Mechanistic insights into electric field-assisted nanofiltration for efficient lithium-magnesium separation.

Lithium, a pivotal resource in the new energy sector, demands the development of efficient and energy-saving lithium-magnesium separation technologies. This study employed electric field-assisted nanofiltration (E-NF) technology to achieve efficient lithium-magnesium separation. Compared with conventional nanofiltration, at a current density of 2 mA·cm, the rejection rate of Li⁺ decreased from -27.

Mechanism of methane activation and graphene growth on oxide ceramics.

Three-dimensional (3D) graphene materials have attracted significant attention across various fields, including energy storage and catalysis, due to their exceptional properties such as developed nanoporosity, corrosion resistance, electrical conductivity, and mechanical flexibility. The first step in synthesizing nanoporous 3D graphene involves the generation of the graphene framework through the decomposition of methane at high temperatures on thermally stable oxide ceramics. Thus, a thorough understanding of the reaction mechanism involved in this initial step is crucial.

Influence of solution stoichiometry on the thermodynamic stability of prenucleation FeS clusters.

The significance of iron sulphide (FeS) formation extends to "origin of life" theories, industrial applications, and unwanted scale formation. However, the initial stages of FeS nucleation, particularly the impact of solution composition, remain unclear. Often, the iron and sulphide components' stoichiometry in solution differs from that in formed particles.

Metal nanoparticles encapsulation within multi-shell spongy-core porous microspheres for efficient tandem catalysis.

The "one-pot" cascade process involves multiple catalytic conversions followed by a single workup stage. This method has the capability to optimize catalytic efficiency by reducing chemical processes. The key to achieving cascade reactions lies in designing cascade catalysts with well-dispersed, stably immobilized, and accessible noble metal nanoparticles for multiple catalytic conversions.

Unveiling Carbon Cluster Coating in Graphene CVD on MgO: Combining Machine Learning Force field and DFT Modeling.

In this study, we investigate the behavior of carbon clusters (C, where ranges from 16 to 26) supported on the surface of MgO. We consider the impact of doping with common impurities (such as Si, Mn, Ca, Fe, and Al) that are typically found in ores. Our approach combines density functional theory calculations with machine learning force field molecular dynamics simulations.

Comparative Investigation of the Microstructure of MgCl Aqueous Solutions Using Different X-ray Scattering Sources, Raman Spectroscopy, and Atomistic Simulations.

Aqueous solutions of magnesium chloride (MgCl(aq)) are often used to test advances in the theory of electrolyte solutions because they are considered an ideal strong 2:1 electrolyte. However, there is evidence that some ion association occurs in these solutions, even at low concentrations. Even a small ion-pairing constant can have a significant impact on the chemical speciation of ions, so it is important to determine whether ion pairing actually occurs.

The impact of stoichiometry on the initial steps of crystal formation: Stability and lifetime of charged triple-ion complexes.

Minerals form in natural systems from solutions with varying ratios of their lattice ions, yet non-stoichiometric conditions have generally been overlooked in investigations of new formation (nucleation) of ionic crystals. Here, we investigated the influence of cation:anion ratio in the solution on the initial steps of nucleation by studying positively and negatively charged triple ion complexes and subsequent particle size evolution. Our model systems are carbonates and sulfates of calcium and barium, as it was recently shown that solution stoichiometry affects the timing and rate of their nucleation.

Silicon Radical-Induced CH Dissociation for Uniform Graphene Coating on Silica Surface.

Due to the manufacturability of highly well-defined structures and wide-range versatility in its microstructure, SiO is an attractive template for synthesizing graphene frameworks with the desired pore structure. However, its intrinsic inertness constrains the graphene formation via methane chemical vapor deposition. This work overcomes this challenge by successfully achieving uniform graphene coating on a trimethylsilyl-modified SiO (denote TMS-MPS).

CO2-mineralization and carbonation reactor rig: Design and validation for in situ neutron scattering experiments-Engineering and lessons learned.

CO2 mineralization via aqueous Mg/Ca/Na-carbonate (MgCO3/CaCO3/Na2CO3) formation represents a huge opportunity for the utilization of captured CO2. However, large-scale mineralization is hindered by slow kinetics due to the highly hydrated character of the cations in aqueous solutions (Mg2+ in particular). Reaction conditions can be optimized to accelerate carbonation kinetics, for example, by the inclusion of additives that promote competitive dehydration of Mg2+ and subsequent agglomeration, nucleation, and crystallization.

