Lewis Acid-base Interactions Research Articles

Novel Adsorption-Catalysis Design of CuO Impregnated CeO2 Nanorods As Cathode Modifier for Lithium-Sulfur Battery

Lithium sulfur batteries (LSBs) are a promising candidate to be used in modern commodities like electric vehicles, grid energy storage, electric aviation, and many others because of the exceptionally high theoretical capacity of sulfur (1675 mAh g-1), almost 5 times higher than the conventional lithium-ion batteries. However, the problem of polysulfide shuttling effect originating from the dissolved lithium polysulfides in the electrolyte results in poor cycling stability, hindering the commercialization of LSB. Significant advancement has been made over the years due to a great deal of research on novel materials development and structural design for lithium polysulfide (Li2Sn: 4≤ n ≤8) adsorption synergy to counter the polysulfide shuttling effect 1. However, rather than focusing only on the adsorption synergy (Physical confinement and chemical binding), novel catalysts that can accelerate the polysulfide conversion reaction kinetics are needed to design the next generation LSB. Previously, our group investigated shape-controlled cerium oxide (CeO2) to accelerate the polysulfide conversion reactions by generating the intermediate steps of thiosulfate and polythionate 2, 3. Copper oxide (CuO), being a p-type semiconducting material, is another promising material that can activate thiosulfate formation as its redox potential is 2.53 V vs Li/Li+, which lies in the potential window of 2.4 V < E° ≤ 3.05 V that selectively triggers the formation of thiosulfate. Herein, we investigated 10 wt% of CuO impregnated on the CeO2 nanorods (10 wt%CuO/CeO2) as a cathode host for LSB. The CuO impregnation on the surface of CeO2 nanorods attributed strong interaction between the surface defect rich CeO2 nanorods and the copper oxides (CuOx: Cu2O and CuO) promoting excellent electrocatalytic activity. The 10 wt%CuO/CeO2 sample provides adsorption-catalysis dual synergy to chemically bind and further catalyze the polysulfide conversion by polythionate and thiosulfate generation. As a result, the derived LSB exhibited excellent electrochemical performance with high capacity of 1141 mAh g-1 at 0.2 C with a sulfur loading of 1.33 mg cm-2 and a capacity loss of only 0.04% per cycle after 60 cycles. Key words: lithium sulfur batteries, lithium polysulfides, shuttle effect, cerium oxide, catalysis. Xiong, D. G.; Zhang, Z.; Huang, X. Y.; Huang, Y.; Yu, J.; Cai, J. X.; Yang, Z. Y., Boosting the polysulfide confinement in B/N–codoped hierarchically porous carbon nanosheets via Lewis acid–base interaction for stable Li–S batteries. Journal of Energy Chemistry 2020, 51, 90-100. Azam, S.; Wei, Z.; Wang, R., Cerium oxide nanorods anchored on carbon nanofibers derived from cellulose paper as effective interlayer for lithium sulfur battery. J Colloid Interface Sci 2022, 615, 417-431. Wei, Z.; Li, J.; Wang, R., Surface engineered polar CeO2-based cathode host materials for immobilizing lithium polysulfides in High-performance Li-S batteries. Applied Surface Science 2022, 580.

Simultaneous enrichment and sequential separation of glycopeptides and phosphopeptides with poly-histidine functionalized microspheres.

Protein phosphorylation and glycosylation coordinately regulate numerous complex biological processes. However, the main methods to simultaneously enrich them are based on the coordination interactions or Lewis acid-base interactions, which suffer from low coverage of target molecules due to strong intermolecular interactions. Here, we constructed a poly-histidine modified silica (SiO2@Poly-His) microspheres-based method for the simultaneous enrichment, sequential elution and analysis of phosphopeptides and glycopeptides. The SiO2@Poly-His microspheres driven by hydrophilic interactions and multiple hydrogen bonding interactions exhibited high selectivity and coverage for simultaneous enrichment of phosphopeptides and glycopeptides from 1,000 molar folds of bovine serum albumin interference. Furthermore, “on-line deglycosylation” strategy allows sequential elution of phosphopeptides and glycopeptides, protecting phosphopeptides from hydrolysis during deglycosylation and improving the coverage of phosphopeptides. The application of our established method to HT29 cell lysates resulted in a total of 1,601 identified glycopeptides and 694 identified phosphopeptides, which were 1.2-fold and 1.5-fold higher than those obtained from the co-elution strategy, respectively. The SiO2@Poly-His based simultaneous enrichment and sequential separation strategy might have great potential in co-analysis of PTMs-proteomics of biological and clinic samples.

