Noble Materials Research Articles

Tailoring the oxygen vacancies and electronic structures of the hex-WO3 (1 0 0) crystal plane with heteroatoms for enhanced hydrogen evolution performance

Due to the difficulty of developing noble materials for large-scale applications, transition metal oxide materials have become popular alternatives for the hydrogen evolution reaction. However, compared to commercial Pt/C, poor conductivity and hydrogen evolution activity are common for transition metal oxides, including WO3-x-based semiconductors, so it is therefore necessary to ameliorate the electrode self-properties to be suitable for H2 production. Here, different ratios of S2- and Ni2+ salts are introduced into hexagonal WO3 and Ni0.4WO3-xSx is prepared successfully after oxygen vacancies and WOS and Ni–W-O bonds are formed on the surface of the Ni0.4WO3-xSx nanorods. The X-ray photoelectron, Raman and electrochemical impedance spectroscopy results show that the incorporation of Ni and S atoms can increase the number of oxygen vacancies and the conductivity for hydrogen evolution, simultaneously demonstrating that the WOS and NiWO bonds are the main active sites of the Ni0.4WO3-xSx nanorods. Density functional theory calculations further indicate that the ΔGH* of NiWO3-xSx is closer to 20 % commercial Pt/C. The Tafel slope reduces to 87.3 mV/dec when approaching the Volmer–Heyrovsky kinetic mechanism reaction. Finally, the onset potential is 53 mV. The overpotential is 173 mV at 10 mA/cm2, which is 68 % lower compared to hexagonal WO3.

A 2D/2D heterojunction of ultrathin Pd nanosheet/MXene towards highly efficient methanol oxidation reaction: the significance of 2D material nanoarchitectonics.

Two-dimensional (2D) Pd nanosheet-based catalysts have recently garnered widespread attention due to their high atom utilization efficiency. However, their catalytic ability and structural stability still require significant enhancement before they can be widely applied. In this study, we presented the rational design and controllable fabrication of a novel 2D/2D heterojunction, which consists of ultrathin Pd nanosheets (NSs) grown on the Ti3C2Tx MXene surface (Pd NSs/MXene). This heterostructure was achieved through a robust and convenient stereo-assembly strategy. The newly developed Pd NSs/MXene heterojunction not only provides numerous exposed active Pd atoms with an optimized electronic structure but also enables an intimate Pd/MXene interfacial interaction, ensuring a stable hybrid configuration. Consequently, the resulting Pd NSs/MXene heterojunction exhibits exceptional methanol oxidation properties. It possesses a large electrochemically active surface area, high mass and specific activities, and a long operating life, which are significantly superior to those of traditional Pd nanoparticle/carbon and Pd nanosheet/carbon catalysts. Theoretical simulations further reveal strong electronic interactions between the Pd nanosheet and MXene, which dramatically enhance the adsorption energy of the Pd component and simultaneously lower its d-band center. As a result, the Pd NSs/MXene heterojunction is less susceptible to CO poisoning. This work introduces a new 2D/2D heterojunction based on MXene and noble metallic materials and holds significance for the development of other novel heterojunctions, particularly within the realm of 2D material nanoarchitectonics.

Effect of pore mesostructure on the electrooxidation of glycerol on Pt mesoporous catalysts

Valuable chemicals such as glycerate, in addition to hydrogen, can be obtained from the controlled electrooxidation of glycerol using suitable highly active, mesoporous platinum catalysts.

Dealloying of Pt1Bi2 intermetallic toward optimization of electrocatalysis on a Bi-continuous nanoporous core-shell structure.

Noble metal nanoporous materials hold great potential in the field of catalysis, owing to their high open structures and numerous low coordination surface sites. However, the formation of porous nanoparticles is restricted by particle size. Herein, we utilized a Pt1Bi2 intermetallic nanocatalyst to develop a dealloying approach for preparing nanoparticles with a bi-continuous porous and core-shell structure and proposed a mechanism for the formation of pores. The particle size used to form the porous structure can be <10 nm, which enhances the nanocatalyst's performance for the oxygen reduction reaction (ORR). This study provides a new understanding of the formation of porous materials via a dealloying approach.