Advanced Catalyst Design and Reactor Configuration Upgrade in Electrochemical Carbon Dioxide Conversion.

Electrochemical carbon dioxide reduction reaction (CO RR) driven by renewable energy shows great promise in mitigating and potentially reversing the devastating effects of anthropogenic climate change and environmental degradation. The simultaneous synthesis of energy-dense chemicals can meet global energy demand while decoupling emissions from economic growth. However, the development of CO RR technology faces challenges in catalyst discovery and device optimization that hinder their industrial implementation.

Adsorption, activation, and conversion of carbon dioxide on small copper-tin nanoclusters.

Carbon dioxide (CO) conversion to value-added chemicals is an attractive solution to reduce globally accelerating CO emissions. Among the non-precious and abundant metals tested so far, copper (Cu) is one of the best electrocatalysts to convert CO into more than thirty different hydrocarbons and alcohols. However, the selectivity for desired products is often too low.

Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?

Single-atom catalysts (SACs) on hematite photoanodes are efficient cocatalysts to boost photoelectrochemical performance. They feature high atom utilization, remarkable activity, and distinct active sites. However, the specific role of SACs on hematite photoanodes is not fully understood yet: Do SACs behave as a catalytic site or as a spectator? By combining spectroscopic experiments and computer simulations, we demonstrate that single-atom iridium (sIr) catalysts on hematite (α-FeO/sIr) photoanodes act as a true catalyst by trapping holes from hematite and providing active sites for the water oxidation reaction.

Optimal Icosahedral Copper-Based Bimetallic Clusters for the Selective Electrocatalytic CO Conversion to One Carbon Products.

Electrochemical CO reduction reactions can lead to high value-added chemical and materials production while helping decrease anthropogenic CO emissions. Copper metal clusters can reduce CO to more than thirty different hydrocarbons and oxygenates yet they lack the required selectivity. We present a computational characterization of the role of nano-structuring and alloying in Cu-based catalysts on the activity and selectivity of CO reduction to generate the following one-carbon products: carbon monoxide (CO), formic acid (HCOOH), formaldehyde (HC=O), methanol (CHOH) and methane (CH).

The carbon chain growth during the onset of CVD graphene formation on γ-AlO is promoted by unsaturated CH ends.

Chemical vapor deposition of methane onto a template of alumina (AlO) nanoparticles is a prominent synthetic strategy of graphene meso-sponge, a new class of nano porous carbon materials consisting of single-layer graphene walls. However, the elementary steps controlling the early stages of graphene growth on AlO surfaces are still not well understood. In this study, density functional theory calculations provide insights into the initial stages of graphene growth.

A Database of Solution Additives Promoting Mg Dehydration and the Onset of MgCO Nucleation.

Formed via aqueous carbonation of Mg ions, the crystallization of magnesite (MgCO) is a promising route to carbon capture and reuse, albeit limited by the slow precipitation of MgCO. Although magnesite is naturally abundant, forming at low temperature conditions, its industrial production is an energy-intensive process due to the temperatures required to prevent the formation of hydrated phases. The principal difficulty in aqueous conditions arises from the very strong Mg···HO interaction, with high barriers to Mg dehydration.

Porous nanographene formation on γ-alumina nanoparticles transition-metal-free methane activation.

γ-AlO nanoparticles promote pyrolytic carbon deposition of CH at temperatures higher than 800 °C to give single-walled nanoporous graphene (NPG) materials without the need for transition metals as reaction centers. To accelerate the development of efficient reactions for NPG synthesis, we have investigated early-stage CH activation for NPG formation on γ-AlO nanoparticles reaction kinetics and surface analysis. The formation of NPG was promoted at oxygen vacancies on (100) surfaces of γ-AlO nanoparticles following surface activation by CH.

Bridging atomistic simulations and thermodynamic hydration models of aqueous electrolyte solutions.

Chemical thermodynamic models of solvent and solute activities predict the equilibrium behavior of aqueous solutions. However, these models are semi-empirical. They represent micro-scale ion and solvent behaviors controlling the macroscopic properties using small numbers of parameters whose values are obtained by fitting to activities and other partial derivatives of the Gibbs energy measured for the bulk solutions.

