Traditional Precious Metal Research Articles

The relationship between silver prices and consumer price index: Evidence on China market

This study examines the relationship between Chinese silver prices and inflation to help investors predict inflation in China and hedge risks during inflationary periods. This article constructs a regression model using the least squares method with silver price as the independent variable, consumer price index (CPI) as the dependent variable, and gold price as the control variable. According to the regression model, the research results indicate that in China, inflation risk cannot be predicted by the price of silver, and even investors cannot hedge their risk with silver during inflation periods. On the contrary, as a traditional precious metal, gold can predict inflation and provide hedging during this period. Based on these findings, this article suggests that Chinese investors should pay attention to the hedging differences between precious metals and make correct investment strategies based on the impact of silver and gold prices on inflation to cope with China’s growing inflation risk.

Effective oxygen evolution of NCF@CoNiO2 with one-dimensional core-shell structure synthesized by induced effect of polymer nanofibers

The non-noble bimetallic oxides have recently received more and more attention in electrocatalytic oxygen evolution reaction (OER) because of their potential to replace traditional precious metal catalysts, but the low activity and stability limit their wide application. Herein, the bimetallic oxide CoNiO2 layers are decorated on the nitrogen-doped carbon nanofibers (NCF) through in situ grown of Ni(Co) bimetal organic frameworks (Ni(Co)-MOFs) on polyacrylonitrile nanofibers and subsequent pyrolysis process, so that a new NCF@CoNiO2 electrocatalyst with one-dimensional (1D) core-shell structure is synthesized by structural induced effect of polyacrylonitrile nanofibers. Importantly, the unique interconnected network formed in the 1D NCF@CoNiO2 electrocatalyst effectively improves electron mobility and mass transport capacity, thus exhibiting the glorious OER activity and long-term stability in alkaline solutions. As a result, the optimal NCF@CoNiO2-7 electrocatalyst requires an overpotential of 518 mV for OER at the current density of 100 mA cm−2, which is obvious lower than that of RuO2 (633 mV) and CoNiO2/C-7 as a contrast sample (569 mV), respectively. This work opens up a new path for structural control of 1D bimetallic oxides to improve OER activity and stability.

Non-precious metal high-entropy electrocatalysts (Al0.5NiCoCr-X0.5) for OER application

The high entropy alloy electrocatalysts demonstrate exceptional efficiency in the production of hydrogen through water electrolysis. Consequently, the development of durable and economically efficient electrocatalysts has become an urgent objective to accomplish. In order to achieve this goal, a bulk non-precious metal high-entropy alloy, Al0.5NiCoCr-X0.5 (Mo, Mn, Cu, V, Fe), was synthesized and characterized in this study through physical phase analysis and electrochemical property test. To explore the reasons for the influence of the five added elements on the catalytic performance of high entropy alloys in this system and to find the OER electrocatalyst with the best catalytic performance. Electrochemical performance tests were performed in 1 M KOH electrolyte. At a current density of 10 mA·cm−2, the overpotential of the high-entropy alloy catalyst Al0.5NiCoCrMo0.5 was lower than that of the high-entropy alloy with the addition of the other four elements respectively, which was only 327 mV, and lower than that of the conventional noble metal catalyst RuO2, which had an overpotential of 342 mV. This is attributed to the addition of Mo element, which makes Al0.5NiCoCr produce a large number of HCP phases on top of the original FCC phase and a very small number of BCC phases, which is more conducive to the generation of active sites on the surface of the catalysts, and thus improves the OER activity, and the stability can be maintained for at least 20 hours. Therefore, Al0.5NiCoCrMo0.5 high-entropy alloy catalysts can be used in industrial hydrogen production instead of the traditional precious metal catalysts, and it has a rather broad application prospect, and at the same time, it lays a solid foundation for the application of transition metals in catalysts.