Residual stresses of explosively welded bimetal studied by hard X-ray diffraction

Geothermal heat from the Earth`s crust is a source of natural and renewable energy. This energy can be extracted and used for generating electricity and heating of houses in the winter months. However, in order to extract energy from a well, we need to use material that can sustain contact with geothermal steam and is resistant to corrosion of the geothermal fluid and non-condensing gases such as hydrogen sulfide (H2S) and carbon dioxide (CO2), chloride ions (Cl−), and hydrogen fluoride (HF). An interesting alternative to today's materials are bimetals, composed of two different materials where the layer in contact with the aggressive environment is made of a noble material, while the outer layer (typically low-carbon steel) strengthens the composite and additionally provides good weldability.This paper presents the microstructure, phase composition, and distribution of residual stresses of the bimetallic system nickel-chromium-molybdenum alloy (Alloy 625) cladded on the ferritic pressure vessel steel P355NH base material.The bimetal has been prepared by explosion welding and is its use is geared for transport of highly corrosive media and as a material for heat exchangers, condensers, etc.

CuBi bimetallic aerogel as peroxidase-like nanozyme for total antioxidant capacity colorimetric detection

Metal aerogel with porous structure and interlocking pore channel can provide abundant active sites to boost the peroxidase (POD)-like activity for high-performance colorimetric analysis of food quality. Herein, CuBi bimetallic aerogels with different atomic ratio (Cu1Bi9, Cu5Bi5 and Cu9Bi1) were fabricated by a facile one-step reduction strategy, and the POD-like activity of the synthesized CuBi bimetallic aerogels was studied. The specific activity of Cu9Bi1 aerogel was significantly enhanced due to the Bi-doping strategy. Through comparing the Km values we find that CuBi bimetallic aerogel can be used as a cheap alternative to equivalent noble metal materials for biosensor applications. Then, the optimized nanozyme was exploited to establish a colorimetric method for the total antioxidant capacity (TAC) by utilizing ascorbic acid (AA) as a representative antioxidant model. The linear range and limit of detection (LOD) were determined to be 300–900 μM and 59.4 μM, respectively, the wide detection range simplifies sample pre-treatment steps. Additionally, the method also demonstrated good feasibility for the TAC of food samples. The current study expands new fields for the application of metal aerogels and successfully developed macroscopic nanozymes with a convenient application, facile preparation and low cost.

A Systematical Comparison of Catalytic Behavior of NM/γ-Al2O3 (NM = Ru, Rh, Pt, Pd, Au, Ir) on 1,2-Dichloroethane Oxidation: Distributions of By-Products and Reaction Mechanism

Understanding the reaction path and mechanism of chlorinated volatile organic compound (CVOC) destruction is important for designing efficient catalysts, especially for the application of noble metal-based materials. Herein, several typical noble metals, Ru, Rh, Pt, Pd, Au, and Ir, supported on γ-Al2O3 catalysts were synthesized by the hydrazine hydrate reduction method for 1,2-dichloroethane (1,2-DCE) elimination. Various character measurements were conducted, and the results suggest that the high-valence state of noble metals is beneficial for the 1,2-DCE reaction as it enables the enhancement of the mobility of the surficial active oxygen species of catalysts. Among the noble metals, Ru/γ-Al2O3 expresses superior catalytic reactivity, with a 90% pollutant conversion rate at 337 °C, and competitive CO2 selectivity, 99.15% at the temperature of total oxidation. The distribution of by-products and the degradation routes were analyzed online by GC-ECD and in situ diffuse reflectance infrared spectroscopy, which may provide helpful insight for the future application of noble metal-based catalysts for CVOC elimination in industrial fields.

0D/2D Co3O4/Ti3C2 MXene Composite: A Dual-Functional Electrocatalyst for Energy-Saving Hydrogen Production and Urea Oxidation

Electrocatalytic water splitting to produce hydrogen (H2) is a sustainable way of meeting energy demands at no environmental cost. However, the sluggish anodic reaction imposes a considerable overpotential requirement. By contrast, the electrocatalytic urea oxidation reaction offers the prospect of energy-saving H2 production together with urea-rich wastewater purification. In this work, a 0D/2D Co3O4/Ti3C2 MXene composite was synthesized by a simple solution reaction approach under mild conditions and applied as an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) in basic medium (1 M KOH+0.5 M urea). The Co3O4/Ti3C2 MXene electrodes delivered a current density of 10 mA cm–2 at an overpotential of 124 mV for HER and required 1.40 V to reach 10 mA cm–2 for UOR. The hybrid catalyst could maintain high activity after 40 h continuous catalytic reaction for both UOR and HER. Its catalytic performance was significantly improved compared to that of pure Ti3C2 MXene and Co3O4 solving the problem of insufficient exposure of active sites caused by too large particle size and agglomeration of Co3O4 particles. Notably, Co3O4/Ti3C2 MXene was applied as a bifunctional catalyst for overall urea-containing water splitting, and showed certain energy saving advantages compared with other reported Co-based catalysts. This work provides a strategy for application other than noble metal-based electrode materials for urea-containing wastewater purification coupled with H2 production.

