Surface Chemical Reactions Research Articles

First principles insights into the electronic and magnetic properties of [formula omitted] doped with VIII-group transition metal single atom

Inspired by the unprecedented surface chemical reaction activity of single-atom catalysts (SAC), this research presents a theoretical study on the doping of SnO2(110) surface with transition metal group VIII atoms (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt). Using density functional theory (DFT), the formation energy, electronic structure, charge transfer, and magnetic moments of the SnO2(110) system before and after doping were investigated. The formation energies of the different doped systems vary depending on the doping position. The doping of transition metal (TM) atoms can induce produces both charge transfer and magnetic moment. The charge transfer is largest in the Pd-doped system, with + 0.68 e at the position of the penta-coordinated Sn atom (Sn5c position) and + 0.67 e at the position of the hexa-coordinated Sn atom (Sn6c position), while the Co-doped system exhibits the smallest charge transfer of + 0.19 e (Sn6c position). Fe, Co, Ni, Ru and Os atoms introduce magnetic moments, with the Fe-doped system (Sn5c position) having the highest magnetic moments of 2.91 μB. In the SnO2(110) surface system doped with TM atoms, there are varying degrees of orbital overlap between the TM atoms and their surrounding O atoms. This theoretical work provides valuable insights into the physical properties of metal oxide based single-atom catalysts.

Sintering Mechanism and Leaching Kinetics of Low-Grade Mixed Lithium Ore and Limestone

With the rapid development of new energy fields and the current shortage of lithium supply, an efficient, clean, and stable lithium resource extraction process is urgently necessary. In this paper, various advanced detection methods were utilized to conduct a mineralogical analysis of the raw ore and systematically study the occurrence state of lithium; the limestone sintering process was strengthened and optimized, elucidating the sintering mechanism and analyzing the leaching process kinetics. Under an ingredient ratio of 1:3, a sample particle size of 300 mesh, a sintering temperature of 1100 °C, a sintering time of 3 h, a liquid–solid ratio of 2:1, a leaching temperature of 95 °C, and a leaching time of 1 h, the leaching rate of Li reached 90.04%. The highly active Ca–O combined with Si–O on the surface of β–spodumene to CaSiO4, and Al–O was isolated and combined with Li to LiAlO2, which was beneficial for the leaching process. The leaching process was controlled by both surface chemical reactions and diffusion processes, and Ea was 27.18 kJ/mol. These studies provide theoretical guidance for the subsequent re-optimization of the process.

Surface plasmon-induced various characteristics of Gold@Copper oxide nanostructures

The combined effect of metal incorporated semiconductor nanostructures (NSs) provides hybrid, proficient and more functional properties that are difficult to be provided by single component NSs in modern applications and industry. A facile seed growth method is adapted for the synthesis of gold coated by cuprous oxide (Au@Cu2O) core@shell NSs that are functionalized in their shell thickness and surface states. As synthesized Au@Cu2O core@shell cubic NSs contain single cubic Au as a core material with varying Cu2O shell thickness, confirmed by their microscopic analysis. Various spectroscopic analyses are is accomplished to confirm the chemical structure, crystallinity, oxidation state and binding energy of the concerned material over the core's surface. Optical absorption properties of core@shell NSs are greatly affected causing a shift in the surface plasmon resonance (SPR) peaks intensities with increase of the shell size. Photoluminescence (PL) spectra explain influence of Cu2O shell morphology over the emission characteristics that an increasing shell thickness caused an enhancement in PL emission peak along with red-shift of the peak. The elemental quantifying is done by XPS technique to provide a detailed surface reaction chemistry about oxidation states of copper. The charge-transfer at the metal-semiconductor interface results in highly intense and selective enhanced SERS signals via PL quenching, using Rhodamine-6G as the probe. The results provide useful information for preparation of various Au@Cu2O NSs for applications involving charge-transfer and SPR based interaction.

Antiferroelectric Heterostructures Memristors with Unique Resistive Switching Mechanisms and Properties.

