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Theoretical models have recently been used to simulate deionization technology by capturing electrochemical processes at atomistic, electrode, and plant length scales in electrodialysis, capacitive deionization using electric double layers, and Faradaic deionization using intercalation materials and redox-active polymers. We review the salient features of such models, identifying their major accomplishments in quantifying energy consumption and ion removal, analyzing the feasibility of large-scale systems, and discovering new electrode materials and understanding their deionization mechanisms. After summarizing strengths and weaknesses of recent modeling strategies, we identify research directions to expand modeling capabilities that can be used to inform electrode material/microstructure design, to assign energy losses to electrode-scale mechanisms, to bridge length scales, and to capture Faradaic kinetic/diffusion processes.

In clinics it is extremely important for implanted devices to achieve the property of enhanced lubrication and bacterial resistance; however, such a strategy has rarely been reported in previous literature. In the present study, a surface functionalization method, motivated by articular cartilage-inspired superlubrication and mussel-inspired adhesion, was proposed to modify titanium alloy (Ti6Al4V) using the copolymer (DMA-MPC) synthesized via free radical copolymerization. The copolymer-coated Ti6Al4V (Ti6Al4V@DMA-MPC) was evaluated by X-ray photoelectron spectroscopy, water contact angle, and Raman spectra to confirm that the DMA-MPC copolymer was successfully coated onto the Ti6Al4V substrate. In addition, the tribological test, with the polystyrene microsphere and Ti6Al4V or Ti6Al4V@DMA-MPC as the tribopair, indicated that the friction coefficient was greatly reduced for Ti6Al4V@DMA-MPC. Furthermore, the bacterial resistance test showed that bacterial attachment was significantly inhibited for Ti6Al4V@DMA-MPC for the three types of bacteria tested. The enhanced lubrication and bacterial resistance of Ti6Al4V@DMA-MPC was due to the tenacious hydration shell formed surrounding the zwitterionic charges in the phosphorylcholine group of the DMA-MPC copolymer. In summary, a bioinspired surface functionalization strategy is developed in this study, which can act as a universal and promising method to achieve enhanced lubrication and bacterial resistance for biomedical implants.

Titanium and its alloys have long been used as implantable biomaterials in orthopedics; however, to the best of our knowledge, few studies were reported to investigate surface functionalization of titanium for enhanced lubrication and sustained drug release. In the present study, titania nanotube arrays (TNTs) were prepared by anodization as effective drug nanocarriers, using titanium as the substrate. Meanwhile, motivated by articular cartilage-inspired superlubricity and mussel-inspired adhesion, a copolymer containing both dopamine methacrylamide and 2-methacryloyloxyethyl phosphorylcholine was synthesized (DMA-MPC) and spontaneously grafted onto the TNT surface, which was validated by characterization techniques such as scanning electron microscopy, water contact angle measurements, and X-ray photoelectron spectroscopy. Additionally, the lubrication test showed that copolymer-grafted TNTs have remarkably reduced friction coefficients compared with bare TNTs. Furthermore, the drug release test demonstrated that copolymer-grafted TNTs inhibited burst drug release and achieved sustained drug release in comparison with bare TNTs. In conclusion, the bioinspired surface functionalization strategy developed here, namely DMA-MPC copolymer-grafted TNTs, can be applied to modify orthopedic biomaterials (such as titanium) for enhanced lubrication and sustained drug release.

