From Grotthuss Transfer to Conductivity: Machine Learning Molecular Dynamics of Aqueous KOH.

Accurate conductivity predictions of KOH(aq) are crucial for electrolysis applications. OH is transferred in water by the Grotthuss transfer mechanism, thereby increasing its mobility compared to that of other ions. Classical and ab initio molecular dynamics struggle to capture this enhanced mobility due to limitations in computational costs or in capturing chemical reactions.

Novel pseudo-hexagonal montmorillonite model and microsecond MD simulations of hydrate formation in mixed clay sediments with surface defects.

Both CH4 hydrate accumulation and hydrate-based CO2 sequestration involve hydrate formation in mixed clay sediments. The development of realistic clay models and a nanoscale understanding of hydrate formation in mixed clay sediments are crucial for energy recovery and carbon sequestration. Here, we propose a novel molecular model of pseudo-hexagonal montmorillonite nanoparticles.

Molecular Insights into Hybrid CH Physisorption-Hydrate Formation in Spiral Halloysite Nanotubes: Implications for Energy Storage.

A microscopic insight into hybrid CH physisorption-hydrate formation in halloysite nanotubes (HNTs) is vital for understanding the solidification storage of natural gas in the HNTs and developing energy storage technology. Herein, large-scale microsecond classical molecular dynamics simulations are conducted to investigate CH storage in the HNTs via the adsorption-hydration hybrid (AHH) method to reveal the effect of gas-water ratio. The simulation results indicate that the HNTs are excellent nanomaterials for CH storage via the adsorption-hydration hybrid method.

Computational Exploration of Adsorption-Based Hydrogen Storage in Mg-Alkoxide Functionalized Covalent-Organic Frameworks (COFs): Force-Field and Machine Learning Models.

Hydrogen is a clean-burning fuel that can be converted to other forms. of energy without generating any greenhouse gases. Currently, hydrogen is stored either by compression to high pressure (>700 bar) or cryogenic cooling to liquid form (<23 K).

Effect of dissolved KOH and NaCl on the solubility of water in hydrogen: A Monte Carlo simulation study.

Vapor-Liquid Equilibria (VLE) of hydrogen (H2) and aqueous electrolyte (KOH and NaCl) solutions are central to numerous industrial applications such as alkaline electrolysis and underground hydrogen storage. Continuous fractional component Monte Carlo simulations are performed to compute the VLE of H2 and aqueous electrolyte solutions at 298-423 K, 10-400 bar, 0-8 mol KOH/kg water, and 0-6 mol NaCl/kg water. The densities and activities of water in aqueous KOH and NaCl solutions are accurately modeled (within 2% deviation from experiments) using the non-polarizable Madrid-2019 Na+/Cl- ion force fields for NaCl and the Madrid-Transport K+ and Delft Force Field of OH- for KOH, combined with the TIP4P/2005 water force field.

Mutual Diffusivities of Mixtures of Carbon Dioxide and Hydrogen and Their Solubilities in Brine: Insight from Molecular Simulations.

H-CO mixtures find wide-ranging applications, including their growing significance as synthetic fuels in the transportation industry, relevance in capture technologies for carbon capture and storage, occurrence in subsurface storage of hydrogen, and hydrogenation of carbon dioxide to form hydrocarbons and alcohols. Here, we focus on the thermodynamic properties of H-CO mixtures pertinent to underground hydrogen storage in depleted gas reservoirs. Molecular dynamics simulations are used to compute mutual (Fick) diffusivities for a wide range of pressures (5 to 50 MPa), temperatures (323.

Ultrasound enhanced diffusion in hydrogels: An experimental and non-equilibrium molecular dynamics study.

Focused ultrasound has experimentally been found to enhance the diffusion of nanoparticles; our aim with this work is to study this effect closer using both experiments and non-equilibrium molecular dynamics. Measurements from single particle tracking of 40 nm polystyrene nanoparticles in an agarose hydrogel with and without focused ultrasound are presented and compared with a previous experimental study using 100 nm polystyrene nanoparticles. In both cases, we observed an increase in the mean square displacement during focused ultrasound treatment.

