Clean Metal Research Articles

Metallic Electro-optic Effect in Gapped Bilayer Graphene.

Electro-optic (EO) modulation is a critical device action in photonics. Recently, the non-Drude dynamics induced by the Berry curvature dipole (BCD) in metals have attracted attention as a potential candidate for terahertz EO modulation. However, such BCD-induced EO effects can be challenging to realize, often requiring flat bands and complex materials such as a strained magic-angle twisted bilayer graphene on hexagonal boron nitride. Here, we argue that metallic EO can be achieved with a much simpler material, gapped bilayer graphene, with EO coefficients comparable to that in flat-band materials in the terahertz range. In particular, we find metallic EO can be realized without a Berry curvature dipole; we identify skew-scattering and a "snap" (third-order derivative of velocity) can readily produce pronounced Pockels and Kerr EO effects in clean metals. These yield nonreciprocal and field-activated birefringence and field-induced modulations to transmission and reflection, essential components for terahertz EO modulators.

Ni Nanoparticles in Functionalized Ionic Liquids for Chemoselective Hydrogenation Catalysis

The decomposition of organometallic Ni0 complexes with stabilizing agents - named the organometallic approach - is an attractive method to obtain size-controlled Ni nanoparticles (NPs) in solution. The method allows fine control of the NPs growth, while offering a clean metal surface due to the absence of byproducts formed from the precursor complex. Moreover, the nature of the stabilizer can be tuned to affect the catalytic properties of the Ni NPs [1].Ionic liquids (ILs) can function as both stabilizers and dispersion media for the synthesis of small and narrow-sized Ni NPs by the organometallic approach under mild conditions [2]. Such systems can also benefit from the use of functionalized ILs (FILs) that can interact with the metallic surface and create ligand effects during catalysis [3]. Controlled oxidation forming Ni-NiO NPs is another approach to modify the catalytic reactivity, as previously shown for solid NiO catalysts [4].In this work, well-defined Ni NPs were synthesized in different ILs (Ni/ILs) and exploited as catalysts for the chemoselective reduction of 2-cyclohexen-1-one, as a representative of the group of α,β-unsaturated carbonyl compounds with industrial relevance [5]. Interestingly, the Ni/ILs systems were found to be efficient catalysts for selective hydrogenation of the substrate to cyclohexanone using hydrogen gas with performance dependence on the applied ILs whereas the oxidized counterparts (Ni-NiO/ILs) were active and selective for catalytic transfer hydrogenation to 2-cyclohexen-1-ol with 2-propanol as H-source and solvent, both under mild reaction conditions (Figure 1).The work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 860322.[1] C. Amiens, D. Ciuculescu-Pradines, K. Philippot, Coord. Chem. Rev. 2016, 308, 409.[2] M.H.G. Prechtl, P.S. Campbell, J.D. Scholten, G.B. Fraser, G. Machado, C.C. Santini, J. Dupont, Y. Chauvin, Nanoscale 2010, 2, 2601.[3] D. Krishnan, L. Schill, M.R. Axet, K. Philippot, A. Riisager, Nanomater. 2023, 13, 1459.[4] J. He, M.R. Nielsen, T.W. Hansen, S. Yang, A. Riisager, Catal. Sci. Technol. 2019, 9, 1289.[5] D. Krishnan, L. Schill, M.R. Axet, K. Philippot, A. Riisager, ChemCatChem 2024, 16, e202301441. Figure 1

Quantile time-frequency connectedness and portfolio diversification: A study of clean energy and metal markets

Severe climate change has accelerated the shift towards renewable energy sources. In this study, we explore the spillover effects and portfolio diversification between clean energy and metal markets, using the quantile time-frequency analysis. Our analysis incorporates the quantile frequency connectedness framework, MODWT method, and DCC approach. The findings reveal the following key insights: (i) There exists significant spillover between clean energy and metal markets, characterized by dynamic patterns. Short-term spillover effects are particularly pronounced, contributing the most to overall connectivity. Interestingly, the conditional median-based measure underestimates spillover levels in extreme market conditions.(ii) Clean energy and base metal markets emerge as the primary net transmitters, while other strategic metal markets mainly act as net receivers.(iii) Optimal portfolio allocation for investors in clean energy metal portfolios suggests a higher proportion of wind energy assets compared to clean and solar energy assets. It is also recommended that investors adjust their portfolio structure and hedge positions according to market conditions. These findings carry crucial implications for investors and regulators in shaping their investment strategies and policies in response to the changing dynamics of clean energy and metal markets.