Prussian blue analogues (PBAs) are model host compounds for the intercalation of monovalent cations for electrochemical energy storage and separations. However, the interactions among interstitial species and their effects on atomic arrangements therein are understood mainly at a phenomenological level. Analyzing correlations between electronic interactions and polyatomic arrangements in hydrated Prussian blue analogues is complicated by the nonlocal hydrogen-bonding interactions between zeolitic water and framework lattices. Here, we train machine-learning (ML) models to learn DFT-calculated energy landscapes of nickel hexacyanoferrate PBA lattices with various lattice hydration degrees, oxidation states, and types of intercalated alkali cations based on various three-particle feature parameters. This ML approach is enabled by using gradient-boosted regression trees with features that are rotationally invariant geometric parameters. ML model accuracy is shown to be a cation-specific indicator of correlations between energy and polyatomic arrangements. Overlap population analysis among correlated atoms further confirms that such correlations are caused by the competition for dative bonding between Lewis-acid intercalated cations and Lewis bases (cyanide and oxygen in ${\mathrm{H}}_{2}\mathrm{O}$). Examination of lowest-energy structures reveals that cation hydrophilicity and bare ionic radius determine dative-bonding strength, resulting in cation-${\mathrm{H}}_{2}\mathrm{O}$ ordering in interstitial space. The projected energy landscapes of hydrated PBA lattices is also explored in subspaces spanned by certain many-particle feature parameters inspired by ML analysis. The downhill traces in such landscapes indicate that lattice distortion is accompanied by two kinds of collective movements: (1) rearrangements in the hydration shells around small and hydrophilic cations and (2) collective attack of ${\mathrm{H}}_{2}\mathrm{O}$ molecules on nickel-cyanide bonds promoted by large, hydrophobic cations.

Elastomers such as gels and rubbers play various roles in our lives. Elastomers, which guarantee the safety of airplanes and automobiles and the stability of buildings, are materials that have made the lives of people in the twentieth century extremely convenient. The existence of macromolecules, that is, giant molecules, has been clarified; the development of synthetic macromolecules has progressed; and understanding of elastomers has progressed. By introducing new ideas, it has become possible to obtain tough and hard elastomers, which was difficult under conventional ideas. In this paper, we will explain the development from the classical theory of elastomers to current efforts., Graphical Abstract

Prussian blue analogues (PBAs) are promising cation intercalation materials for electrochemical desalination and energy storage applications. Here, we investigate the mechanism of capacity fade and degradation of nickel hexacyanoferrate (NiHCFe) during galvanostatic cycling in aqueous electrolytes that are rich in either Mg2+ or Ca2+. We combine experimental characterization, first principles electronic structure calculations, statistical mechanics and lattice-percolation modeling of electron transfer to elucidate the mechanisms responsible for the degradation of NiHCFe and its partial retention of capacity. Electrochemical characterization of porous NiHCFe electrodes suggests a two-site intercalation mechanism, while spectroscopy reveals the presence of Ni2+ and Fe(CN)63− ions in the electrolyte post cycling in Mg2+(aq). Using simple coprecipitation reactions, we show that Mg2+ and Ni2+ can coexist in the lattice framework, forming stable PBAs. Galvanostatic cycling of these PBAs shows that the presence of Mg2+ in the lattice framework results in the dissolution of Mg1.5FeIII(CN)6 in water during oxidation. We propose that Mg2+ can partially substitute Ni2+ ions in the lattice framework during galvanostatic cycling, displacing the substituted Ni2+ ions into interstitial sites. Based on differential capacitance analysis we show that Mg2+ intercalates into interstitial sites at ∼0.45 V vs. Ag/AgCl and it displaces Ni2+ in the lattice framework at ∼0.05 V vs. Ag/AgCl. Substitution of Ni2+ leads to Fe(CN)63− and Ni2+ ions being removed into the electrolyte during oxidation. Using first principles density functional theory (DFT) calculations combined with a statistical mechanics model, we verify the thermodynamic feasibility of the proposed reaction mechanism and predict the fraction of Ni2+ ions being substituted by Mg2+ during intercalation. Further, analysis of the electron density distribution and local density of states indicates that Mg2+ ions can act as insulating defects in the lattice framework that render certain Fe ions electrically inactive and likely contribute to capacity fade along with dissolution of Fe(CN)63−.

