the high catalytic activity and long-term stability during catalysis. The development of Mn7.5O10Br3 as an OER catalyst provides crucial insights into the design of non-noble metal electrocatalysts for water oxidation.

New Trends in Nanoarchitectured SERS Substrates: Nanospaces, 2D Materials, and Organic Heterostructures.

Abstract: This article reviews recent fabrication methods for surface-enhanced Raman spectroscopy (SERS) substrates with a focus on advanced nanoarchitecture based on noble metals with special nanospaces (round tips, gaps, and porous spaces), nanolayered 2D materials, including hybridization with metallic nanostructures (NSs), and the contemporary repertoire of nanoarchitecturing with organic molecules. The use of SERS for multidisciplinary applications has been extensively investigated because the considerably enhanced signal intensity enables the detection of a very small number of molecules with molecular fingerprints. Nanoarchitecture strategies for the design of new NSs play a vital role in developing SERS substrates. In this review, recent achievements with respect to the special morphology of metallic NSs are discussed, and future directions are outlined for the development of available NSs with reproducible preparation and well-controlled nanoarchitecture. Nanolayered 2D materials are proposed for SERS applications as an alternative to the noble metals. The modern solutions to existing limitations for their applications are described together with the state-of-the-art in bio/environmental SERS sensing using 2D materials-based composites. To complement the existing toolbox of plasmonic inorganic NSs, hybridization with organic molecules is proposed to improve the stability of NSs and selectivity of SERS sensing by hybridizing with small or large organic molecules.

Interfacial Reduction Nucleation of Noble Metal Nanodots on Redox-Active Metal-Organic Frameworks for High-Efficiency Electrocatalytic Conversion of Nitrate to Ammonia.

Abstract: Electrochemically converting nitrate to ammonia is a promising route to realize artificial nitrogen recycling. However, developing highly efficient electrocatalysts is an ongoing challenge. Herein, we report the construction of stable and redox-active zirconium metal-organic frameworks (Zr-MOFs) based on Zr6 nanoclusters and redox-reversible tetrathiafulvalene (TTF) derivatives as inorganic nodes and organic linkers, respectively. The redox-active Zr-MOF can facilitate the in situ reduction of noble metal precursors free of external reductants and realize the uniform nucleation of noble metal nanodots (NDs) on Zr-MOF, achieving the preparation of M-NDs/Zr-MOF (M = Pd, Ag, or Au). The highly porous Zr-MOF with good conductivity can facilitate the mass transfer process. Among the M-NDs/Zr-MOF catalysts, Pd-NDs/Zr-MOF exhibits the highest electrocatalytic activity, delivering a NH3 yield of 287.31 mmol·h-1·g-1cat. and a Faradaic efficiency of 58.1%. The proposed interfacial reduction nucleation strategy for anchoring M NDs on Zr-MOFs can be applied to other challenging energy conversion reactions.

Boosting oxygen evolution of layered double hydroxide through electronic coupling with ultralow noble metal doping.

Abstract: Electrocatalytic water oxidation is a rate-determining step in the water splitting process; however, its efficiency is significantly hampered by the limitations of cost-effective electrocatalysts. Here, an advanced Co(OH)2 electrocatalyst with ultralow iridium (Ir) doping is developed to enable outstanding oxygen evolution reaction (OER) properties; that is, in a 1 M KOH medium, an overpotential of only 262 mV is required to achieve a current density of 10 mA cm-2, and a small Tafel slope of 66.9 mV dec-1 is achieved, which is markedly superior to that of the commercial IrO2 catalyst (301 mV@10 mA cm-2; 66.9 mV dec-1). Through the combination of experimental data and a mechanism study, it is disclosed that the high intrinsic OER activity results from the synergistic electron coupling of oxidized Ir and Co(OH)2, which significantly moderate the adsorption energy of the intermediates. Moreover, we have also synthesized Ru-Co(OH)2 nanosheets and demonstrated the universal syntheses of Ir-doped CoM (M = Ni, Fe, Mn, and Zn) layered double hydroxides (LDHs).

Bridging the Charge Accumulation and High Reaction Order for High‐Rate Oxygen Evolution and Long Stable Zn‐Air Batteries

Abstract: Combining noble metals with nonnoble metals is an attractive strategy to balance the activity and cost of electrocatalysts. However, a guiding principle for selecting suitable nonnoble metals is still lacking. Herein, a thorough mechanistic study on the platform oxygen evolution reaction (OER) electrocatalyst of Ir@Co3O4 to deeply understand the synergy between Ir and Co3O4 for the boosted OER has been carried out. It is demonstrated that the pseudocapacitive feature of Co3O4 plays a key role in accumulating sufficient positive charge [Q], while the Ir sites are responsible for achieving a high reaction order (β), synergistically contributing to the high OER activity of Ir@Co3O4 through the rate law equation. Specifically, Ir@Co3O4 displays a low overpotential of 280 mV at 10 mA cm−2 with a small Ir loading of 1.4 wt%. Ir@Co3O4 is further applied to Zn‐air batteries, which enables a low charging potential and thus alleviates the oxidative corrosion of the air electrode, leading to improved cycle stability of 210 h at 20 mA cm−2. This work demonstrates that anchoring active noble metal sites (for high β) on pseudocapacitive supports (for high [Q]) is highly favorable to the OER process, providing a clear guidance for boosting the utilization of noble metals in electrocatalysis.