High-efficiency broadband perfect absorber based on a multilayered pyramid structure

In this paper, an ultra-broadband perfect absorber based on a four-layer pyramid metamaterial and a metal insulator metal (MIM) structure has been demonstrated and investigated. Finite-difference time-domain (FDTD) results indicate that the absorption originates from localized surface plasmons and waveguide mode resonance effect. An average absorption of 96.18 % with bandwidth ranging from 308 nm to 2387 nm was achieved, and the average absorption in the entire wave band (200–2800 nm) was approximately 94.64%. The results of the impedance matching theory are consistent with the FDTD simulation. Polarization insensitivity was investigated by studying the absorption characteristic of TE and TM polarizations. The effect of top and bottom materials was investigated and compared in detail. Moreover, by adjusting the geometrical size, the absorption performance can be fine- tuned. In addition, the proposed broadband absorber exhibited excellent absorption stability and environmental refractive index tolerance. Without noble metal materials, the proposed structure can reduce the fabrication costs. We believe that the proposed broadband absorber has potential applications in solar cells, infrared imaging, and thermal emitters.

EDUCATIONAL MATERIALS USING SHIDQ PERSPECTIVE IN THE QUR'AN

This study is a response to the failure of moral education as a result of worldwide breakthroughs in science and technology, which have an effect on the entire human life system, including the world of education. In the realm of education, we should conduct moral development, of which one part, namely the aspect of honesty, has failed. This research seeks to establish the existence of shidq verses in the Qur'an and their relationship to moral education content. The method of research employed is descriptive analysis, with data derived from literature studies. According to the findings of the study, the shidq verses describe the virtues of mah easy or noble moral education material, which include faith, monotheism, piety, istaqamahan, patience, a willingness to sacrifice to seek Allah's pleasure, honesty, perseverance in worship, prayer, promise, and legal discipline. The verses of shidq also emphasize the dangers of mazmumah or despicable moral education materials, namely, including accusations against the Prophet making up the Qur'an, lying or hypocrisy, doubting, shirk, impunity, even to kufr

Challenges and opportunities in using ionic liquids-modified carbon allotropes as emerging anticorrosive nanomaterials

• Ionic Liquids-Modified Carbon Allotropes (ILMCAs) were surveyed as noble anticorrosive materials. • ILMCAs act as nanofillers and are gaining growing attention as they strongly enhance corrosion resistance. • ILMCAs act as much more effective nanofillers than polymer composite nanofillers. • ILMCAs can be regarded as environmentally substitutes for polymer composites. • The challenges and opportunities of ILMCAs as nanofillers are described. Ionic Liquids-Modified Carbon Allotropes (ILMCAs) embody an emerging class of carbon allotropes-based nanocomposite materials. The materials are associated with various salient features that qualify them for many applications. The use of ILMCAs as nanofillers in polymer coating is gaining growing attention as they strongly enhance the corrosion resistance property of polymer coating. Literature studies showed that ILMCAs manifest relatively high anticorrosive properties as compared to their constituting. For example, a study showed the IL, ROG and RGO-IL-based epoxy resin coatings demonstrate the %IE of 51.96%, 78.46% and 95.02%, respectively. In ILMCAs, ILs enhance the adhesion property whereas carbon allotropes avoid the diffusion of electrolytes. ILMCAs act as effective nanofillers than traditional polymer composite nanofillers. The use of ILMCAs can be regarded as eco-friendly substitutes for traditional nanofillers. The present perspective describes the collections and advancements in ILMCAs as nanofillers in polymer coatings.