Design of honeycomb-imitated composite hydrophobic aerogel and applications for multifunctional water cleaning

It is a huge challenge to integrate comprehensive properties in photothermal materials for multifunctional application in various aspects of water cleaning and purification. In this study, inspired by honeycombs, a polysiloxane/polyimide/carbon composite hydrophobic aerogel (Bio-SPC aerogel) is fabricated using a blending-crosslinking-directional freezing-gradient heating method, and exhibits reasonable structure and component regulation for multiple applications such as oil–water separation, photothermal crude absorption and water evaporation. Primary vertical porous channels and the secondary structure of fibrous carbon on the aerogel’s cell walls reduce light reflection and provide a large light absorption area, respectively, promoting photothermal conversion properties. Another secondary structure of micro-nano pores enhances heat preservation. Through convenient pre-processing and directional freeze-drying, methyltrimethoxysilane is hydrolysis-condensed and bound to the structure skeleton formed using polyimide precursor and bacterial cellulose biomass, coating on the surface to mimic beeswax’s enhanced hydrophobicity and mechanical strength. The aerogel exhibits a mechanical strength of 32 kPa at 80 % strain and good structural stability over 500 cycles, as well as efficient light-to-heat conversion with a fast temperature increase (reaching 75.3℃ in 30 s) and a maximum stable temperature of nearly 100℃. Its solvent absorption capacity is 74.2 g/g and it has a flux retention rate of 71 % after 10 cycles of oil–water separation. Under sunlight irradiation, the aerogel absorbs crude oil more quickly during cleanup. The assembled aerogel evaporator has an average evaporation rate 4.2 times that of bulk water and 96.6 % efficiency. The evaporation performance is stable in high-concentration saline water and long-term cycles, with a maximum rate of 2.675 kg m-2 h−1 outdoors. This novel honeycomb-inspired composite aerogel shows promise for multifunctional applications, including oily water cleaning, crude cleanup, seawater desalination, and heavy metal or organic dye removal from polluted water.

Climate policy uncertainty, clean energy and energy metals: A quantile time-frequency spillover study

Climate change mitigation has become a global imperative, making the development of clean energy very important. This paper explores the risk contagion effects among climate policy uncertainty (CPU), clean energy, and energy metals from the quantile time-frequency spillover perspective. The results show that: (1) The spillover effects among climate policy uncertainty, clean energy, and energy metals are nonlinear across the entire conditional distribution, showing a “V” shape, with the right-tailed risk contagion effect being more significant. (2) The risk contagion effect is abruptly enhanced by external extreme event shocks, with stronger market connectivity in the low-frequency band compared to the high-frequency band. Short-term spillover effects dominate cross-market risk contagion in the upper quantile, while long-term spillover effects dominate the lower quantile. (3) The spillover network is characterized by abrupt structural changes. That is, clean energy is a source of risk contagion at lower quantiles, while energy metals are a source of risk contagion at upper quantiles. (4) The CPU acts as an important node in the cross-market risk contagion path. Driven by CPU, the upper quantile and the long-term risk transmission is along “energy metal-clean energy” path, while the lower quantile and the short-term risk transmission is along “clean energy-energy metal” path.

