Clean Metal Research Articles

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.

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.

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.

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.

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.

The long-term correlation between clean energy and energy metals and the role of climate policy uncertainty

ABSTRACT This study explores the potential role of climate policy uncertainty (CPU) on the long-term correlations between clean energy and different energy metals based on the DCC-MIDAS model. Our results show that CPU negatively affects the long-term correlation and will cause an additional negative impact when it increases. Moreover, risk management performance results show that energy metals are potential diversification tools for the clean energy asset and the efficiency is improved during the high-CPU period.

Energy transition metals and global sentiment: Evidence from extreme quantiles

This paper examines the quantile connectedness between energy transition metals, defined as those needed for the transition from dirty to clean energy, and global economic and financial sentiment benchmarks. Using data for five metals, - namely, aluminum, cobalt, copper, lithium, and nickel, - and two sentiment indices over 2019–2022, we empirically demonstrate that the US Economic Sentiment Index (ESI) and Societe Generale Global Sentiment Index (SGGSI) are found to be net receivers of shocks across all four extreme quantiles: 0.05, 0.10, 0.90, and 0.95. Thus, it is shown that energy transition metal markets impact global sentiment, especially during stressed periods. We also document that the total connectedness/risk spillovers between clean energy metals and sentiment indices exhibit substantial increase in the extreme quantiles. Moreover, we provide empirical evidence that there is asymmetry in spillovers over time and across quantiles.

Biotechnological strategies to recover value from waste

The demand on especially clean energy metals is growing exponentially creating a clear need to diversify the metals supply. Metal recovery from various waste deposits could be one solution to provide needed metals for the society and at the same time reduce the environmental effects of waste. Bioleaching has been commercially applied for the recovery of valuable metals from sulfidic ores, tailings and metallurgical side streams. Bioleaching approaches are still at laboratory scale for other waste streams, such as waste incineration ash, metallurgical slags and electronic waste. Adapted bioleaching strategies have been suggested for industrial and consumer metal-containing waste streams to overcome the challenges with alkalinity, heterogeneity, toxic contents, and the lack of sulfur and iron source. Integration of bioleaching with other technologies as well as integration of target waste with other material streams is one means to improve the process performance to reach higher metal yields and kinetics. Bioleaching has shown potential to decrease energy consumption and carbon footprint compared to more conventional technologies in commercial scale, which increases its attractiveness as a future technology choice.