Adsorption Of H2O Research Articles

Enhanced Alkaline Hydrogen Evolution Reaction via Electronic Structure Regulation: Activating PtRh with Rare Earth Tm Alloying.

Developing high-performance electrocatalysts for alkaline hydrogen evolution reaction (HER) is crucial for producing green hydrogen, yet it remains challenging due to the sluggish kinetics in alkaline environments. Pt is located near the peak of HER volcano plot, owing to its exceptional performance in hydrogen adsorption and desorption, and Rh plays an important role in H2O dissociation. Lanthanides (Ln) are commonly used to modulate the electronic structure of materials and further influence the adsorption/desorption of reactants, intermediates, and products, and noble metal-Ln alloys are recognized as effective platforms where Ln elements regulate the catalytic properties of noble metals. Here Pt1.5Rh1.5Tm alloy is synthesized using the sodium vapor reduction method. This alloy demonstrates superior catalytic activity, being 4.4 and 6.6 times more effective than Pt/C and Rh/C, respectively. Density Functional Theory (DFT) calculations reveal that the upshift of d-band center and the charge transfer induced by alloying promote adsorption and dissociation of H2O, making Pt1.5Rh1.5Tm alloy more favorable for the alkaline HER reaction, both kinetically and thermodynamically.

Carbon Dioxide Pressure and Catalyst Quantity Dependencies in Artificial Photosynthesis of Hydrocarbon Chains on Nanostructured Co/CoO Surfaces.

In this study, we investigated the influence of pressure and the quantity of Co/CoO catalyst on an artificial photosynthesis process that converts CO2 and H2O into hydrocarbons (CnH2n+2, where n ≤ 18). The adsorption of CO2 and H2O on Co/CoO surfaces proved to be pivotal in this photo-catalytic reaction. Photoexcited carbon dioxide and water molecules ((CO2)* and (H2O)*) generated by illuminating the catalyst surface led to the formation of alkene hydrocarbon molecules with carbon numbers following an approximate Poisson distribution. The optimal pressure was found to be 0.40 MPa. Pressure less than 0.40 MPa resulted in low CO2 adsorption, impeding excitation for photosynthesis. At greater pressure, oil/wax accumulation on Co/CoO surfaces hindered CO2 adsorption, limiting further photosynthesis reactions. The average number of carbon atoms in the hydrocarbons and hydrocarbon yield were correlated. The amount of Co/CoO was also found to affect the hydrocarbon yield. Our study contributes to the understanding of Co/CoO-catalyzed photosynthesis and suggests that an open-flow system could potentially enhance the productivity of long-chain hydrocarbons.

Ionic hyper-cross-linked porous polymer networks with achiral and chiral pyridinium-type segments

A new type of ionic porous polymer networks (PPNs) is reported containing (i) N-alkyl pyridinium bromide ionic groups and (ii) a hyper-cross-linked scaffold based on polyacetylene (polyene) chains the rigidity of which contributes to the permanent porosity the PPNs. The ionic PPNs were prepared by a combination of chain-growth polymerization of acetylenic monomers and quaternization reactions of pyridine and alkyl bromide moieties. The wide variability of this synthetic concept enabled the preparation of covalently diverse PPNs with ionic groups located either in the pendant groups or in the knots of the networks, as well as the preparation of PPNs with chiral ionic groups. The content of ionic groups in PPNs ranged from 1.5 to 4.2 mmol/g, and the BET area was from 67 to 744 m2/g. The mode of quaternization used (prepolymerization or postpolymerization) controlled the contribution of micropores and mesopores to the porosity of the ionic PPNs. The polyacetylene ionic PPNs were active as heterogeneous organocatalysts (applied without a cocatalyst) for the cycloaddition of CO2 to styrene oxide yielding styrene carbonate as the only product (up to 96 %). PPNs with chiral ionic groups showed potential for enantioselective catalysis of this reaction. The catalytic activity was controlled by the accessibility of pyridinium active centres for the substrate molecules. Ionic PPNs prepared were also efficient in reversible water vapour capturing and releasing (capacity up to 361 mg/g at 298 K and RH = 90 %). Both surface adsorption and capillary condensation of H2O contributed to the water vapour capture on reported PPNs.