A novel carbon adsorbent derived from iron-poisoned waste resin for phosphate removal from wastewater: Performance and mechanism

In this study, a new Fe-rich carbon composite derived from iron-poisoned waste resin (WRC) was successfully prepared via pyrolysis-activation to remove phosphate from wastewater. The physicochemical properties of WRC were characterized using multiple characterization tools. The results showed that the WRC had a large specific surface area and was rich in metal loading for adsorption. Batch and fixed-bed experiments investigated the adsorption performance of WRC. The maximum adsorption capacity calculated from the Langmuir model was 17.43 mg/g at 298 K. Kinetics experiments showed that the adsorption of phosphate by WRC accorded with pseudo-second-order kinetic model. The WRC could maintain excellent adsorption performance in a wide pH range of 2–12, suitable for various wastewater conditions. Meanwhile, the WRC had well anti-interference of common anions and humic acids on phosphate adsorption and WRC reuse performance. The mechanisms of phosphate adsorption by WRC were confirmed to be electrostatic attraction, ligand exchange and Lewis acid-base interaction. Fixed bed experiments were conducted for dynamic treatment of synthetic wastewater and actual wastewater, and the results indicated that WRC had potential application prospect. This study provides an economically feasible method for the phosphate removal from wastewater and achieves the reuse of waste resin.

Efficient CO2 adsorption on porous carbon with nitrogen functionalities based on polybenzoxazine: High-pressure adsorption characteristics

Ordered-interconnected porous carbon with nitrogen functionalities is a potential adsorbent for CO2 capture since it could adsorb CO2 gas through both physical and chemical mechanisms. Herein, we reported the preparation of ordered-interconnected porous carbons having nitrogen functionalities based on polybenzoxazine using a silica templating method. The CO2 adsorption measurement was performed at 30 °C and the pressure was varied from 1 to 40 bar. The results showed that the specific surface area (SSA) and pore volume showed a correlation trend indicating the increase with increasing silica templates up to 40 % and the carbon samples contained nitrogen functionalities on the surface (pyrrolic and pyridonic nitrogen, pyridinic nitrogen, and oxidized nitrogen). After CO2 activation, the nitrogen functionalities are still present on the surface of the porous carbon and the sample based on 40 wt% of silica (AC40%Si-800) exhibited the greatest SSA (1,391 m2/g) with extremely large pore volume (3.77 cm3/g). This led to the largest amount of CO2 uptake (25.07 mmol/g at 40 bar) recorded to date. For the first time, the computational study revealed that only pyridinic nitrogen (N-6) is capable of chemically adsorbing CO2 molecules via Lewis acid-base interaction, which synergistically enhanced the adsorption capability.

Multi-functionalization strategy for environmental monitoring: A metal-organic framework for high capacity Mercury(II) removal and exceptionally sensitive detection of nitroaromatics

The development of multifunctional metal-organic frameworks (MOFs) is a desirable method to use in different applications. As a new 3D MOF decorated with thiophene-urea functions, TMU-57 (formulated as [Zn(TDC)(DPU)].0.85DMF where H2TDC = thiophene-2,5-dicarboxylic acid, DPU = 1,3-di(pyridin-4-yl)urea), has been synthesized to improve the host-guest chemistry of the material. Since, TMU-57 is decorated with electron-rich thiophene and urea functions, it can interact through hydrogen bonding and Lewis acid-base interactions with different guests. In line with this approach, it is realized that TMU-57 is one of the most sensitive sensors to phenolic nitroaromatics (NACs), particularly 2,4,6-trinitrophenol, which reaches 92.5% (9) quenching at 5 ppb with Ksv value equal to 2 (1) × 10+8 M−1 and the detection limit of 9 × 10 −9 M (k = 3, σ = 0.6). Additionally, TMU-57 shows a high capacity for Hg(II) ions equal to 570 (14) mg.g−1. This work clearly shows that the multifunctionalization strategy can extend the application of functional MOFs as an efficient host from one to multiple applications.

Emerging Strategies for Gel Polymer Electrolytes with Improved Dual-Electrode Side Regulation Mechanisms for Lithium-Sulfur Batteries.

Although GPE still has the risk of shuttling due to the incomplete removal of liquid electrolytes compared to SPE, which has the most promise of eliminating polysulfide shuttling, researchers have made abundant efforts to eliminate as much of the polysulfide shuttling effect as possible while retaining the unique advantages of GPE. For example, physical barrier to polysulfides by improving the pore size of GPE or fabricating multidimensional structures by different preparation methods. Further chemical adsorption of polysulfides by adding nanofillers to increase polar sites to create polar-polar interactions with polysulfides or to create Lewis acid-base interactions. However, although chemical adsorption can indeed highly immobilize polysulfides, it still brings disadvantages such as loss of active material. Therefore, other researchers have employed GPE with ion-selective permeability that has electrostatic repulsive force or steric hindrance to polysulfides to better inhibit polysulfide shuttling. However, modifying only the cathode side is not enough to enhance this overall properties of Li-S cells. These problems of poor Li+ transport, lithium dendrite growth, and poor SEI due to uneven lithium ion deposit on Li anode side still affect the overall performance of Li-S cells. Therefore, a GPE to improve these problems on the Li anode side is summarized below. Compared with an all-solid electrolyte, GPE, which has a partially liquid electrolyte, clearly has advantages such as strong interfacial contact, good anode interface compatibility, and high flexibility. However, it is still not comparable to the ionic conductivity, etc. of pure liquid electrolyte only. Therefore, the problems on the lithium metal anode side are mainly focused on the lithium ion transport problems and the problems of lithium dendrite growth and inhomogeneous SEI at the lithium anode interface. Facing the problems in these two aspects, researchers have given many improvement solutions respectively. For the lithium ion transport problem, researchers have instead provided pathways for lithium ion transport by adding amorphous nanofibers or nanofillers to reduce the crystallinity of the polymer and improve the ionic conductivity. Alternatively, the migration number of lithium ions can be increased by limiting the anions in the electrolyte. As for the interfacial problems of lithium anodes, researchers have effectively suppressed the growth of lithium dendrites or inhomogeneous lithium plating/stripping phenomena mainly by adding nanofillers to increase the mechanical strength of GPE or by participating in the generation of SEI.