Sulfate and Molybdate Incorporation at the Calcite-Water Interface: Insights from Ab Initio Molecular Dynamics.

Sulfur and molybdenum trace impurities in speleothems (stalagmites and stalactites) can provide long and continuous records of volcanic activity, which are important for past climatic and environmental reconstructions. However, the chemistry governing the incorporation of the trace element-bearing species into the calcium carbonate phases forming speleothems is not well understood. Our previous work has shown that substitution of tetrahedral oxyanions [O] ( = S and Mo) replacing [CO] in CaCO bulk phases (except perhaps for vaterite) is thermodynamically unfavorable with respect to the formation of competing phases, due to the larger size and different shape of the [O] tetrahedral anions in comparison with the flat [CO] anions, which implied that most of the incorporation would happen at the surface rather than at the bulk of the mineral.

Hydrogen-Bond Structure and Low-Frequency Dynamics of Electrolyte Solutions: Hydration Numbers from ab Initio Water Reorientation Dynamics and Dielectric Relaxation Spectroscopy.

We present an atomistic simulation scheme for the determination of the hydration number (h) of aqueous electrolyte solutions based on the calculation of the water dipole reorientation dynamics. In this methodology, the time evolution of an aqueous electrolyte solution generated from ab initio molecular dynamics simulations is used to compute the reorientation time of different water subpopulations. The value of h is determined by considering whether the reorientation time of the water subpopulations is retarded with respect to bulk-like behavior.

Density functional theory based molecular dynamics study of solution composition effects on the solvation shell of metal ions.

We present an ab initio molecular dynamics study of the alkali metal ions Li+, Na+, K+ and Cs+, and of the alkaline earth metal ions Mg2+ and Ca2+ in both pure water and electrolyte solutions containing the counterions Cl- and SO42-. Simulations were conducted using different density functional theory methods (PBE, BLYP and revPBE), with and without the inclusion of dispersion interactions (-D3). Analysis of the ion-water structure and interaction strength, water exchange between the first and second hydration shell, and hydrogen bond network and low-frequency reorientation dynamics around the metal ions have been used to characterise the influence of solution composition on the ionic solvation shell.

Reconsidering Calcium Dehydration as the Rate-Determining Step in Calcium Mineral Growth.

The dehydration of cations is generally accepted as the rate-limiting step in many processes. Molecular dynamics (MD) can be used to investigate the dynamics of water molecules around cations, and two different methods exist to obtain trajectory-based water dehydration frequencies. Here, these two different post-processing methods (direct method versus survival function) have been implemented to obtain calcium dehydration frequencies from a series of trajectories obtained using a range of accepted force fields.

Solid and Aqueous Speciation of Yttrium in Passive Remediation Systems of Acid Mine Drainage.

Yttrium belongs to the rare earth elements (REEs) together with lanthanides and scandium. REEs are commonly used in modern technologies, and their limited supply has made it necessary to look for new alternative resources. Acid mine drainage (AMD) is a potential resource since it is moderately enriched in REEs.

The full dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating.

In some molecular systems, such as nucleobases, polyenes or the active ingredients of sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale, raising questions such as: where does this energy go or among which degrees of freedom it is being distributed at such early times? Here we use transient absorption spectroscopy to track excitation energy dispersing from the optically accessible vibronic subsystem into the remaining vibrational subsystem of the solute and solvent. Monitoring the flow of energy during vibrational redistribution enables quantification of local molecular heating. Subsequent heat dissipation away from the solute molecule is characterized by classical thermodynamics and molecular dynamics simulations.

Prediction of self-assembly of adenosine analogues in solution: a computational approach validated by isothermal titration calorimetry.

The recent discovery of the role of adenosine-analogues as neuroprotectants and cognitive enhancers has sparked interest in these molecules as new therapeutic drugs. Understanding the behavior of these molecules in solution and predicting their ability to self-assemble will accelerate new discoveries. We propose a computational approach based on density functional theory, a polarizable continuum solvation description of the aqueous environment, and an efficient search procedure to probe the potential energy surface, to determine the structure and thermodynamic stability of molecular clusters of adenosine analogues in solution, using caffeine as a model.