Diffusivity of CO2 in H2O: A Review of Experimental Studies and Molecular Simulations in the Bulk and in Confinement.

An in-depth review of the available experimental and molecular simulation studies of CO2 diffusion in H2O, which is a central property in important industrial and environmental processes, such as carbon capture and storage, enhanced oil recovery, and in the food industry is presented. The cases of both bulk and confined systems are covered. The experimental and molecular simulation data gathered are analyzed, and simple and computationally efficient correlations are devised. These correlations are applicable to conditions from 273 K and 0.1 MPa up to 473 K and 45 MPa. The available experimental data for diffusion coefficients of CO2 in brines are also collected, and their dependency on temperature, pressure, and salinity is examined in detail. Other engineering models and correlations reported in literature are also presented. The review of the simulation studies focuses on the force field combinations, the data for diffusivities at low and high pressures, finite-size effects, and the correlations developed based on the Molecular Dynamics data. Regarding the confined systems, we review the main methods to measure and compute the diffusivity of confined CO2 and discuss the main natural and artificial confining media (i.e., smectites, calcites, silica, MOFs, and carbon materials). Detailed discussion is provided regarding the driving force for diffusion of CO2 and H2O under confinement, and on the role of effects such as H2O adsorption on hydrophilic confining media on the diffusivity of CO2. Finally, an outlook of future research paths for advancing the field of CO2 diffusivity in H2O at the bulk phase and in confinement is laid out.

Attempts of B-site doped LaFeO3 oxygen carriers in high-moisture content biomass chemical looping gasification

With the rapid development of anaerobic digestion engineering, the disposal and utilization of digestate are urgently required. Chemical looping gasification (CLG) technology provides potential for eliminate digestate and convert it into high-quality syngas. However, the application of conventional CLG is hindered by the high-moisture content of digestate. In order to decrease the energy consumption of dehydration, this work aims to optimize the CLG process by developing new oxygen carrier (OC) to enhance the transition of self-moisture of digestate. LaFeO3 was employed as the basic OC and Cr, Co, Cu were further doped on the B-site to form LaB0.5Fe0.5O3 (B = Cr, Co, Cu). H2O-TPD, OH/FTIR, NH3-Drifts, Raman, and XPS were employed to analyze the adsorption and dissociation of H2O by different OCs. Results indicated that LaFeO3 and LaB0.5Fe0.5O3 exhibited a synergistic effect with H2O, enabling adsorption of H2O at low temperatures and dissociation at high temperatures. In this case, it allows OC to capture H2O in the initial drying stage, then release H2O and OH at higher temperatures to participate in subsequent reactions, thus significantly increase the gasification performance. Fixed-bed CLG experiments were conducted to corroborate the characterization results. LaCu0.5Fe0.5O3 showcased the best gasification effect, achieving 81.83 % efficiency at a digestate moisture content of 40 %, surpassing LaFeO3 CLG by 5 %. Moreover, LaCu0.5Fe0.5O3 exhibited a noticeable catalytic effect and lowered the activation energy (E). Kinetic analysis revealed a 16 % reduction in E for LaCu0.5Fe0.5O3 CLG in comparison to LaFeO3 CLG.

Aqueous phase reforming of methanol for hydrogen production over highly-dispersed PtLa/CeO2 catalyst prepared by photochemical reduction method

Hydrogen production by catalytic aqueous phase reforming (APR) of biomass oxygenated derivatives in relatively mild conditions is a promising way to produce hydrogen. In this work, Pt/CeO2-HT, Pt/La–CeO2-HT and PtLa/CeO2 catalysts were synthesized by a novel photochemical reduction method and applied to the methanol APR. Extensive characterizations have proved that the mild catalyst preparation method gave it a high dispersion of Pt species and the addition of La modified the metal-support interaction. The results showed that La-modified Pt/La–CeO2-HT and PtLa/CeO2 catalysts exhibited better catalytic performance than the Pt/CeO2-HT catalyst, among which the hydrogen yield was the highest for the surface La-modified PtLa/CeO2 catalyst (177.7 mmol/gcat). This was mainly attributed to the surface modification of La resulted in a significant increase in the number of moderately strong basic sites and surface oxygen vacancies in the PtLa/CeO2 catalyst. The enhancement of catalyst basicity effectively promoted the dissociation of H2O to produce hydroxyl groups, while a large number of surface oxygen vacancies provided more active sites for the adsorption and dissociation of H2O. And their synergistic behavior efficiently facilitated the water gas shift (WGS) reaction, resulting in a significant increase in hydrogen yield of methanol APR. Associated with the in situ DRIFTS analyzes and the results indicated by WGS reaction, possible promotion mechanism was proposed.