The effect of geopolitical risk on the clean energy metals’ prices: the evidence of BRICS countries

ABSTRACT This study examines the effect of geopolitical risk on clean energy metal prices for Brazil, Russia, India, China and South Africa (BRICS) countries. Aluminum, cobalt, copper, nickel and zinc have been used as clean energy metals. The research period was determined as January 1990 to August 2021. Hatemi-J and Roca (2014) asymmetric causality test was used as the research method. According to the results, there is no causality between geopolitical risk of South Africa and cobalt prices for different cases. However, in general, there is causality between other clean energy metal prices and geopolitical risk in BRICS countries. Accordingly, the geopolitical risks of the BRICS countries both affect and are affected by these metal prices. This result suggests that changes in geopolitical risk of BRICS countries can provide useful information in explaining changes in clean energy metal prices. Likewise, changes in clean energy metal prices provide useful information in explaining the changes in geopolitical risk of BRICS countries. Therefore, policy makers need to develop new policies and strategies that can protect BRICS countries from clean energy metal price fluctuations in order to effectively use their renewable energy resources in their economic development.

LEED-IV analyses of tellurium adsorbate structures on iridium and gold surfaces

The determination of the configuration of atomic adsorbates on clean metal surfaces has been a key issue in surface science 60 years ago and still is today. We demonstrate that despite the prevalence of combined scanning tunneling microscopy and density functional theory studies of adsorbate systems the pitfalls are plentiful calling for accurate, reliable structure analyses that can be delivered by diffraction methods. We analyze and compare the ordered phases of Te on Ir(111), Ir(100), and Au(100) demonstrating the accuracy, the in-depth information and physical insight that can nowadays be obtained by quantitative low-energy electron diffraction structural analyses.

Insight into clean energy market’s role in the connectedness between joint-consumption metals

The characteristic of joint consumption creates complex linkage between metal markets, which helps provide new insights into the energy-metal nexus relationship. To this end, this paper analyzes the price spillover effects between clean energy metals with joint consumption properties and further captures clean energy market's role in this dynamic connectedness. The results show that: (1) There are significant spillover effects within the clean energy metal markets, mainly dominant by short-term factors. The price fluctuation risk in the wind energy metal markets is more easily transmitted than the solar energy metal markets. (2) Copper and Tellurium markets are the main sources of risk in the spillover network of solar energy metal markets, while Copper and Aluminum act as the centers of risk transmission in the spillover network of wind energy metal markets. (3) Clean energy markets significantly impact the spillovers of metal markets, and exhibit non-linear movements, altering the spillover roles of some metal markets in the spillover network. Our findings reveal the system-wide price fluctuation patterns in clean energy metal markets, helping provide targeted recommendations in the risk management of energy-metal nexus system.

Analyzing Crisis Dynamics: How metal-energy Markets influence green electricity investments

The world continues to face major economic challenges due to crises that have a considerable impact on energy consumption. Since the global energy crisis, energy commodity costs have risen, and economic slowdowns in various regions continue to influence electricity market trends. Clean energy markets, propelled by the growing interest of economic entities and investors, are now interconnected with several commodity markets. In this context, energy metals play a crucial role in influencing the dynamics of the clean energy and particularly electricity markets. This study takes a close look at the complex interconnections between clean energy indices and the metals market, focusing on volatility dynamics. Drawing on advanced methodologies, including the Diebold and Yilmaz method, we unveil the complex relationships that link these markets. Our results reveal distinct patterns and interactions, highlighting the nuanced nature of the connection between clean energy indices and metal prices. The insights revealed have significant implications for policymakers and investors seeking to align their strategies with sustainable energy transitions and ensure financial stability. By enhancing our understanding of the interdependencies between clean energy indices and metals markets, this research provides valuable guidance for navigating the changing clean energy investment landscape.

Cogeneration of Clean Water and Valuable Energy/Resources via Interfacial Solar Evaporation.

Water, covering over two-thirds of the Earth's surface, holds immense potential for generating clean water, sustainable energy, and metal resources, which are the cornerstones of modern society and future development. It is highly desired to produce these crucial elements through eco-friendly processes with minimal carbon footprints. Interfacial solar evaporation, which utilizes solar energy at the air-liquid interface to facilitate water vaporization and solute separation, offers a promising solution. In this review, we systematically report the recent progress of the cogeneration of clean water and energy/resources including electricity, hydrogen, and metal resources via interfacial solar evaporation. We first gain insight into the energy and mass transport for a typical interfacial solar evaporation system and reveal the residual energy and resources for achieving the cogeneration goal. Then, we summarize the recent advances in materials/device designs for efficient cogeneration. Finally, we discuss the existing challenges and potential opportunities for the further development of this field.