Corrosion of NiTi stents induced by galvanic interaction with radiopaque materials

Nickel titanium (NiTi) alloys are used as a base material for biomedical devices and implants, such as stents. One limitation associated with NiTi stents is the low radiopacity. Thus, radiopaque markers, made of noble materials, are usually attached to NiTi stents to increase the stent radiopacity, raising concerns regarding galvanic corrosion in body fluid environments. This research aims to assess the galvanic interactions of NiTi alloys and NiTi stent when coupled to radiopaque markers materials in simulated body fluid solution (NaCl 0.9%). Electrochemical measurements, using flat specimens and NiTi stents were carried out. After the tests, scanning electron microscopy (SEM) surface analysis was performed. The results from polarization curves indicate that the NiTi/Platinum (NiTi/Pt) couple is more susceptible to galvanic corrosion than the pairs of NiTi/Palladium (NiTi/Pd) and NiTi/Gold (NiTi/Au). The potential difference of 628 mV presented by the NiTi/Pt couple was the highest among the galvanic couples investigated. Higher values of galvanic potential and galvanic current were also obtained by the pair NiTi/Pt. In direct galvanic short-term measurements with NiTi stent/Pt, no increase in the current density or presence of pits on the NiTi stent surface was observed. However, long-term potentiostatic test, applying 280 mV, which corresponds to the galvanic potential of the NiTi/Pt couple, resulted in current peaks of 1.500 µA and led to severe localized corrosion of NiTi stents, revealing a risk of corrosion induced by coupling Pt markers to NiTi stent.

A comparative study on binary polymer blends comprising rigid planar low-bandgap semiconductor and flexible coil-type insulator

A polymer blend is an essential member of a class of materials analogous to metal alloys, in which two polymers are blended together to create a noble material with different physical properties. Not only the physicochemical properties of each polymer but also their relative interaction and miscibility are a key to eliciting novel materials properties. Here, we investigated the effects of blending a flexible coil-type insulating polymer on the charge transport characteristics of rigid planar semiconducting polymers. To this end, we systematically controlled the blending ratio of the commercial insulating polymer, polystyrene, and one of two different diketopyrrolopyrrole-based donor-acceptor alternating copolymers, and characterized the electrical, microstructural, and morphological properties of the semiconductor–insulator polymer blend films. We found that the electrical properties of the films are strongly correlated with the polymer blend ratio and the resulting films’ vertical segregation and crystalline structures and that hole transport and electron transport alter differently with the polymer backbone structure and blend ratio. These results are expected to be greatly helpful in optimizing the semiconductor–insulator polymer ink formulations for potential use in printed electronics.

Charged matrix stabilized cobalt oxide electrocatalyst with extraordinary oxygen evolution performance at pH 7

Cheap, durable, and efficient oxygen evolution reaction (OER) catalysts applicable in near-neutral electrolytes are highly desired in various energy conversion applications for establishing carbon neutrality. However, it is very challenging for noble metal-free materials to be efficiently operated in such conditions, and the screening of new compounds has reached a bottleneck for this purpose. Herein, we show that significant stability enhancement can be achieved via novel interfacial interactions through rational integration of components, which opens up a new opportunity to meet this challenge. We realized a mixed oxides film of Co3O4 and CoNb2O6 with a unique heterogeneous architecture, where the Co3O4 active site receives strong protection against dissolution from niobate phases via Coulombic interaction. Moreover, the cobalt niobate phase also promotes the overall charge transport, as suggested by the impedance study. As a result, the heterogeneous catalyst exhibits attractive stability and activities in neutral and even weak acidic electrolytes. This work indicates that the screening criteria of novel ternary oxides OER catalysts should not be limited to the intrinsic property of new phases, and that controlled phase separation can be a convenient tool and a new paradigm for future works.

Design of Ag–Ga–S2-xSex-based eco-friendly core/shell quantum dots for narrow full-width at half-maximum using noble ZnGa2S4 shell material

Design of Ag–Ga–S2-xSex-based eco-friendly core/shell quantum dots for narrow full-width at half-maximum using noble ZnGa2S4 shell material

Evolution of Surface Oxides of UNS S13800 during Cathodic Polarization in Chloride Solutions

Solutions arising from atmospheric processes can have varying chloride concentrations, often higher than seawater as salt deposits accumulate in thin layer electrolytes. Understanding the corrosion behavior of stainless-steel fastener components is important to predicting its behavior in a galvanic couple with less noble materials. Here we have focused on the cathodic kinetics of UNS S13800 stainless steel over a range of chloride concentration electrolytes. The different oxides formed under these varying conditions are studied using surface analytical techniques. This information is then used to inform a model for fitting of the potentiodynamic polarization curves. The evolving composition of the surface oxide affects the polarization curve in the activation region of the oxygen reduction reaction. This additional cathodic current is accounted for in the model and the different reaction components of the polarization curve are extracted and analyzed.AcknowledgmentsThe U.S. Naval Research Laboratory sponsored this project as part of their base program. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research, the U.S. Navy, the Department of Defense, or the U.S. government