Synergistic interactions of electronic modulation and low crystallization in Ru-RuO2/C heterostructure for highly efficient multifunctional electrocatalysis

Developing electrocatalysts with multifunctional performance is crucial for hydrogen energy storage and conversion, but still a great challenge. Herein, an efficient trifunctional electrocatalyst with heterostructure is fabricated by a sequential reduction and annealing approach. With different annealing atmospheres, Ru-RuO2/C electrocatalysts having different Ru/RuO2 atomic ratios or different crystallinities were achieved. Among these electrocatalysts, Ru-RuO2/C annealed from N2-air mixed atmosphere (Ru-RuO2/C 250NA) displays the most excellent performance, affording overpotential values of 30.63 mV for alkaline hydrogen evolution reaction (HER) and 273.42 mV for alkaline oxygen evolution reaction (OER) at 10 mA cm−2, much lower than those of state-of-the-art Pt/C (η10, HER = 46.57 mV) and RuO2 (η10, OER = 288.99 mV). Not only that, it also delivers favorable activity for alkaline hydrogen oxidation reaction (HOR), with 2.1 times of mass specific exchange current density than that of Pt/C. The experimental and theoretical investigations prove the electron rearrangement at Ru and RuO2 interface with abundant defects and amorphous/crystalline structures. The synergistic effect of dual active sites simultaneously optimizes H and OH as well as H2O adsorption energies, endowing the Ru-RuO2/C 250NA as the preferential electrocatalysts.

Synchronous construction of Cu and Ni single-atom sites in ordered porous TiO2 for enhanced photo-conversion of CO2 and H2O to methane

The solar-powered conversion of CO2 and H2O to hydrocarbons is highly compelling but remains a significant challenge because both CO2 reduction and H2O oxidation are thermodynamically unfavorable. Herein, the synchronous incorporation of Cu and Ni single-atom sites into ordered porous TiO2 was accomplished through a template-assisted calcination process, resulting in a series of Cu-Ni/TiO2 catalysts for photocatalytic CO2 reduction using H2O as a hydrogen source. The formation of Cu and Ni single atoms was verified by X-ray absorption fine structure (XAFS) spectroscopy. The optimal Cu-Ni/TiO2 photocatalyst exhibited excellent performance to reach a CH4 production rate of 63.88 μmol g−1 h−1 with a high selectivity of 96.4% under simulated sunlight, in the absence of sacrificial agents. The presence of Cu and Ni single atoms not only provided effective active sites for adsorption and activation of CO2 and H2O but also facilitated separation and transfer of photogenerated charge carriers. In situ spectroscopic analyses revealed that CO2 was adsorbed on the catalyst as bicarbonates, followed by the multistep reduction into CH4 via the electron-proton transfer processes, while the photogenerated holes were consumed by H2O oxidation to generate H2O2. The simultaneous enhancement of both H2O and CO2 activation guarantees excellent photocatalytic performance towards CH4 production. This study provides guidance on developing highly efficient photocatalysts by engineering active sites as well as insights into enhancing CO2 photoreduction.