Accurate Free Energies of Aqueous Electrolyte Solutions from Molecular Simulations with Non-polarizable Force Fields.

Non-polarizable force fields fail to accurately predict free energies of aqueous electrolytes without compromising the predictive ability for densities and transport properties. A new approach is presented in which (1) TIP4P/2005 water and scaled charge force fields are used to describe the interactions in the liquid phase and (2) an additional Effective Charge Surface (ECS) is used to compute free energies at zero additional computational expense. The ECS is obtained using a single temperature-independent charge scaling parameter per species.

Calculating Thermodynamic Factors for Diffusion Using the Continuous Fractional Component Monte Carlo Method.

Thermodynamic factors for diffusion connect the Fick and Maxwell-Stefan diffusion coefficients used to quantify mass transfer. Activity coefficient models or equations of state can be fitted to experimental or simulation data, from which thermodynamic factors can be obtained by differentiation. The accuracy of thermodynamic factors determined using indirect routes is dictated by the specific choice of an activity coefficient model or an equation of state.

Chemical Feedback in Templated Reaction-Assembly of Polyelectrolyte Complex Micelles: A Molecular Simulation Study of the Kinetics and Clustering.

The chemical feedback between building blocks in templated polymerization of diblock copolymers and their consecutive micellization was studied for the first time by means of coarse-grained molecular dynamics simulations. Using a stochastic polymerization model, we were able to reproduce the experimental findings on the effect of chemical feedback on the polymerization rates at low and high solution concentrations. The size and shape of micelles were computed using a newly developed software in Python conjugated with graph theory.

Computation of Electrical Conductivities of Aqueous Electrolyte Solutions: Two Surfaces, One Property.

In this work, we computed electrical conductivities under ambient conditions of aqueous NaCl and KCl solutions by using the Einstein-Helfand equation. Common force fields (charge = ±1 ) do not reproduce the experimental values of electrical conductivities, viscosities, and diffusion coefficients. Recently, we proposed the idea of using different charges to describe the potential energy surface (PES) and the dipole moment surface (DMS).

Solubilities and Self-Diffusion Coefficients of Light -Alkanes in NaCl Solutions at the Temperature Range (278.15-308.15) K and Pressure Range (1-300) bar and Thermodynamics Properties of Their Corresponding Hydrates at (150-290) K and (1-7000) bar.

Continuous Fractional Component Monte Carlo (CFCMC) and molecular dynamics (MD) simulations are performed to calculate the solubilities and self-diffusion coefficients of four light -alkanes (methane, ethane, propane, and -butane) in aqueous NaCl solutions as well as the thermodynamic properties of their corresponding hydrate crystals. Correction factors to the Lorentz-Berthelot combining rules for alkane groups (CH) and water are optimized ( = 1.04) by fitting excess chemical potentials to experimental data at 1 bar and 298.

Solving Chemical Absorption Equilibria using Free Energy and Quantum Chemistry Calculations: Methodology, Limitations, and New Open-Source Software.

We developed an open-source chemical reaction equilibrium solver in Python (CASpy, https://github.com/omoultosEthTuDelft/CASpy) to compute the concentration of species in any reactive liquid-phase absorption system. We derived an expression for a mole fraction-based equilibrium constant as a function of excess chemical potential, standard ideal gas chemical potential, temperature, and volume.

Solubility of CO in Aqueous Formic Acid Solutions and the Effect of NaCl Addition: A Molecular Simulation Study.

There is a growing interest in the development of routes to produce formic acid from CO, such as the electrochemical reduction of CO to formic acid. The solubility of CO in the electrolyte influences the production rate of formic acid. Here, the dependence of the CO solubility in aqueous HCOOH solutions with electrolytes on the composition and the NaCl concentration was studied by Continuous Fractional Component Monte Carlo simulations at 298.

A New Force Field for OH for Computing Thermodynamic and Transport Properties of H and O in Aqueous NaOH and KOH Solutions.