H2-production and electron-transfer mechanism of noble-metal-free WO3@ZnIn2S4 S-scheme heterojunction photocatalyst

Abstract: Solar-driven hydrogen production can alleviate ever-growing energy crisis, but developing affordable and efficient photocatalysts is challenging. We here report a noble-metal-free WO3@ZnIn2S4 S-scheme heterojunction photocatalyst with ZnIn2S4 nanosheets vertically growing...

Formic Acid Dehydrogenation Using Noble-Metal Nanoheterogeneous Catalysts: Towards Sustainable Hydrogen-Based Energy

Abstract: The need for sustainable energy sources is now more urgent than ever, and hydrogen is significant in the future of energy. However, several obstacles remain in the way of widespread hydrogen use, most of which are related to transport and storage. Dilute formic acid (FA) is recognized asa a safe fuel for low-temperature fuel cells. This review examines FA as a potential hydrogen storage molecule that can be dehydrogenated to yield highly pure hydrogen (H2) and carbon dioxide (CO2) with very little carbon monoxide (CO) gas produced via nanoheterogeneous catalysts. It also present the use of Au and Pd as nanoheterogeneous catalysts for formic acid liquid phase decomposition, focusing on the influence of noble metals in monometallic, bimetallic, and trimetallic compositions on the catalytic dehydrogenation of FA under mild temperatures (20–50 °C). The review shows that FA production from CO2 without a base by direct catalytic carbon dioxide hydrogenation is far more sustainable than existing techniques. Finally, using FA as an energy carrier to selectively release hydrogen for fuel cell power generation appears to be a potential technique.

Tailoring noble metal nanoparticle designs to enable sensitive lateral flow immunoassay

Abstract: Lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters is a popular point-of-care diagnostic technique. However, given the weak absorbance of traditional 20-40 nm spherical AuNPs, their sensitivity is low, which greatly limits the wide application of AuNP-based LFIA. With the rapid advances in materials science and nanotechnology, the synthesis of noble metal nanoparticles (NMNPs) has enhanced physicochemical properties such as optical, plasmonic, catalytic, and multifunctional activity by simply engineering their physical parameters, including the size, shape, composition, and external structure. Using these engineered NMNPs as an alternative to traditional AuNPs, the sensitivity of LFIA has been significantly improved, thereby greatly expanding the working range and application scenarios of LFIA, particularly in trace analysis. Therefore, in this review, we will focus on the design of engineered NMNPs and their demonstration in improving LFIA. We highlight the strategies available for tailoring NMNP designs, the effect of NMNP engineering on their performance, and the working principle of each engineering design for enhancing LFIA. Finally, current challenges and future improvements in this field are briefly discussed.

Reduction of 4-nitrophenol using green-fabricated metal nanoparticles

Abstract: Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research. This review focuses on the basic perceptions of the green synthesis of metal nanoparticles and their supported-catalyst-based reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The mechanisms for the formation of these nanoparticles and the catalytic reduction of 4-NP are discussed. Furthermore, the parameters that need to be considered in the catalytic efficiency calculations and perspectives for future studies are also discussed.

Maximizing noble metal utilization in solid catalysts by control of nanoparticle location

Abstract: Maximizing the utilization of noble metals is crucial for applications such as catalysis. We found that the minimum loading of platinum for optimal performance in the hydroconversion of n-alkanes for industrially relevant bifunctional catalysts could be reduced by a factor of 10 or more through the rational arranging of functional sites at the nanoscale. Intentionally depositing traces of platinum nanoparticles on the alumina binder or the outer surface of zeolite crystals, instead of inside the zeolite crystals, enhanced isomer selectivity without compromising activity. Separation between platinum and zeolite acid sites preserved the metal and acid functions by limiting micropore blockage by metal clusters and enhancing access to metal sites. Reduced platinum nanoparticles were more active than platinum single atoms strongly bonded to the alumina binder. Description Better on the outside One way to maximize the activity of scarce and costly noble metals in catalysis is to use small cluster or even single atoms on metal oxide supports. Bifunctional platinum and zeolite catalysts are used industrially in alkane hydroconversion. Cheng et al. show that the amount of platinum used could be reduced and isomer selectivity improved when the catalyst preparation created platinum clusters on the surface of zeolite or its alumina binder, rather than in the interior of the zeolite channels. Preparations that would have formed single-atom catalysts were less active because the platinum ions adsorbed on the alumina surface were more difficult to reduce. —PDS Isomer selectivity in alkane hydroconversion improves when platinum clusters are located on rather than in zeolites.