How does calcium carbonate enhance pollutants degradation under light illumination? Enhanced scattering and hydroxyl radical

Some trace pollutants exist extensively in the water, soil and other environment, as a result of unorganized emissions. The natural mineral CaCO3 is also widely found in these environments. In this study, we studied the effect of CaCO3 on the transformation of pollutants in water under light and the inactivation of bacteria in different environments. The photolysis of tetracycline (TC) under sunlight in the presence of CaCO3 can be as high as about 77%, which was improved comparing with the pure photolysis under sunlight (15%) and adsorption (32%). The same trend was found when the natural minerals containing CaCO3 (e.g. shell, oyster shell, limestone and marble) were adopted. It was determined that 1.10×10−5 mmol L−1 of ∙OH can be produced under Xenon lamp light source (HID) illumination after 2 h of reaction, which was increased to 4.28×10−5 mmol L−1 in the HID system with addition of CaCO3. According to the calculation by projector-enhanced wave (PAW) method, it was found that the O-H bond length was increased after H2O adsorption on CaCO3. The O-H bond cleavage was easier for more ∙OH generation under light illumination. Based on ZEMAX software simulations, CaCO3 can act as light scatterer and increase the residence time of light in solution.

Regulation of Electronic Structures of the Urchin-Like NiCoP/CoP Nanocatalysts for Fast Hydrogen Evolution.

The exploration of stable, efficient, and low-cost catalysts toward ammonia borane hydrolysis is of vital significance for the practical implementation of this hydrogen production technology. Integrating interface engineering and nano-architecture engineering is a favorable strategy to elevate catalytic performance, as it can modify the electronic structure and provide sufficient active sites simultaneously. In this work, urchin-like NiCoP/CoP heterostructures are prepared via a three-step hydrothermal-oxidation-phosphorization synthesis route. It is demonstrated that the original Ni/Co molar ratio and the amount of phosphorus are crucial for adjusting the morphology, enhancing the exposed surface area, facilitating charge transfer, and modulating the adsorption and activation of H2O molecules. Consequently, the optimal Ni1Co2P heterostructure displays remarkable catalytic properties in the hydrolysis of ammonia borane with a turnover frequency (TOF) value of 30.3 molH2 ⋅ min-1 ⋅ molmetal -1, a low apparent activation energy of 25.89 kJ ⋅ mol-1, and good stability. Furthermore, by combining infrared spectroscopy and isotope kinetics experiments, a possible mechanism for the hydrolysis of ammonia borane was proposed.

DFT evaluation the photo-catalytic performance of g-C3N4 dots/ZnO with O/S doping

To develop the high-performance g-C3N4-based photo-catalysts and understand the mechanism of photo-catalytic degradation of volatile organic compounds (VOCs), we evaluated the photo-catalytic performance and corresponding catalytic mechanisms of g-C3N4 dots/ZnO (CNZO) systems using density functional theory (DFT) calculations. Our results showed that the combination of g-C3N4 dots and ZnO monolayer has a appropriate band gap and strong visible light absorption, significantly enhancing photoelectron excitation and immigration. We also observed that O/S doping exerted a significant impact on the band structure and interfacial coupling, thereby increasing the number of photoelectrons that move from the valence band (VB) of ZnO monolayer to the conduction band (CB) of g-C3N4 dots, thereby enhancing the separation of photo-generated electron-hole pairs in O/S-CNZO. Furthermore, the suitable CB and VB positions of O/S-CNZO encourage the adsorption of surface H2O and O2 molecules, leading to the generation of ·OH and ·O2− radicals crucial in VOCs degradation. This work introduces new approaches and perspectives for constructing novel photo-catalysts. Additionally, it involves a theoretical evaluation of the photo-catalytic performance of O/S-CNZO.

Highly Selective Hydrogenation of Unsaturated Aldehydes in Aqueous Phase.