Co, N, and P co-doped few-layer graphene derived from cobalt phthalocyanine-based covalent organic polymers as bifunctional electrocatalysts for overall water splitting

Water electrolysis is considered to be one of the most promising approaches for developing sustainable energy technologies, however, the high cost and lack of stability of traditional precious metal electrocatalysts have hindered the development of the field of water electrolysis. Covalent organic polymers have greater potential for the preparation of low-cost electrocatalysts with high efficiency and long-term stability due to their low cost, controllable chemical composition, and rich pore structure. Cobalt phthalocyanine-based covalent organic polymers were loaded onto few-layer graphene by a hydrothermal method and then pyrolyzed to produce Co, N, and P co-doped few-layer graphene (Co–N/P-FG-700). Co–N/P-FG-700 demonstrates superior performance for oxygen evolution reaction (OER) due to the synergistic effect of abundant active sites and conductive carriers, with an overpotential of 358 mV at a current density of 10 mA cm−2 and 90% of the current density after 50,000 s of stability testing. Co–N/P-FG-700 exhibits excellent results for hydrogen evolution reaction (HER) with an overpotential of −275 mV at a current density of −10 mA cm−2 and a current density retention of 93% after a 50,000 s stability test. This study provides a rational pathway for the design of low-cost, high-performance, stable bifunctional OER/HER electrocatalysts.

Defective Carbon Derived Using a Dissolution-Recrystallization Strategy for Oxygen Reduction Electrocatalysis.

Dopant-free defective carbon electrocatalysts have been considered as promising alternatives to traditional precious metal electrocatalysts recently. Compared with precious metal catalysts and transition-metal catalysts, since there are no metals doped, electrochemical devices assembled with dopant-free defective carbons are free from environmental pollution and subsequent recovery problems. In order to obtain abundant carbon defects with high-intrinsic catalytic activity, the synthesis of dopant-free defective carbons requires complex and harsh preparation conditions. Therefore, the construction of active defects with efficient utilization, especially through a simple process, is still a great challenge for the development of dopant-free defective carbon electrocatalysts. Herein, dissolution-recrystallization strategy was employed to design Zn-MOF-74 precursors for the synthesis of dopant-free defective carbons, realizing the synchronous manipulation of high ratio of carbon defects and highly exposed mass transfer channels. One-dimensional porous defective carbon nanorods (d-CNRs), which exhibited excellent oxygen reduction reaction (ORR), electrocatalytic activity, and molecular selectivity, were synthesized by directly carbonizing rodlike Zn-MOF-74 precursors. Attributed to the dissolution-recrystallization strategy, with the activation of in situ-formed ZnO, the synthesized d-CNRs exhibited unique pore-crack nested porous structures, which carried abundant defects as activity sites for ORR and showed a surprisingly high specific surface area of 2459 m2/g with a high ratio of mesopores. d-CNRs also showed promising applications in Zn-air batteries with a stable long-term discharge of no obvious voltage drop after 60 h. The dissolution-recrystallization strategy provided a simple controllable pathway for the efficient construction of dopant-free defective carbon electrocatalysts.

Visible Light-Mediated Quantum Dot Photocatalysis Enables Olefination Reactions at Room Temperature

The ability of quantum dots (QDs) to photocatalyze organic reactions is gaining attention because of their distinct light harvesting properties over traditional precious metal- and small molecule-based catalysts. However, establishing the potency of QD photocatalysts in diverse and useful organic transformations, as well as deciphering the charge transfer mechanism, is essential to cement their place as an efficient photocatalyst in synthetic chemistry. Here, we report the use of QDs in efficiently catalyzing a series of olefination reactions under visible-light irradiation at room temperature (90% yield). Spectroscopic and electrochemical studies reveal intriguing insights on the charge transfer mechanism involved in QD-photocatalyzed olefination. Interestingly, the dual role of triphenylphosphine─as a surface passivating agent and nucleophile─turned out to be decisive in directing the charge transfer process from the QD to the reactant. Benzyl triphenylphosphonium bromide salt was accepting the electrons from the photoexcited QDs, thereby initiating the catalytic olefination reaction. QD-photocatalyzed olefination was demonstrated with formaldehyde as well, resulting in the formation of industrially relevant terminal alkene, namely styrene. Moreover, the environmentally friendly indium phosphide (InP) QD also photocatalyzed the olefination reaction under mild reaction conditions, which proves the practical suitability of our study. This work presents an attractive and efficient way to introduce double bonds in organic molecules using QDs and visible light at room temperature.