A novel antiferroelectric material, PbSnO3 (PSO), was introduced into a resistive random access memory (RRAM) to reveal its resistive switching (RS) properties. It exhibits outstanding electrical performance with a large memory window (>104), narrow switching voltage distribution (±2 V), and low power consumption. Using high-resolution transmission electron microscopy, we observed the antiferroelectric properties and remanent polarization of the PSO thin films. The in-plane shear strains in the monoclinic PSO layer are attributed to oxygen octahedral tilts, resulting in misfit dislocations and grain boundaries at the PSO/SRO interface. Furthermore, the incoherent grain boundaries between the orthorhombic and monoclinic phases are assumed to be the primary paths of Ag+ filaments. Therefore, the RS behavior is primarily dominated by antiferroelectric polarization and defect mechanisms for the PSO structures. The RS behavior of antiferroelectric heterostructures controlled by switching spontaneous polarization and strain, defects, and surface chemistry reactions can facilitate the development of new antiferroelectric device systems.

Surface Development of Polyethylene Terephthalate Films Using Low-Pressure, High-Frequency Argon + Oxygen Plasma on Zinc Powder for Dye-Sensitized Solar Cells.

This research has developed a process for producing ZnO thin film from DEZn deposited onto a PET substrate with low-pressure, high-frequency Ar + O2 plasma using a chemical vapor deposition technique. The aim is to study the film production conditions that affect electrical properties, optical properties, and thin film surfaces. This work highlights the use of plasma energy produced from a mixture of gases between Ar + O2. Plasma production is stimulated by an RF power supply to deliver high chemical energy and push ZnO atoms from the cathode inside the reactor onto the substrate through surface chemical reactions. The results showed that increasing the RF power in plasma production affected the chemical reactions on the substrate surface of film formations. Film preparation at an RF power of 300 W will result in the thickest films. The film has a continuous columnar formation, and the surface has a granular structure. This results in the lowest electrical resistivity of 1.8 × 10-4 Ω. In addition, when fabricated into a DSSC device, the device tested the PCE value and showed the highest value at 5.68%. The reason is due to the very rough surface nature of the ZnO film, which increases the scattering and storage of sunlight, making cells more efficient. Therefore, the benefit of this research is that it will be a highly efficient prototype of thin film production technology using a chemical process that reduces production costs and can be used in the industrial development of solar cells.

(Industrial Electrochemistry and Electrochemical Engineering Division H. H. Dow Memorial Student Achievement Award) Tailoring Electrode-Electrolyte Interfaces through Non-Covalent Interactions for Electrochemical Energy Storage and Conversion

Li-ion batteries and fuel cells play essential roles in electrifying transportation. Central to the electrochemical systems is the electrode-electrolyte interface, where (electro)chemical surface reactions or intercalation occur, and its thermodynamic and kinetic properties determine the energy density, power density, and lifetime of the electrochemical devices. However, the molecular structures at the electrical double layer and reaction mechanisms remain poorly understood, hindering the rational material design for more efficient electrochemical devices. This talk focuses on the mechanisms of (electro)chemical reactions and charges transfer kinetics at the electrode-electrolyte interface, providing design principles based on non-covalent interactions in electrolytes.First, an in situ Fourier-transform infrared spectroscopy (FTIR) method was developed for Li-ion batteries, which revealed unique evidence for dehydrogenation of carbonate electrolytes on Ni-rich lithium nickel, manganese and cobalt oxides (NMC), accounting for interface impedance build-up and battery capacity fading. Based on the proposed mechanism, strategies on suppressing electrode and electrolyte reactivity were demonstrated to improve battery cycling. Next, the kinetic mechanism for ion intercalation at the electrode-electrolyte interface will be discussed. Li-ion concentration-dependent intercalation kinetics was demonstrated from charge-adjusted electrochemical experiments and fit into a coupled ion-electron transfer mechanism, which governed the current-dependent maximum capacity and power density of intercalation batteries. Finally, for electrocatalytic reactions central to fuel cell technologies, we demonstrated tuning interfacial hydrogen bonding through protic ionic liquids with different acid dissociation constants and organic solvents with different donor numbers to tailor oxygen-reduction reaction (ORR) and hydrogen evolution reaction (HER). Strengthening hydrogen bonding between ORR products and ionic liquids, or between interfacial water molecules facilitated proton-coupled electron transfer kinetics, revealed by in situ surface-enhanced infrared absorption spectroscopy and density functional theory (DFT) calculations. The study can pave the way for the electrolyte and electrode design of electrochemical storage devices with improved energy and power density and cycle life.