The thermophysical properties of aqueous electrolyte solutions are of interest for applications such as water electrolyzers and fuel cells. Molecular dynamics (MD) and continuous fractional component Monte Carlo (CFCMC) simulations are used to calculate densities, transport properties (i.e.

Electrochemical Reduction of CO to Oxalic Acid: Experiments, Process Modeling, and Economics.

We performed H-cell and flow cell experiments to study the electrochemical reduction of CO to oxalic acid (OA) on a lead (Pb) cathode in various nonaqueous solvents. The effects of anolyte, catholyte, supporting electrolyte, temperature, water content, and cathode potential on the Faraday efficiency (FE), current density (CD), and product concentration were investigated. We show that a high FE for OA can be achieved (up to 90%) at a cathode potential of -2.

A review on nature-inspired gating membranes: From concept to design and applications.

Nature has been a constant source of inspiration for technological developments. Recently, the study of nature-inspired materials has expanded to the micro- and nanoscale, facilitating new breakthroughs in the design of materials with unique properties. Various types of superhydrophobic surfaces inspired by the lotus/rice leaf are examples of nature-inspired surfaces with special wettability properties.

Electro-osmotic Drag and Thermodynamic Properties of Water in Hydrated Nafion Membranes from Molecular Dynamics.

One of the important parameters in water management of proton exchange membranes is the electro-osmotic drag (EOD) coefficient of water. The value of the EOD coefficient is difficult to justify, and available literature data on this for Nafion membranes show scattering from in experiments and simulations. Here, we use a classical all-atom model to compute the EOD coefficient and thermodynamic properties of water from molecular dynamics simulations for temperatures between 330 and 420 K, and for different water contents between λ = 5 and λ = 20.

Solubilities and Transport Properties of CO, Oxalic Acid, and Formic Acid in Mixed Solvents Composed of Deep Eutectic Solvents, Methanol, and Propylene Carbonate.

Recently, deep eutectic solvents (DES) have been considered as possible electrolytes for the electrochemical reduction of CO to value-added products such as formic and oxalic acids. The applicability of pure DES as electrolytes is hindered by high viscosities. Mixtures of DES with organic solvents can be a promising way of designing superior electrolytes by exploiting the advantages of each solvent type.

Electroreduction of CO/CO to C Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis.

Direct electrochemical reduction of CO to C products such as ethylene is more efficient in alkaline media, but it suffers from parasitic loss of reactants due to (bi)carbonate formation. A two-step process where the CO is first electrochemically reduced to CO and subsequently converted to desired C products has the potential to overcome the limitations posed by direct CO electroreduction. In this study, we investigated the technical and economic feasibility of the direct and indirect CO conversion routes to C products.

Interfacial Properties of Hydrophobic Deep Eutectic Solvents with Water.

Hydrophobic deep eutectic solvents (DESs) have recently gained much attention as water-immiscible solvents for a wide range of applications. However, very few studies exist in which the hydrophobicity of these DESs is quantified. In this work, the interfacial properties of hydrophobic DESs with water were computed at various temperatures using molecular dynamics simulations.

Vapor pressures and vapor phase compositions of choline chloride urea and choline chloride ethylene glycol deep eutectic solvents from molecular simulation.

Despite the widespread acknowledgment that deep eutectic solvents (DESs) have negligible vapor pressures, very few studies in which the vapor pressures of these solvents are measured or computed are available. Similarly, the vapor phase composition is known for only a few DESs. In this study, for the first time, the vapor pressures and vapor phase compositions of choline chloride urea (ChClU) and choline chloride ethylene glycol (ChClEg) DESs are computed using Monte Carlo simulations.

Reversible Hydrogen Storage in Metal-Decorated Honeycomb Borophene Oxide.

Two-dimensional (2D) boron-based materials are receiving much attention as H storage media due to the low atomic mass of boron and the stability of decorating alkali metals on the surface, which enhance interactions with H. This work investigates the suitability of Li, Na, and K decorations on 2D honeycomb borophene oxide (BO) for H storage, using dispersion corrected density functional theory (DFT-D2). A high theoretical gravimetric density of 8.