Interfacial Coordinational Bond Triggered Photoreduction Membrane for Continuous Light-Driven Precious Metals Recovery.

Chemical/electric energy-driven processes dominate the traditional precious metal (PM) recovery market. The renewable energy-driven selective PM recycling approach crucial for carbon neutrality is under exploration. Herein, via an interfacial structure engineering approach, coordinational-active pyridine groups are covalently integrated onto the photoactive semiconductor SnS2 surface to construct Py-SnS2. Triggered by the preferred coordinational binding force between PMs and pyridine groups, together with the photoreduction capability of SnS2, Py-SnS2 shows significantly enhanced selective PM-capturing performance toward Au3+, Pd4+, and Pt4+ with recycling capacity up to 1769.84, 1103.72, and 617.61 mg/g for Au3+, Pd4+, and Pt4+, respectively. Further integrating the Py-SnS2 membrane into a homemade light-driven flow cell, 96.3% recovery efficiency was achieved for continuous Au recycling from a computer processing unit (CPU) leachate. This study reported a novel strategy to fabricate coordinational bonds triggered photoreductive membranes for continuous PM recovery, which could be expanded to other photocatalysts for broad environmental applications.

Cu/CeO2 and Cu/Gd-Substituted CeO2 Aerogels as Active, Selective, and Stable COPROX Catalysts

Purifying hydrogen feedstocks necessitates preferential oxidation of carbon monoxide (COPROX), but traditional precious metal catalysts are poorly selective, while transition metal catalysts suffer from insufficient activity and stability. We report that Cu nanoparticles supported on CeO2 or Gd(III)-substituted CeO2 (GCO) aerogels deliver a rare combination of high activity, selectivity, and stability for COPROX. The reducing oxide disperses Cu and stabilizes its more active low-valent state. Aerogel-supported Cu oxidizes CO at low temperature but requires higher temperatures to oxidize H2 and, therefore, shows wide temperature ranges with >95% CO conversion and >95% selectivity vs H2. This performance is maintained for >16 h of continuous operation in dry or humidified reaction streams. The Cu/GCO aerogel is less active than Cu/CeO2 under dry feedstreams but experiences less loss of activity under humid conditions because the higher surface area of the former distributes surface-adsorbed water along the network and reacts it at oxygen vacancies. Aerogel-based architected catalysts offer an effective design route to achieve high and stable catalytic activity under industrially relevant conditions.

Malay Traditional Motifs Character in Jewellery Design

This study determines the traditional Malay motifs design that was discovered in the jewellery artefact collections from the National Museum Kuala Lumpur. The visit and support with the observation of the jewellery collection assisted in the process of digital compilation. Then the categorisation of types of jewellery was then divided into three categories of traditional accessories. The identification of motifs clearly showed how the formation of flora, fauna, abstract, cosmos and geometric characters was used and developed. This compilation of this study significantly sustains the tradition of this unique traditional precious metal heritage towards the contemporary design sources for future.

Study on the anode stability of polyaniline with its pyrolysis products as electroactive components and the experimental study of cobalt electrowinning in chloride system

In the field of nonferrous metal extraction and wastewater treatment, novel electrode materials have been known as the “heart” of the whole electrochemical innovation process. It can be seen that they play a key innovative role in this process. In this study, the catalytic activity of the novel polyaniline composite electrode material prepared in the laboratory will be comprehensively evaluated, its stability and failure mechanism will be appraised, the mechanism of electrode failure will be described, the ways to improve electrode performance will be put forward, and the superior working performance of the Ti/SnO2-Sb2O5-PANI (9%) electrode material different from the traditional precious metal electrode material will be deeply explored. The research results mainly show that Ti/SnO 2-Sb2O5-PANI (9%) electrode has good stability and can run stably for 186 h when used as anode in electrolysis experiment, while Ti/SnO 2-Sb2O5 electrode has stable operation time of only 114 h. Its failure is mainly caused by the dissolution and falling off of surface coating. In addition, it shows high electrocatalytic activity, low cell voltage of 2.258 V and high current efficiency of 85 ∼ 96% during cobalt electrodeposition experiment.