Effects and Modification Mechanisms of Different Plasma Treatments on the Surface Wettability of Different Woods

Plasma treatment of wood surfaces has shown significant effects, but different excitation methods used for different species of wood generally result in varied characteristics of wood surfaces. Secondly, plasma modification greatly enhances the absorption of liquids by wood, but the relationship between liquid absorption and surface wettability is rarely studied. Limited detailed investigation of the modification effects and mechanisms has hindered the large-scale applications of plasma treatment in the wood industry. In this study, two typical plasmas, radio frequency (RF) plasma and gliding arc discharge (GAD) plasma, were employed to treat three species of wood: poplar, black walnut, and sapele. By focusing on changes in the contact angle of the wood surface, an exponential equation fitting method is used to determine the measurement time for contact angles. The research identified that factors contributing to the decrease in contact angle after plasma modification include not only the increase in surface energy but also liquid absorption. SEM and XPS analyses demonstrate that plasma etching accelerated liquid absorption by modifying the surface topography, while the increase in surface energy was due to the addition of oxygen-containing groups. High-valence C=O and O-C=O groups serve as indicators of plasma-induced surface chemical reactions. RF modification primarily features surface etching, whereas GAD significantly increases the active surface groups. Thus, different plasmas, due to their distinct excitation modes, produce diverse modification effects on wood. Considering the various physical and chemical properties of plasma-modified wood surfaces, recommendations for adhesive use on plasma-modified wood are provided.

Electrochemical responses and surface degradation analyses alumina and feldspar dental materials in acidic environments: A comprehensive in vitro study

This in vitro study examines the electrochemical responses and surface degradation of alumina and feldspar dental ceramic materials in acidic environments using cyclic polarization and electrochemical impedance spectroscopy (EIS). Alumina and feldspar demonstrate balanced responses in both Fusayama Artificial Saliva and acidic solutions, indicating effective passivation. SEM/EDX analyses after 168-h immersion reveal significant elemental variations, suggesting complex surface phenomena and chemical reactions leading to oxide layer formation. Alumina exhibits increased Si, O, Al, Na, K, and C counts, while feldspar shows increased Si, O, Al, Na with reduced C and Ca levels, indicating complex reactions. Immersion induces notable elemental composition modifications, with alumina showing remarkable corrosion resistance and feldspar undergoing selective dissolution. This study provides insights into the electrochemical and surface degradation of these materials, emphasizing long-term stability and the need for continuous monitoring of protective layer dynamics in future research on corrosion-resistant dental biomaterials.

Controlling surface chemistry in cold sintering to advance battery materials

Cold sintering is a recently introduced densification method that is of interest due to the lower energy used in the process, the ability to densify metastable materials, the ability to integrate materials to develop unique composites, and the ability to synthesis materials that can be more easily recycled. Collectively, these advantages make cold sintering a promising approach for processing of battery components, and co-sintering into all solid-state batteries. To obtain high electrochemical performance with cold sintering, detailed control of the surface chemistry of powders is needed, to avoid or minimize the impact of carbonate formation in grain boundaries, and to limit concentrations of secondary phases that are a result of incongruent dissolution processes. In this paper, we outline the importance of surface chemical reactions of powders in cold sintering, and the mitigating processes that can be adopted to control these reactions and obtain high performance and unique opportunities for Li and Na-oxide secondary batteries. We focus on a series of examples that demonstrate how the control of low temperature densification (cold sintering) can address the environmental sensitivity of many battery materials, and highlight the issues faced and open questions. These examples include cold sintering of air-sensitive solid electrolytes, re-processing of crushed solid electrolytes, surface passivation of air-sensitive active materials for processing in air, and fabrication of solid-solid macroscopic interfaces for solid-state batteries.