Dynamic Change of the Work Function of Plasma Electrode Materials due to Hydrogen Plasma exposure

It has been known that the work function of plasma electrode (PE) surfaces such as Cs-covered Mo and C12A7-electride can be decreased when the surfaces are immersed in hydrogen (or deuterium) plasma. We discovered that the work function of the C12A7-electride changed right after the termination of plasma exposure with the time constant of a few minutes. This phenomenon was not observed on the surface of clean metals (Mo or Ta). By extrapolating the dependence of work function against time to determine the value at the plasma termination, the work function during plasma exposure was estimated to be 2.4 – 2.5 eV, which can be compared with the value of the electride exhibiting metallic conductivity.

Remediation of heavy metals by native plant species grown in Iran’s richest gold mine and study of plants’ pollution tolerance strategies

Mining is defined as an environmentally hazardous activity that releases metals and other elements to the environment. Bioremediation is a natural and sustainable technique for harnessing the potential of microorganisms and plants to remove, degrade, or stabilize pollutants from contaminated sites and enable cleanup and restoration of the environment. In the present study, following the investigation of pollution of heavy metals in soil samples collected from the Zarshuran mining area, the role of twenty native plant species in the bioaccumulation of heavy metals was evaluated. After preparation of soil and plant samples, inductively coupled plasma-mass spectroscopy (ICP-MS) was used to determine the concentrations of elements in the soil and plant samples. It was confirmed that the soil samples were highly contaminated by silver (Ag), zinc (Zn), cadmium (Cd), lead (Pb), and antimony (Sb). High amounts of Pb and Zn were accumulated in Eryngium billardieri and Astragalus rostratus. Further, these two plant species could uptake, transport, and accumulate Ag in their aerial parts and the enrichment coefficient of their shoots was more than 1. Scorzonera latifolia also had good potential to stabilise Ag, Zn, and Pb in its root. As a result, E. billardieri, A. rostratus, and S. latifolia may be suitable candidate species to clean heavy metals from soils in contaminated sites. Overall, augmentation of superoxide dismutase activity and the amounts of total phenols and flavonoids in different parts of E. billardieri and A. rostratus confirmed the induction of antioxidant defense systems in the plants (compared to the control plants) and an attempt by the plants to tolerate heavy metal pollution.

Time and frequency spillovers and drivers between rare earth and energy, metals, green, and agricultural markets

This study investigates the time and frequency return and volatility spillover relationship between rare earth markets and oil, clean energy, gold, base metal, green bond, ESG, and agricultural markets by adopting the spillover indices introduced by Diebold and Yilmaz (2014) and Baruník and Křehlík (2018). As a more comprehensive view of the spillover relationship between rare earth and these industries, this study fills the gap in the existing literature on the relationship between rare earth and energy, metals, or green-related markets. Moreover, we conduct a regression analysis to reveal the drivers of the connectedness network. The empirical results suggest that the rare earth metals (REM) market is a net spillover receiver from the base metal, clean energy, and ESG markets, which are the top three net risk emitters. The network connectedness results shed light on the connections and strengths at different time horizons throughout the sample. The regression results indicate that financial condition and investor sentiment play the most significant roles in driving connectedness and have different effects at different frequencies. Furthermore, severe financial stress may increase short-term risk spillover, which indicates that investors sell out risky assets in stressful times. However, financial stress decreases long-term spillover, which implies that it damages the long-term operation of the financial market. The results could guide investors holding REM assets to balance risk and return and also provide references for policymakers to monitor market conditions and adopt policies to foster the health of the REM market.

Synergistic Approach for Selective Leaching and Separation of Strategic Metals from Spent Lithium-Ion Batteries.