Efficient hydrothermal growth of high-performance MoS2/pyramid-Si photocathodes by surface hydrophilicity engineering

Compared with traditional precious metal catalysts, MoS2 is regarded as the promising hydrogen evolution reaction catalyst for Si photocathodes, because of its higher photochemical stability and lower hydrogen adsorption free energy. However, the layers of MoS2 are connected by van der Waals force, and the interaction force between the layers of MoS2 and Si is weak. Therefore, the homogeneous MoS2 nanosheets directly synthesized on Si by the hydrothermal method remain challenging. Herein, we report a facile strategy for the fast and efficient growth of vertically standing MoS2 on pyramid Si via surface hydrophilicity tailoring by inserting a thin TiO2 layer. Thanks to the improved light trapping and catalytic kinetics, the optimal MoS2/TiO2/Si shows a short-circuit photocurrent density of 9.79 mA/cm2 and an onset potential of 0.31 V vs reversible hydrogen electrode under 100 mW/cm2 Xe-lamp illumination. By comparing with different oxide buffer layers, surface hydrophilicity is found to be essential for promoting the homogenous nucleation and growth of vertically standing MoS2 by the hydrothermal method. These results not only provide valuable insight into the growth kinetics of transition metal chalcogenides in aqueous solution but also deliver an efficient route for assembling noble-metal free catalysts on silicon-based photoelectrodes.

A dandelion-like amorphous composite catalyst with outstanding performance for sodium borohydride hydrogen generation

Sodium borohydride has attracted much attention because of its high hydrogen density, low hydrolysis temperature and safety. However, most of the current catalysts are expensive and their performances are easily attenuated. Therefore, the development of new catalysts with excellent performances and low cost is the key to its application. In this work, a novel dandelion-like CoMoNi–B/ZIF-67 catalyst with excellent performance was prepared by chemical reduction at room temperature, wherein the CoMoNi–B amorphous alloy was evenly wrapped on the ZIF-67 carrier through liquid phase reduction to form a dandelion-like composite catalyst, of which the “flower bud” ZIF-67 carrier is about 500 nm, and the “crown” flocculent amorphous alloy is about 400 nm. The as-synthesized CoMoNi–B/ZIF-67 has a dandelion-like structure, uniform distribution, large specific surface area, and exhibits an excellent catalytic activity with an apparent activation energy of 35.01 kJ/mol calculated by the Arrhenius equation. Its catalytic hydrolysis rate for sodium borohydride reaches up to 6277 (mL H2 min/g Co and Ni) at 25 °C. Compared with traditional precious metal catalysts, this novel dandelion-like CoMoNi–B/ZIF-67 catalyst has simple preparation, low cost, and easy availability of raw materials, has great potential application for hydrogen generation in NaBH4 hydrolysis.

Chemically synthesized hydrogen fuel from reaction of methylcyclohexane over nanoporous heterogeneous catalysts

ABSTRACT Nanoporous oxides have been prepared, as hosts for the encapsulation of metal nanoparticles, and tested for the catalytic decomposition of methylcyclohexane (MCH) to produce hydrogen gas as a potential fuel source. The aim of the work is to test a range of mixed metal nanoparticle catalysts in the MCH to hydrogen reaction. The work investigates the use of a range of inexpensive metals in conjunction with traditional precious metal e.g. Pt. The objectives of work are prepared nanoporous oxides, comprising MCM- and SBA-types using established methods. Encapsulated metal nanoparticles within the pores of nanoporous oxide. Catalysts have been characterized fully to confirm porosity, surface area, and nanoparticle dispersion. The activity of catalytic of the various nanoporous materials was determined in the MCH to hydrogen reaction, and kinetic models developed from the associated experimental findings.