Ultrasound-assisted efficient and convenient method of extracting valuable metals (Ni, Co, and Cd) from waste Ni–Cd batteries using DL-malic acid

Recycling waste Ni–Cd batteries has received much attention recently because of the serious environmental pollution they cause and to avoid the dissipation of valuable metals. Despite significant research, it is still difficult to efficiently recycle valuable and hazardous metals from waste Ni–Cd batteries in an economical and environmentally friendly manner. This study employed a novel process utilizing ultrasound-assisted leaching to recover Ni, Cd, and Co from waste nickel-cadmium (Ni–Cd) batteries. Organic DL-malic acid served as the leaching agent and H2O2 was employed as an oxidizing agent. The effects of various factors on the recovery efficiency of Ni, Cd, and Co, such as leaching temperature, time, DL-malic acid concentration, pulp density, H2O2 concentration, and ultrasound frequency, were also examined. To predict the chemical compounds present before and after the recycling experiments, the solid residues from the metal extraction were analyzed using XRD, XPS, FE-SEM, and EDS element mapping. Concurrently, ICP-OES was utilized to determine the metal content in the leachate. Under optimized conditions of 90 °C, 90 min, 2M DL-malic acid, 160 mL/g pulp density, and 20% ultrasound frequency, over 83% of Ni, 94% of Cd, and 98% of Co were effectively leached from the waste Ni–Cd battery powder. The leaching kinetics of Ni, Cd, and Co followed the surface chemical reaction control model. The activation energies (Ea) for Ni, Cd, and Co leaching were 21.34, 20.47, and 18.38 kJ/mol, respectively. The findings suggest that ultrasound-assisted leaching is an efficient, cost-effective, environmentally friendly, and sustainable alternative for extracting precious and hazardous metals from waste Ni–Cd batteries. Additionally, it reduces industrial chemical usage and enhances waste management sustainability.

Unraveling active sites regulation and temperature-dependent thermodynamic mechanism in photothermocatalytic CO2 conversion with H2O

In the photothermal synergistic catalytic conversion of CO2 and H2O, the catalyst harnesses solar energy to accumulate heat, thereby elevating the reaction system’s temperature. The influence of this temperature effect on surface chemical reactions remains an underexplored area. Here the impact of temperature on the surface-level thermodynamic reactions and conversion of CO2 with H2O on oxide semiconductors at the atomic scale was investigated using first-principle calculations. 13 different metal oxides and 5 transition metal clusters were used to introduce surface functional sites on the TiO2 supporting catalyst. The potential metal oxide cocatalysts that could be most beneficial to the following conversion of CO2 by H2O were initially screened by calculating the degrees of promotion of CO2 adsorption and activation of surface H to provide protons. The proton donation and hydrogen evolution difficulty from H2O were further analyzed, identifying transition metal cocatalysts that promote direct CO2 hydrogenation. Upon introducing bifunctional sites to facilitate adsorption and reduction, the production of CH3OH and CH4 could be further enhanced through the facilitation of the proton donation process of H2O. The results of Gibbs free-energy calculations revealed that increasing temperature enhances the reaction thermodynamics for each C1 product formation at different surface sites to varying degrees. These findings offer valuable theoretical insights for designing and regulating active sites on oxide semiconductor surfaces for efficient photothermal catalytic CO2 reduction by H2O.

Biotemplate synthesis of graphitic carbon-doped ZnO tube bundles rich in oxygen vacancies for dual-sensing of NO2/H2S at different temperatures

How to fabricate one chemiresistive sensor for highly dual-selective detection of hazardous NO2 and H2S gases is a challenge owing to the fact that the great majority of gas sensors were designed to monitor only a given harmful gas. For the aim of portable practicality and internet of things, based on green and sustainable concept, natural poplar branches were utilized as template and simply soaked in zinc nitrate solution. Subsequently, the immersed biotemplates underwent air calcination to controllably reproduce two biomorphic ZnO-based materials. Among, the hierarchical tubes (GC/ZnO) prepared by calcination at 450 °C are interconnected by 5.68 wt% in-situ graphitic carbon (GC) and uniform nanoparticles, which possess small mesopores, large specific surface area and massive oxygen vacancies. Such distinctive microstructure not only facilitates rapid gas diffusion into sensing layer and modulates the state of adsorbed oxygen species, but also exposes more active sensing units and promotes surface chemical reactions, thus realizing a portable gas sensor for highly sensing and dual-selective detection of NO2 and H2S. At lower 92 °C or 133 °C, the GC/ZnO sensor exhibits response values of 203 and 65.5 for 10 ppm NO2 or H2S gases, respectively. Meanwhile, it possesses reversible response-recovery, low detection limit, good moisture tolerance and stability during 60 days. In addition, the temperature-controlled dual-response mechanism is also analyzed.