Recycling spent Li-ion batteries (LIBs) is paramount to pursuing resource efficiency and environmental sustainability. This study introduces a synergistic approach for selectively leaching and separating strategic metals from waste LIBs, representing a more efficient alternative to traditional single-acid-based leaching methods. The research also thoroughly analyzes diverse extraction parameters, aiming to achieve clean metal separation through synergistic concepts rather than single-phase extraction. The outcome of this study is developing a comprehensive downstream process, advancing the cause of sustainable waste management in the LIB industry. Under specific conditions with 0.6 mol/L total acid content (0.5 mol/L tartaric acid + 0.1 mol/L ascorbic acid), 99.9% cobalt and 100% lithium were effectively leached. The subsequent extraction process achieved a clean separation, with 48.3% of cobalt extracted using a mixture of 0.1 mol/L Alamine-336-Cyanex-272 (A-336-Cy-272) from the leach liquor with no coextraction of lithium, and this efficiency was improved to 67.3% by adjusting the pH from 2.44 to 7.5. However, it is worth noting that increasing the extractant concentration led to an antagonistic effect. To further enhance cobalt enrichment in the organic phase, the McCabe-Thiele plot method was recommended, employing saponified Cy-272. Moreover, the regeneration of saponified Cy-272 was investigated, and the stripped solution was processed with NaOH to form Co(OH)2, subsequently converting it into cobalt oxide (Co3O4) through calcination.

Mechanically processed, vacuum- and etch-free fabrication of metal-wire-embedded microtrenches interconnected by semiconductor nanowires for flexible bending-sensitive optoelectronic sensors.

We demonstrate the facile fabrication of metal-wire-embedded microtrenches interconnected with semiconducting ZnO nanowires (ZNWs) through the continuous mechanical machining of micrograting trenches, the mechanical embedding of solution-processable metal wires therein, and the metal-mediated hydrothermal growth of ZNWs selectively thereto. The entire process can be performed at room or a very low temperature without resorting to vacuum, lithography, and etching steps, thereby enabling the use of flexible polymer substrates of scalable sizes. We optimize the fabrication procedure and resulting structural characteristics of this nanowire-interconnected flexible trench-embedded electrode (NIFTEE) architecture. Specifically, we carefully sequence the coating, baking, and doctor-blading of an ionic metal solution for the embedding of clean metal wires, and control the temperature and time of the hydrothermal ZNW growth process for faithful interconnections of such trench-embedded metal wires via high-density ZNWs. The NIFTEE structure can function as a bending-sensitive optoelectronic sensor, as the number of ZNWs interconnecting the neighboring metal wires changes upon mechanical bending. It may benefit further potential applications in diverse fields such as wearable technology, structural health monitoring, and soft robotics, where bending-sensitive devices are in high demand.

Assessing the linkage of energy cryptocurrency with clean and dirty energy markets

The primary objective of this study is to explore the dynamic connectedness that exists among energy cryptocurrencies, clean energy metals, and conventional dirty energies. Moreover, we aim to investigate the time-varying effects of uncertainties on the connectedness that exists among these asset classes. We uncover heterogeneous reactions among energy cryptocurrencies and other assets. Common positive co-movement clustering is revealed mostly during the periods of the cryptocurrency crash and boom in 2018 and 2020, and the oil market crash, respectively. However, a constant weak and strong co-movement over shorter and longer horizons is observed throughout the sample period for all pairs analysed, with varying outcomes for longer horizons. Combining VIX and US EPU as measures of financial and economic uncertainty, we contend that uncertainty significantly affects energy cryptocurrencies, clean and dirty energies, and clean energy metals, with relatively weak impacts or influences observed for longer investment horizons. Our findings are highly beneficial to cryptocurrency investors, alternative asset investors, and policy makers, especially during periods of market turmoil.

Metal-Organic Frameworks-Derived FeS-Co9S8/NCA Porous Aerogel Electrocatalyst as a High-Performance Cathode for Zinc-Air Batteries.