Photo-responsive metal/semiconductor hybrid nanostructure: A promising electrocatalyst for solar light enhanced fuel cell reaction

Direct alcohol fuel cells (DAFCs) have received wide attention as a new type of clean energy device because of their high energy conversion efficiency, portability, non-toxicity and pollution-free. Anode catalysts are the key factors affecting the performance of DAFCs. Recently studies show that using the optical activity of semiconductor materials as the carriers of traditional precious metal electrocatalysts, under the illumination of light sources, can greatly improve the electrocatalytic activity and stability of electrodes. In this review, the research progress of photo-responsive metal/semiconductor hybrids as the electrocatalysts for DAFCs in recent years is summarized, including: (1) Mechanism and advantages of photo-assistant electrochemical alcohol oxidation reaction, (2) metal/semiconductor electrocatalyst for the different type of fuel cell reactions, (3) different kind of metals in photo-responsive metal/semiconductor hybrid nanostructure, (4) the personal prospects of the photo-responsive metal/semiconductor electrode for future application in DAFCs.

One step synthesis of 2,5-furandicarboxylic acid from fructose catalyzed by Ce modified Ru/HAP

A series of Ce-modified Ru/HAP catalysts with different loadings were prepared by impregnation method, which were applied to the one-step preparation of 2,5-furandicarboxylic acid with fructose. The catalysts were characterized by XRD, TEM, NH3-TPD and XPS. The results showed that Ce was highly dispersed on the HAP, and the addition of Ce affected little on the structure of HAP. Ce mainly exists in the form of Ce3+ and Ce4+. The presence of the Ce3+ makes a large amount of oxygen holes on the surface of the catalyst, and the electron transfer between Ce3+ and Ce4+ is conducive to the formation of oxygen holes, improves the oxygen storage capacity and the surface catalytic activity. The catalyst is rich in weak acid sites, which inhibits the side reactions. Among the catalysts evaluated, the sample of Ce (8%, mass ratio) -Ru/HAP showed satisfied performance with the 2,5-FDCA yield of 34.2% at 160°C for 4 h reaction under a pressure of 2 MPa and a catalyst dosage of 0.1 g. Therefore, the introduction of Ce has greatly improved the catalytic activity of traditional precious metal composite catalysts, and also provided new ideas for the one-step preparation of fructose 2,5-FDCA.

A Comparison Between Solders & Transient Liquid Phase Sintered Interconnects in High Temperature Multilayer Ceramic Capacitors

There is a long-established market for high temperature multilayer ceramic capacitors (MLCCs) that operate at 150°C and higher in downhole oil and gas exploration, and military and aerospace applications. To maximize the capacitance density and achieve a high degree of mechanical robustness, stacks and leaded form factors have been used with high melting point–Pb-containing solders as the preferred interconnects. However, Pb-containing solders are limited to temperatures below 300°C and are banned from many commercial and automotive applications with further legislation limiting their use planned in the future. Common Pb-free solders such as SAC 305 or SnSb alloys are in widespread use, but their performance at prolonged exposures at 200°C is limited. Exposures to high reflow temperatures during assembly, especially successive reflow operations, can also compromise interconnect integrity. Higher temperature gold-containing solders are widely available, but these are cost-prohibitive and so are not viable for emerging high temperature electronics including higher volume, price-sensitive automotive and power markets. The development of more energy-efficient power converters and inverters based on wide bandgap semiconductors is driving the adoption of higher temperature electronics in these markets because these operate at higher junction temperatures than traditional silicon. This has led to the development of nonsolder interconnects based on sintered silver, nanometal sintering, and transient liquid phase sintering (TLPS) technologies capable of higher temperature performance than common solder-based interconnects. The availability of discrete components, such as capacitors, that can operate under these conditions is a key barrier to the development and adoption of high temperature electronics. In this article, the key property differences between solders and TLPS interconnect technologies are compared in detail for MLCC interconnects. The development of a new range of nickel base metal electrode C0G MLCC stacks rated for 200°C is described and performance compared with traditional precious metal electrode stacks. Thermal cycling performance to 200°C of BME X7R stacks made with 10Sn/88Pb/2Ag solders are compared with similar stacks made with TLPS interconnects of CuSn and InAg. The development of leadless stacks, a new bulk capacitance form factor enabled by TLPS technology, is described and their properties compared with traditional stacks.