Adsorption of dimethylaluminum isopropoxide (DMAI) on the Al2O3 surface: A machine-learning potential study

Dimethylaluminum isopropoxide (DMAI) is attracting attention as an alternative precursor for atomic layer deposition (ALD) of aluminum oxide (Al2O3). However, the surface chemical reaction mechanisms of DMAI during ALD regarding its dimeric structure under vacuum deposition process conditions has yet to be clear. In this work, the adsorption mechanism of dimeric and monomeric DMAI on a fully hydroxylated Al2O3 surface is studied using machine-learning potential (MLP) calculations. The initial adsorption of DMAI appears facile and would result in the coexistence of both methyl and isopropoxy ligands on the surface. The reactivity of DMAI is smaller than that of TMA, owing to the propensity of DMAI to adopt a dimeric form. Especially when the substrate is partially covered by other adsorbate species, the large molecular size and low reactivity of dimeric DMAI considerably hinder its reactivity toward surface adsorption. Current results are in good correspondence with the previous experimental results, where lower growth per cycle (GPC) and higher selectivity in area-selective ALD (AS-ALD) could be observed by using DMAI than compared to those of TMA processes.

Na-doped Li4SiO4 as an efficient sorbent for low-concentration CO2 capture at high temperature: Superior adsorption and rapid kinetics mechanism

Lithium silicate (Li4SiO4) sorbent has garnered attention in CO2 capture due to its high theoretical adsorption capacity and fast kinetics. However, its adsorption capacity and kinetics were hindered by low CO2 concentration. Improving adsorption performance of Li4SiO4 at low CO2 concentration has become the key to industrial application. In this work, high-activity Na-doped Li4SiO4 with controllable active substance Li3NaSiO4 was achieved. The influences of raw materials ratios on the CO2 adsorption performance were systematically investigated. When RLi/Si=4.05:1 and RNa/Si=0.15:1, the sample exhibited the highest adsorption capacity of 32.28 wt% with an equilibrium time of 29 min, and a superior stable capacity of 31.09 wt% in 15 cycles. Importantly, the double exponential fitting revealed that LiNaCO3 accelerated the ion diffusion rate and real-time adsorption processes showed Li3NaSiO4 expedited surface chemical reaction rate. Based on these, a novel Na2CO3 eutectic doping mechanism was proposed. The active substance Li3NaSiO4, generated through Na doping, along with its product formed from the reaction with CO2, molten LiNaCO3, acted synergistically to improve adsorption performance by accelerating surface chemical reaction rate and ion diffusion rate. Compared with other doped Li4SiO4, the sorbent prepared in this work demonstrated competitive adsorption performance, providing theoretical and technical support for the large-scale production of high-activity Li4SiO4.

Decomposition of zinc ferrite-based solid waste by reductive leaching: Leaching kinetics and mechanism

Zinc ferrite-based solid waste is a vital zinc and iron secondary source in view of the numerous zinc ferrite will be ineluctably produced and enters into slags or residues during zinc smelting process. In this study, a reductive leaching process with zinc sulfide powder was employed to decompose zinc ferrite from solid waste. The leaching efficiency of zinc and iron can reach 90.27 % and 81.96 %, respectively, while the process went to the 90th min at 90 ℃ under the conditions: sulfuric acid concentration of 500 g/L, liquid-to-solid ratio of 20 mL g−1, mass ratio of silver flotation tailings to zinc sulfide of 5/1, silver flotation tailings particle size of + 180–250 μm, rotary speed of 400 rpm. Then, this leaching process confirmed to shrinking core model and was conducted by surface chemical reaction after kinetics and thermodynamics investigations. Ultimately, according to various tested data, the corresponding reaction mechanism was speculated as: Fe3+ was reduced to Fe2+ by zinc sulfide and hydrogen sulfide which was the product of zinc sulfide with H+, resulting in potential reduction and H+ activity elevation, accelerating zinc dissolution eventually. Meanwhile, almost all zinc sulfide and hydrogen sulfide were oxidized to monomorphic sulfur by Fe3+ where the utilization ratio of zinc sulfide was 97.28 %.