Chemoselective hydrogenation of carbonyl in unsaturated aldehydes is a significant process in the chemical industry, in which the development of aqueous-phase reaction systems as a substitution to organic ones is challenging. Herein, we report Ir atomic cluster catalysts anchored onto WO3-x nanorods via a reduction treatment at various temperatures (denoted as Ir/WOx-T, T = 200, 300, 400, and 500 °C), which accelerates the chemoselective hydrogenation of carbonyl groups in aqueous solutions. The optimal catalyst Ir/WOx-300 exhibits exceptional activity (TOF value: 1313.7 min-1) and chemoselectivity toward cinnamaldehyde (CAL) hydrogenation to cinnamyl alcohol (COL) (yield: ∼98.0%) in water medium, which is, to the best of our knowledge, the highest level compared with previously reported heterogeneous catalysts in liquid-phase reaction. Ac-HAADF-STEM, XAFS, and XPS verify the formation of interface structure (Irδ+-Ov-W5+ (0 ≤ δ ≤ 4); Ov denotes oxygen vacancy) induced by metal-support interaction and the largest concentration of interfacial Ir (Irδ+) in Ir/WOx-300. In situ studies (Raman, FT-IR), isotopic labeling measurements combined with DFT calculations substantiate that the hydrogenation of the C=O group consists of two pathways: water-mediated hydrogenation (predominant) and direct hydrogenation via H2 dissociation (secondary). In the former case, W5+-Ov site accelerates the activation adsorption of H2O, while Ir0 site facilitates the H-H bond cleavage of H2 and Irδ+ promotes the CAL adsorption. H2O molecule, as the source of hydrogen species, participates directly in the hydrogenation of the carbonyl group through a hydrogen-bonded network, with a largely reduced energy barrier relative to the H2 dissociation path. This work demonstrates a green catalytic route that breaks the activity-selectivity trade-off toward the selective hydrogenation of unsaturated aldehydes, which shows great potential in heterogeneous catalysis.

An in-depth revelation of a novel facilitation mechanism of H2O on the NH3-SCR reaction of Mn-Ce/TiO2 catalyst with exposed anatase {001} facets

H2O typically has a detrimental impact on the NH3-SCR reaction, exacerbating the sulfur poisoning of the catalysts. This study thoroughly explores the unusual facilitating mechanism of H2O (gas) (g) at low concentrations (volume fraction less than 3.5 vol%) on the NH3-SCR reaction of a Mn-Ce/TiO2 (M−C/Ti) catalyst with preferential exposure of the anatase {001} facets (M−C/Ti-001) through comprehensive experimental characterization and DFT (Density functional theory) calculations. The optimum water vapor promotion concentration of 2.5 vol% was experimentally determined. It generated new Brønsted acid sites after H2O adsorption on the anatase {001} facets, increasing the activity of the Lewis acid sites and the NH3 adsorption capacity on Brønsted acid sites (B-NH4+). B-NH4+ species can react with NO2 in a fast SCR reaction, significantly enhancing the overall reaction rate. The low content of H2O (g) contributes to the inert linear nitrite involved in the NH3-SCR reaction, which is favourable for the NH3-SCR reaction. In addition, the Brønsted acid sites effectively inhibited the adsorption of SO2 onto the surface of the M−C/Ti-001 catalyst, enhancing its sulfur resistance. This study provides new insights into the promotion mechanism of M−C/Ti-001 catalysts by low concentration of water vapor.

Constructing unsaturated coordination Co−M (M = P, S, Se, Te) bonds modified metallic Co for efficient alkaline hydrogen evolution

Alkaline hydrogen evolution reaction (HER) provides a promising approach for producing green hydrogen, but designing high-efficiency transition metal nanocatalysts is rather challenging. Herein, unsaturated coordination Co−M (M = P, S, Se, Te) bonds modified metallic Co are designed on Ni foam (M-Co/NF) through a facile electrodeposition strategy. The constructed Co−M bonds not only alter the local coordination condition and electron structure, but also provide an electron transfer channel, and significantly enhance the intrinsic activities. Consequently, the P-Co/NF displays an ultralow overpotential of 23 mV at 10 mA cm−2 with excellent stability. X-ray absorption spectroscopy verifies the formation of extremely unsaturated coordination Co−P bonds, which adjusts the charge redistribution. Density functional theory calculations prove the unsaturated coordination Co−P bonds can optimize the adsorption of H2O and H adsorption. This work provides novel insight into the effects of local coordination environment on activity and the rational design of efficient transition metal nanocatalysts.

