Interpretation of the adsorption of metals on quartz crystal based-macromolecule via advanced modeling of equilibrium isotherms

In this article, new insights about the metals-porphyrin complexes are proved by analyzing the zinc, nickel and chromium adsorption process over the well-known porphyrin macromolecule. The use of the quartz crystal microbalance (QCM) apparatus allows the control of the complexation systems’ experimental adsorption data operating at four temperatures. The experimental results and the physical models reveal that the zinc and nickel complexation processes are to be examined using the mono layer adsorption model. While, the double layer model describes the interaction between the chromium compound and the porphyrin. Actually, the three metals are shown to be adsorbed by a multi-docking process in the physicochemical description. The endothermic character of the investigated processes is shown through the appropriate data of the principal parameter adsorbent sites’ density. Hence, several porphyrin sites are exclusively stimulated at high temperature. The parameters of van del Waals, depicting the influences of the lateral interactions, explain the nickel isotherms down trend. The chemical bonds are shown to be carried out between the zinc and the porphyrin through the calculated adsorption energies. Considering the thermodynamic study, and referring to the configurational entropy and the free enthalpy, it is to be noted that the disorder peak of the three mechanisms is reached when the equilibrium concentration is equal to the energetic parameters’ values for each system. The nickel enthalpy revealed for high concentration that the adsorbates’ lateral interactions disapproved the nickel chloride adsorption. The free enthalpy trends, that observed two stability states of the chromium compound, confirmed the chromium double layer mechanism.

Criteria ruling particle agglomeration

Most of the technically important properties of nanomaterials, such as superparamagnetism or luminescence, depend on the particle size. During synthesis and handling of nanoparticles, agglomeration may occur. Agglomeration of nanoparticles may be controlled by different mechanisms. During synthesis one observes agglomeration controlled by the geometry and electrical charges of the particles. Additionally, one may find agglomeration controlled by thermodynamic interaction of the particles in the direction of a minimum of the free enthalpy. In this context, one may observe mechanisms leading to a reduction of the surface energy or controlled by the van der Waals interaction. Additionally, the ensemble may arrange in the direction of a maximum of the entropy. Simulations based on Monte Carlo methods teach that, in case of any energetic interaction of the particles, the influence of the entropy is minor or even negligible. Complementary to the simulations, the extremum of the entropy was determined using the Lagrange method. Both approaches yielded identical result for the particle size distribution of an agglomerated ensemble, that is, an exponential function characterized by two parameters. In this context, it is important to realize that one has to take care of fluctuations of the entropy.

The Straightforward Route Towards the Theoretical Specific Free Enthalpy of Electrochemical Reactions

<p></p>This paper outlines a simple yet precise method for identifying the theoretical specific free enthalpy of electrochemical reactions on basis of the ideal gas law, equilibrium thermodynamics and Faraday's law, exploiting the normative role of the standard hydrogen electrode in electrochemistry. The result of this approach are discussed in relation to four battery cell reaction examples: LiCoO₂/C₆, LiFePO₄/C₆, sodium-sulfur (NAS) and NaCl–Ni (ZEBRA). The agreement between calculated and practical values is near-excellent for even stoichiometries which bespeaks the virtually ideal nature of reversible reactions and the quality of the practical optimization efforts alike. These findings highlight the principal nature of intrinsic thermodynamic limitation to equilibrium mass transfer and its key role towards understanding reversible chemical energy storage in a global sense.<br><p></p>

Impedance Modelling of All-Solid-State Thin Film Batteries: Influence of the Reaction Kinetics

Understanding the effect of material properties on the interface impedance is crucial for high energy all-solid-state thin film lithium-ion battery design. Nevertheless, reaction kinetics determined by the free enthalpy difference...

Simulations of H–He mixtures using the van der Waals density functional

We show results on the high-pressure equation of state of hydrogen–helium mixtures obtained from finite-temperature density functional theory molecular dynamics simulations using the van der Waals density functional. We discuss the calculation of non-ideal entropies based on different methods and show how nuclear quantum corrections influence the free enthalpy of mixing. Furthermore, we calculate a Saturn isentrope based on our new equation of state data.

Processes and Responses

Thermodynamic processes involve energy exchanges in the forms of work, heat, or particles. Such exchanges might be reversible or irreversible, and they might be controlled by barriers or reservoirs. A cyclic process takes a system through several states and eventually back to its initial state; it may convert heat into work (engine) or vice versa (heat pump). This chapter defines work and heat mathematically and investigates their respective properties, in particular their impact on entropy. It discusses the roles of barriers and reservoirs and introduces cyclic processes. Basic constraints imposed by the laws of thermodynamics are considered, in particular on the efficiency of a heat engine. The chapter also introduces the thermodynamic potentials: free energy, enthalpy, free enthalpy, and grand potential. These are used to describe energy exchanges and equilibrium in the presence of reservoirs. Finally, this chapter considers thermodynamic coefficients which characterize the response of a system to heating, compression, and other external actions.

Chemical Exergy of Fuels and Efficiency Analysis of Energy Utilizations

Many studies have investigated the chemical exergy of fuels. The results showed that it is equal to the negative standard free enthalpy change (SFEC) of the fuel combustion or the correction value. However, because the products of the combustion still have the chemical potentials of diffusion, the negative SFEC is not the whole of the chemical exergy of fuels. Because the accurate entropy of fuels cannot be obtained, the accuracy of the SFEC is doubtful and some corrections become necessary. But any correction risks misrepresenting the exergy balance of fuel-fired energy systems. In this paper, some important thermodynamic fundamental problems were studied, which showed that the chemical exergy of fuels should be equal to the negative standard enthalpy change. The formulas of total entropy generations and exergy efficiencies of energy utilizations were deduced, so that the exergy efficiency evaluation just needs heat balance data. The case studies were also given.