Thermodynamics of Irreversible Processes: Fundamental Constraints, Representations, and Formulation of Boundary Conditions

Starting from the analysis of the lack of positivity of the Cattaneo heat equation, this work addresses the thermodynamic relevance of the positivity constraint in irreversible thermodynamics, that is at least as significant as the entropic constraints. The fulfillment of this condition in hyperbolic models leads to the parametrization of the concentration fields with respect to internal variables associated with the microscopic dynamics. Using Brownian motion theory as a landmark example for deriving macroscopic transport equations from the equations of motion at the particle/molecular level, we discuss two typical problems involving hydrodynamic interactions at the microscale: surface chemical reactions at a solid interface of a diffusing reactant, and mass-balance equations in a complex viscoelastic fluid, in which the physics of the interaction leads either to overcoming the parabolic diffusion model or to considering the parametrization of the concentration with respect to the degrees of freedom associated with the relaxation dynamics of the solvent fluid.

The construction of an asymmetric hybrid supercapacitor with 2D materials MXene and perovskite

The construction of an asymmetric hybrid supercapacitor with 2D materials MXene and perovskite

Universality of a surface chemical reaction network using only bi-molecular reactions

Universality of a surface chemical reaction network using only bi-molecular reactions

What Controls the Leaching of Magnesite with Concentrated Solutions of Hydrochloric or Nitric Acid?

ABSTRACT The kinetics of the leaching of natural magnesite with hydrochloric or nitric acid has been studied. Relatively high values of the apparent activation energy (from 46.5 to 70.0 kJ mol−1), but especially the low values of the apparent reaction order for H+ cations, n , have shown that the whole process is controlled by the surface chemical reaction. The value of n decreases continuously with increasing activity of H+ cations in the range of pH 5 to −1.4. At pH < 2.6 there is a transition from the kinetic regime characterized by n ≅ 0.5 to another one with n close to zero.

Simulation-based design of 1-D copper nanograting device for sensing application by studying electromagnetic properties on Cu/Air interface

Sensing devices has been an interesting area of study because of their immense application in practical life. In the present work, the extraordinary optical transmission (EOT) along with surface plasmon polaritons (SPPs) excitation at the metal/ dielectric interface is investigated RF-module of COMSOL Multiphysics 5.3a has been used to investigate copper (Cu) nanograting structure on the glass substrate in periodic arrangement of 1-dimensional (1D). The visible-infrared electromagnetic wavelength of 400–900 nm has been used to excite the SPPs at the interface and a light port is provided from the substrate side. The optimum EOT has been investigated at transmission spectra of 0th order. During this process thickness of the slit is fixed at 50 nm, the periodicity of the unit cell is fixed at 700 nm, and the width of the slit changed to check its effect on the EOT. Additionally, phenomena of near field investigation have also used to explore the transmission-based performance of field at thespecificboundary of copper (Cu) and airwhich confirm spectraoutcomesof transmission thorough the fabricated device. The optimum value of EOT foundwhenthe width of slit isat250 nm for the Cu/air interface.The deviceused for this purpose is modeled in COMSOL. Along the EOT the SPPs phenomena is also investigated by using present modeled device.These phenomena are observed by studying the electric and magnetic parts of the device that models the Cu/Air interface. We tested it with different slit widths ranging from 50-450 nm. The coupling efficiency and sensitivity of Cu/Air 1D device design at optimum slit width of 250 nm calculated. Such devices are increasingly applicable in bio photonics sensing of DNA structure, in vivo study of the internal structure of the body, imaging, surface chemical reaction, environmental remediation, and in various solar cell industries (plasmonic solar cell).