An interfacial C-S bond bridged S-scheme ZnS/C3N5 for photocatalytic H2 evolution: Opposite internal-electric-field of ZnS/C3N4, increased field strength, and accelerated surface reaction

An interfacial C-S bond bridged ZnS/C3N5 heterojunction was constructed for photocatalytic H2 evolution. Different from traditional type-II ZnS/C3N4 heterojunction, the electron transfer followed S-scheme pathway, due to opposite internal-electric-field (IEF) directions in these two heterojunctions. The C-S bond formation was carefully investigated, and they were susceptive to the preparation temperatures. In photocatalytic reaction, C-S bond was functioned as the “high-speed channel” for electron separation and transfer, and the IEF strength in ZnS/C3N5 was 1.86 × 108 V/m, 2.6 times higher than that in ZnS/C3N4. Moreover, the C-S bond also altered the surface molecular structure of ZnS/C3N5, and hence the surface reaction was accelerated via improving H2O adsorption and activation behaviors. Benefiting from the S-scheme pathway, enhanced IEF strength, and accelerated surface reaction, the photocatalytic H2 production over ZnS/C3N5 reached up to 20.18 mmol/g/h, 3.2 and 2.5 times higher than those of ZnS/C3N4 and ZnS/C3N5-300 without C-S bond.

Investigation of the microscopic mechanism of H2O adsorption by low-rank coal slit pores through GCMC and MD simulations

This study investigates the influence of pore structure on H2O adsorption in low-rank coal (LRC) models at a molecular level, employing variously sized LRC slit-pore models·H2O adsorption behavior is analyzed across different pore sizes ranging from 0.001 to 100 kPa fugacity, by employing the Grand canonical Monte Carlo (GCMC) method and molecular dynamics (MD) simulations to explore saturated adsorption kinetics. The findings indicate a positive correlation between H2O adsorption levels and both fugacity and pore diameter. Furthermore, at constant pore diameter, the adsorption heat increases exponentially with increasing adsorption levels. Notably, H2O adsorption in LRC slit pores exhibits multilayer adsorption characteristics. First, adsorption occurs as monomolecular layers on the LRC surface, transitioning to secondary adsorption sites formed by previously adsorbed H2O molecules with increasing fugacity, ultimately saturating the pores. This adsorption process exhibits a correlation with a shift in potential energy distribution from high to low potential energy directions. Moreover, the ordering of H2O molecule arrangements between hydrogen atoms, oxygen atoms, and H2O molecules decreases with increasing pore diameters. Larger pore diameters correspond to increased H2O molecule diffusion, the stronger interaction between the LRC slit pores and H2O molecules but reduced interaction with individual H2O molecules. Overall, this study establishes a theoretical foundation for further studies on coal pore wetting and offer valuable insights for studies aimed at reducing dust and preventing gas outbursts.

Pt/GO/TiO2 room–temperature hydrogen sensing Schottky diode: High resistance to humidity interference endowed by the graphene oxide interlayer

Room–temperature hydrogen sensors usually suffer from dramatic response drop in humid air. Aiming to solve such issue of H2 sensing Schottky diodes, a platinum/graphene oxide/titanium dioxide (Pt/GO/TiO2) Schottky diode is designed. The GO interlayer between the 50–nm–thick Pt nanolayer and TiO2 substrate significantly improves resistance to humidity interference. Remarkably, the diode with a GO loading of 0.969 mg cm−2 exhibits a response retention rate (RRH95%/Rdry) of nearly 100%. To reveal the mechanism for the improved anti–humidity performance, the H2O adsorption behavior of Pt/GO/TiO2 diode was investigated by quartz crystal microbalance and near ambient pressure X–ray photoelectron spectroscopy. H2O molecules are absent on the Pt surface of Pt/GO/TiO2 in water vapor. This is a result of the H2O adsorption effect of the GO interlayer, which stems from the superior H2O adsorption ability of the GO interlayer and causes the diffusion of H2O molecules adsorbed on the Pt surface into the GO interlayer through nanochannels in the Pt nanolayer. Additionally, the GO interlayer serves as a blocking layer for the diffusion of hydroxyl species generated on the TiO2 surface to the Pt nanolayer. Such hydroxyl blocking effect prevents the consumption of adsorbed H atoms at the Pt/GO interface.