Herein, a novel strategy to establish a porous FeS-Co9S8/carbon aerogel (FeS-Co9S8/NCA) electrocatalyst for oxygen evolution reaction (OER) is fabricated via applying a green biomass carrageenan sulfuration method to CoFe-metal-organic frameworks (MOFs). The FeS-Co9S8/NCA exhibits optimized catalytic activity toward the OER with a lower overpotential of 322 mV, which is overmatched to the majority of transition metal sulfides (TMSs), as well as lifted long-term durability without evident variation in the LSV curves after 3000 cycles. Rechargeable liquid zinc-air battery (ZAB) assembled with FeS-Co9S8/NCA as the OER catalyst indicated a maximum power density of 176 mW cm-2 and superior cycling stability without raised polarization even after 48 h, outperforms commercial RuO2-based ZAB. Furthermore, the flexible solid-state ZAB built with FeS-Co9S8/NCA also demonstrated outdistance properties and bendability. The excellent performance stems from the hierarchical porous aerogel structure, which offers a multiscale mass/electron transport channel, together with the interfacial synergy effect between FeS and Co9S8, which serves as the active site of the OER reaction. Thus, this work instituted a novel strategy for obtaining both clean and efficient transition metal sulfide electrocatalysts for the OER reaction and an environmentally friendly biomass material-based sustainable electrocatalyst.

SURFACE QUALITY AND CORROSION RESISTANCE OF 316L STAINLESS STEEL ELECTROPOLISHED USING PHOSPHORIC – SULFURIC ACIDS

Electropolishing is an electrochemical surface finishing technique. It is commonly applied to equipment that requires a gleaming finish. This surface property is frequently required in 316L stainless steel (SS) medical implants. Electropolishing removes a thin layer from the metal's surface through electrochemical processes. This results in a very clean, smooth, and bright metal surface. The process parameters, such as electrolyte solution, electrical current, and electropolishing time, influence surface roughness and glossiness. The dissolution of metallic ions during the process may also affect the corrosion resistance of the treated material in addition to producing a shiny surface. This study investigated the surface glossiness, surface roughness, and corrosion of electropolished 316L SS. Electropolishing experiments on 316 SS were carried out using various H3PO4 (50%) and H2SO4 (32%) electrolyte solution compositions. The influences of electrolyte solution composition, electric current, and electropolishing time were studied. The results showed that increasing the H2SO4 content of the mixture and electropolishing the 316L SS for a longer period of time improved the surface roughness and glossiness. Under 10 Amp electric currents, the best surface glossiness was discovered. A corrosion test revealed that the electropolishing produced a Cr and Ni-rich layer that improved the corrosion resistance of the samples.

DFT Investigation of CH4 and H2O Adsorption on Pd (111), Ni (111), Pt (111), and Ir(111) Surfaces

Using density functional theory (DFT) calculations, the surface Gibbs free energy of methane and water adsorption on Pt(111), Ir(111), Ni(111), and Pd(111) surfaces was investigated. DFT computations were employed to investigate the adsorption of methane and water molecules on unit cells with varying coverage levels of 0.11, 0.25, 0.50, and 1.00 monolayers and the aggregation of H2O over clean transition metal surfaces. The adsorption configuration was assessed to experimental findings to evaluate our computational approaches' accuracy and reliability. A thermodynamic diagram was constructed for exploring the adsorption of CH4 and H2O on metal surfaces. The order of the methane adsorption energies on different metal surfaces is as follows: Pd(111) > Pt(111) > Ni(111) > Ir(111). A more significant number of H2O molecules on the transition metal surfaces reduces the contact between the metal surfaces and water molecules during water aggregation. The thermodynamic stability of water and methane adsorption coverage was found to be best on the Pt(111) surface.

Near-field heat transfer between disordered conductors

Heat transfer mediated by near-field fluctuations of the electromagnetic field was studied. In the case of metals, the latter are dominated by Coulomb interactions between thermal fluctuations of electronic density. It was shown that an elastic scattering of electrons, leading to a diffusive propagation of density fluctuations, results in a qualitative change of the radiation law. While the heat flux between clean metals follows the Stefan–Boltzmann-like T4 dependence, the heat exchange between disordered conductors is significantly enhanced and scales as T3 at low temperatures.