A study on the catalytic hydrogenation of N-ethylcarbazole on the mesoporous Pd/MoO3 catalyst

Mesoporous MoO3 shows an apparent activity in the catalytic hydrogenation of N-ethylcarbazole (NEC), where a significant amount of tetrahydro-N-ethylcarbazole (4H-NEC) and perhydro-N-ethylcarbazole (PNEC) are detected with the hydrogen uptake of 0.97 wt% after 6 h when the temperature rises to 220 °C. 0.5 wt% Pd/MoO3 catalyst shows a superior catalytic efficiency than the traditional precious metal catalysts 0.5 wt% Ru/Al2O3 and 0.5 wt% Pd/Al2O3, especially in the conversion of Octahydro-N-ethylcarbazole (8H-NEC) to PNEC. The hydrogenation mechanism of MoO3 is completely different from the traditional precious metal catalysts. With the presence of a small amount of Pd, the breaking of HH bond is greatly accelerated, result in the promotion of hydrogen spillover rate and the increase of the concentration of hydrogen molybdenum bronze HxMoO3, which improves the catalytic efficiency of the MoO3 catalyst. Rise the temperature also helps increasing the concentration of H in HxMoO3.

A Comparison Between Solders & Transient Liquid Phase Sintered Interconnects in High Temperature Multi-Layer Ceramic Capacitors

Abstract There is a long-established market for high temperature multi-layer ceramic capacitors (MLCC) that operate at 150°C and higher in down-hole oil & gas exploration, military and aerospace applications. To maximize the capacitance density and achieve a high degree of mechanical robustness, stacks and leaded form factors have been used with High Melting Point (HMP) Pb-containing solders as the preferred interconnects. However, Pb-containing solders are limited to temperatures below 300°C and are banned from many commercial and automotive applications with further legislation limiting their use planned in the future. Common Pb-free solders such as SAC 305 or SnSb alloys are in widespread use but their performance at prolonged exposures at 200°C is limited. Exposures to high reflow temperatures during assembly, especially successive reflow operations, can also compromise interconnect integrity. Higher temperature gold-containing solders are widely available but these are cost prohibitive and so are not viable for emerging high temperature electronics including higher volume, price sensitive Automotive and Power markets. The development of more energy efficient power converters and inverters based on Wide Band Gap (WBG) semiconductors is driving the adoption of higher temperature electronics in these markets since these operate at higher junction temperatures than traditional silicon. This has led to the development of non-solder interconnects based on sintered silver, nano-metal sintering and transient liquid phase sintering (TLPS) technologies capable of higher temperature performance than common solder based interconnects. The availability of discrete components, such as capacitors, that can operate under these conditions is a key barrier to the development and adoption of high temperature electronics. In this paper the key property differences between solders and TLPS interconnect technologies are compared in detail for MLCC interconnects. The development of a new range of nickel Base Metal Electrode C0G MLCC stacks rated for 200°C is described and performance compared to traditional Precious Metal Electrode (PME) stacks. Thermal cycling performance to 200°C of BME X7R stacks made with 10Sn/88Pb/2Ag solders are compared to similar stacks made with TLPS interconnects of Cu-Sn and In-Ag. The development of leadless stacks, a new bulk capacitance form factor enabled by TLPS technology, is described and their properties compared to traditional stacks.

Abundant Metals Give Precious Hydrogenation Performance

Iron- or cobalt-based catalysts have outperformed traditional precious metal catalysts in several hydrogenation reactions. [Also see Reports by Jagadeesh et al. , Friedfeld et al. , and Zuo et al. ]