First-principles study on the effect of pressure on the adsorption of H2O on the Mg-montmorillonite (010) surface

The effect of pressure on H2O adsorption on the montmorillonite surface is a crucial issue in geomechanics and high-pressure physics. In this paper, the effect of pressure on adsorption capability were calculated based on density-functional theory (DFT) for pressures ranging from 0 to 18 GPa, and the adsorption energies and structures of the H2O molecules were analyzed with different surface coverages (0 < Θ ≤ 1.0 ML). Firstly, the clean (010) surface of Mg-montmorillonite was modelled at different pressures from an atomic perspective, then the calculations demonstrated that single H2O molecules were stably adsorbed on the top, bridge, hollow and interlayer bridge sites, independent of pressure. However, the adsorption energies at different sites were significantly influenced by the pressure and showed different trends. For the hollow and bridge sites, the adsorption energy increased within the pressure range 0–2 GPa but decreased within the pressure range 2–18 GPa. Conversely, for the top sites, the adsorption energy decreased with increasing pressure within the range 0–2 GPa but increased with increasing pressure within the range 2–18 GPa. For increasing coverage with H2O molecules, the adsorption energy was almost constant at 0 GPa but decreased within the range 0 < Θ ≤ 1.0 ML at 2, 10, and 18 GPa. Furthermore, the adsorption energies for the bridge sites all increased with increasing coverage but decreased with increasing coverage for the interlayer bridge sites at the four pressures. In addition, other characteristics of the H2O and Mg-montmorillonite (010) surface were discussed, including bonding, changes in the electronic density of states, the charge distribution, and the structure of the atomic interlayer at different pressures.

Interfacial strain induced crystalline-amorphous nanoarchitectures anchoring MoO42− anionic groups to alleviate self-discharge of battery-type cathodes

Battery-type cathodes that endow supercapacitors (SCs) with high energy density have severe self-discharge defect. However, the underlying origin and regulation strategy have never been reported. In this work, we proposed an advanced in-situ anionic group anchoring strategy utilizing the strain effect between external NCZ-LDH and internal NiMoO4. Combining experiments with theoretical calculation, we confirmed that the self-discharge behavior of battery-type cathodes is highly related with the dissociation reaction of H2O in fully charged state, while the defect can be significantly alleviated through the modification of MoO42− in the reconstructed strain induced crystalline-amorphous nanoarchitectures, which optimizes the adsorption and dissociation energies of H2O. As a result, the NiMoO4@NCZ-LDH electrode not only exhibits excellent capacity and durability, but also significantly increases capacity retention from 21.3 % to 79.7 % after self-discharge for 72 h and keeps in a high open circuit potential throughout. This study fills the blank of battery-type cathodes in self-discharge research and points out a promising direction for designing high performance SCs.

Bias stress stabilities of PMMA-passivated indium-gallium-zinc-oxide thin-film transistors after 100 °C steam exposure

Bias stress stabilities of the polymethyl methacrylate (PMMA)-passivated IGZO thin-film transistors (TFTs) after being exposed in a normal and harsh (100 °C steam) environment were studied, in order to comprehensively evaluate protection effects of PMMA. In a normal environment, the PMMA-passivated TFTs exhibited normal switching characteristics and electrical stabilities. However, the switching characteristics and bias stress stabilities were changed after being exposed on 100 °C steam. There were negative Vth shifts on the transfer curves of the steam-exposed IGZO TFTs. Our XPS analysis revealed that the negative ΔVth was related to the steam-induced H2O molecules throughout the IGZO films, which acted as electron donors to introduce more electrons in the front channel. Under PBS, the steam-exposed IGZO TFTs showed an abnormal negative Vth shift while the un-exposed IGZO TFTs showed negligible Vth shift. This abnormality was ascribed to the electrons released from steam-induced H2O molecules, which render the conductive path more easily opened. Under NBS, the steam-exposed IGZO TFT presented larger negative Vth shift than the un-exposed TFT. This result was interpreted in terms of the steam-induced donor states (H2O molecules) near or at channel/insulator interface. Under PBTS and NBTS, the changes in Vth for steam-exposed TFTs were similar to those for un-exposed TFTs. Such a similarity indicates that steam exposure had no effects on NBTS and PBTS stabilities. It was understood in terms that the steam-induced H2O+ recombined with the electrons released from the steam-induced H2O molecules under bias stress, forming H2O to compensate the thermally-induced H2O adsorption. Our results suggest that one-micron-thick PMMA passivation layer enabled to protect IGZO TFTs from H2O in a normal environment, but it provided inadequate protection in a harsh environment. Therefore, a thicker PMMA passivation layer should be considered.