Ni3Fe nanoparticles encapsulated by N-doped carbon derived from MOFs for oxygen evolution reaction

It has been a hot research topic to look for inexpensive alternative oxygen evolution reaction (OER) catalysts to replace noble metal-based materials due to their scarcity. Transition metals are ideal candidates because of their high abundance, impressive activities, and easy accessibility. However, a facile method leading to improved performance and stability is still needed. Herein, a highly efficient carbon-encapsulated bimetal catalyst derived from Ni-based metal-organic-frameworks (MOF) was successfully prepared through the low-temperature (350 ℃) pyrolysis of Prussian blue analogue (PBA) precursors under H 2 /Ar atmosphere. Cube-structured PBA as template and precursor，parameters during the pyrolysis process including temperature and calcination atmosphere can be tuned to control the structure and properties of the catalysts. Benefiting from the porous three-dimensional (3D) cubic structure and abundant defect-rich amorphous N-doped carbon shell, Ni 3 Fe@NC-350 exhibits excellent OER activity. The as-prepared catalysts exhibited excellent catalytic performance for OER in 1.0 M KOH with an overpotential of 237 mV to achieve 10 mA cm −2 . More importantly, the presented catalyst has an extremely good durability. • A simple low-temperature annealing method was developed to produce alloy encapsulated with N-doping carbon. • The NiFe PBA was employed as nitrogen and carbon source. • The increased activity of OER is due to the synergy of Ni 3 Fe alloy and N-doped carbon layer. • Theoretical calculations revealed that the synergistic effect of NiFe alloy nanoparticles and N-doped carbon layer.

Highly dispersed CoPx nanoparticles supported on carbon cloth for the enhanced catalytic performance of methanol electro-oxidation

Direct methanol fuel cell (DMFC) is a potential commercial fuel cell technology that is presently hindered by the expensive noble metal materials of the anode. Developing a method to obtain a uniformly dispersed metal phosphide catalyst with narrow size distribution is still a challenge. In this work, cobalt oxide was deposited on carbon cloth (CC) through atomic layer deposition (ALD), then cobalt phosphide was obtained after the phosphorization process. By changing the number of ALD-based ozone pulses (ALD-O3) for CC, the nucleation and growth modes of cobalt oxide (ALD-CoOx) on the CC were regulated, and CoPx nanoparticles with small particle size and uniform distribution were obtained. The optimized CoPx-based catalyst with 40 cycles of ALD-O3 treatment (CoPx/40-CC) exhibits excellent activity (153 mA/cm2) toward methanol electrocatalytic oxidation reaction in the alkaline solution, which is higher than the catalyst prepared by impregnation (Imp-CoPx/CC), although the CoPx loading of CoPx/40-CC is lower than that of Imp-CoPx/CC. The results indicate that the enhanced activity benefits from the small particle size and the uniform CoPx distribution, which promote the electron-transfer and mass transport kinetics of the methanol electro-oxidation process.

Strategies to improve the catalytic activity and stability of bioinspired Cu molecular catalysts for the ORR

The oxygen reduction reaction (ORR) is essential for energy conversion devices such as fuel cells and metal-air batteries. The use of expensive and scarce noble metal materials to catalyze the ORR is a limitation for the massification of these energy conversion technologies. Copper molecular catalysts that mimic the active sites of metalloenzymes such as laccase are under continuous development. In this minireview, we present the strategies to increase the activity and stability of the copper catalysts for the ORR. The flexibility, lability, and electronic character of the ligands are crucial to promote the ORR. In addition, the use of polymers as backbone for multicopper catalysts and the synthesis of copper carbon-based pyrolyzed catalysts present remarkable results with promissory applications. • The rational design of bioinspired Cu-catalysts should focus on the ligand structure. • Ligands' flexibility and lability in Cu-catalysts are crucial to promoting the ORR. • Multicopper catalysts present higher ORR catalytic activity than mononuclear ones. • The stability of multicopper catalysts should be improved. • Multicopper polymeric or pyrolyzed catalysts show remarkable ORR catalytic activity.

Molecular Thermodynamics for the Redox Reaction of Sodium Tetrachloroaurate, NaAuCl4 (Noble Material) with Giemsa Stain (GS) Dye in HNO3 Solution Using Cyclic Voltammetry

Molecular Thermodynamics for the Redox Reaction of Sodium Tetrachloroaurate, NaAuCl4 (Noble Material) with Giemsa Stain (GS) Dye in HNO3 Solution Using Cyclic Voltammetry