Lithium-sulfur batteries are very promising next-generation energy storage batteries due to their high theoretical specific capacity. However, the shuttle effect of lithium-sulfur batteries is one of the important bottlenecks that limits its rapid development. Herein, physical and chemical dual adsorption of lithium polysulfides are achieved by designing a novel framework structure consisting of MnO2, reduced graphene oxide (rGO), and carbon nanotubes (CNTs). The framework-structure composite of MnO2/rGO/CNTs is prepared by a simple hydrothermal method. The framework exhibits a uniform and abundant mesoporous structure (concentrating in ~12 nm). MnO2 is an &alpha, phase structure and the &alpha, MnO2 also has a significant effect on the adsorption of lithium polysulfides. The rGO and CNTs provide a good physical adsorption interaction and good electronic conductivity for the dissolved polysulfides. As a result, the MnO2/rGO/CNTs/S cathode delivered a high initial capacity of 1201 mAh g&minus, 1 at 0.2 C. The average capacities were 916 mAh g&minus, 1, 736 mAh g&minus, 1, and 547 mAh g&minus, 1 at the current densities of 0.5 C, 1 C, and 2 C, respectively. In addition, when tested at 0.5 C, the MnO2/rGO/CNTs/S exhibited a high initial capacity of 1010 mAh g&minus, 1 and achieved 780 mAh g&minus, 1 after 200 cycles, with a low capacity decay rate of 0.11% per cycle. This framework-structure composite provides a simple way to improve the electrochemical performance of Li-S batteries.

The addition of nanoparticles to water-based lubricants is a commonly used method to improve lubrication, but to the best of our knowledge few studies have been reported to investigate the lubrication property of surface-modified nanodiamonds (ND) with polyzwitterionic brushes. In this study, a bioinspired copolymer containing dopamine and 2-methacryloyloxyethyl phosphorylcholine (MPC) was synthesized (DMA-MPC) and then spontaneously grafted onto the ND surface (ND-MPC) through simple stirring in order to enhance lubrication. The characterization of transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis indicated that the DMA-MPC was successfully modified on the ND surface. Furthermore, a series of tribological experiment were performed on a universal materials tester using glycerol, glycerol + ND, and glycerol + ND-MPC as the lubricants. It was found that the addition of ND to the lubricant (i.e., glycerol + ND and glycerol + ND-MPC) significantly reduced wear with a smaller wear scar and wear track on the tribopairs, and the coefficient of friction further decreased by about 40% when using glycerol + ND-MPC as the lubricant, which could be attributed to the hydration lubrication of the polyzwitterionic brushes modified on the ND surface and the rolling effect of nanoparticles. In conclusion, in this study a universal and versatile surface modification method was proposed on the basis of the synthesis of bioinspired copolymer DMA-MPC, which remarkably enhanced the lubrication property of ND nanoparticles when added to water-based lubricants.

Electrochemical desalination devices that use redox-active cation intercalation electrodes show promise for desalination of salt-rich water resources with high water recovery and low energy consumption. While previous modeling and experiments used ion-exchange membranes to maximize charge efficiency, here a membrane-free alternative is evaluated to reduce capital cost by using a porous diaphragm to separate Na$_{1+x}$NiFe(CN)$_6$ electrodes. Two-dimensional porous-electrode modeling shows that, while charge efficiency losses are inherent to a diaphragm-based architecture, charge efficiency values approaching the anion transference number (61$\%$ for NaCl) are achievable for diaphragms with sufficiently low salt conductance. Closed-form equations are thereby derived that relate charge efficiency to the non-dimensional P\`{e}clet and Damk\"ohler numbers that enable the selection of current and flow velocity to produce a desired degree of desalination. Simulations using these conditions are used to quantify the tradeoffs between energy consumption and salt removal rate for diaphragm-based cells operated at a range of currents. The simulated distributions of reactions are shown to result from the local salt concentration variations within electrodes using diffusion-potential theory. We also simulate the cycling dynamics of various flow configurations and show that flow-through electrodes exceed the degree-of-desalination compared with flow-by and flow-behind configurations due to solution stagnation within electrodes.