Borderline Metal Centers on Nonporous Metal-Organic FrameworkNanowire Boost Fast Li-Ion Interfacial Transport of Composite Polymer Electrolyte.

Metal-organic frameworks (MOFs) fillers are emerging for composite polymer electrolytes (CPEs). Enhancing Lewis acid-base interaction (LABI) among MOFs, polymer and Li-salt is expected to promote Li+ -transport. However, it is unclear how to customize a strong LABI interface. The large surface-area of classical MOFs also interferes with clarifying the LABI influence on Li+ -transport. Herein, Bi3+ as metal centers to design colloidal-dispersed nonporous MOFs (Bi/HMT-MOFs) nanowire with a surface-area of only 17.13 m2 g-1 to prepare polyethylene oxide (PEO)-based CPEs (BMCPE) is chosen. The nonporous feature can exclude the surface-area effect on Li+ -transport. More interestingly, Bi3+ is a typical borderline acid, which can interact with both hard-basic PEO and soft-basic Li-salt anion. Accordingly, Bi/HMT-MOFs are uniformly dispersed in the BMCPE to form a strong LABI interface with PEO and Li-salt, promoting Li-salt dissociation and providing rapid Li+ -transport channels. Despite the ultralow surface-area of Bi/HMT-MOFs, BMCPE exhibits significantly enhanced ion-conductivity and Li+ transference number, which completely rival traditional MOFs-filled CPEs. BMCPE also enables symmetric and full cells with excellent high-rate performance and long-term cycling stability. In contrast, when Bi3+ sites are obscured, electrochemical performances are obviously decreased. Therefore, employing borderline metal centers will be an effective strategy to construct a LABI interface for high-performance MOFs-filled CPEs.

Phosphate removal and recovery by lanthanum-based adsorbents: A review for current advances.

Controlling eutrophication and recovering phosphate from water bodies are hot issues in the 21st century. Adsorption is considered to be the best method for phosphate removal because of its high adsorption efficiency and fast removal rate. Among the many adsorbents, lanthanum (La)-based adsorbents have been paid more and more attention due to their strong affinity to phosphorus. This paper reviews research of phosphate adsorption on La-based adsorbents in different La forms, including lanthanum oxide/hydroxide, lanthanum mixed metal oxide/hydroxide, lanthanum carbonate, La3+, La-based metal-organic framework (La-MOF) and La-MOF derivatives. The La-based adsorbents can be loaded on many carriers, such as carbon material, clay minerals, porous silica, polymers, industrial wastes, and others. We find that lanthanum oxide/hydroxide and La3+ adsorbents are mostly studied, while those in the forms of lanthanum carbonate, La-MOF, and La-MOF derivatives are relatively few. The kinetic process of most phosphate adsorption is pseudo-second-order and the isotherm process is in accordance with the Langmuir model. The cost of La-based and other traditional adsorbents was compared. The adsorption mechanisms are categorized as electrostatic attraction, ligand exchange, Lewis acid-base interaction, ion exchange and surface precipitation. Besides, regeneration methods of La-based adsorbents are mainly acid, alkali, and salt-alkali. In addition, the La-based adsorbents after absorbing phosphate can be directly used as a slow-release fertilizer. This review provides a basis for the research on phosphate adsorption by La-based adsorbents. It should be carried out to further develop La-based materials with high adsorption capacity and good regeneration ability. Meanwhile, studies have been conducted on the reuse of phosphate after desorption, which needs more attention in future research.

Adsorption performance of one- and two-component anionic dyes using core-shell ZIF-8@ZIF-67

The discharge of dye wastewater threatens the ecology and biological health. Adsorption technology is the preferred treatment method and absorbent is core. In this study, a high-performance ZIF-8@ZIF-67 adsorbent was synthesized by epitaxial growth. XRD and TEM demonstrated the successful synthesis of the core-shell ZIF-8@ZIF-67 and BET showed that the specific surface area, pore volume and diameter of ZIF-8@ZIF-67 were 1518.75 ​m2/g, 0.65 ​cm3/g and 1.71 ​nm, respectively, with microporous being the predominant. The optimum adsorption conditions for the adsorption of Direct Blue-86 by ZIF-8@ZIF-67 were an initial concentration of 150 ​mg/g, a ZIF-8@ZIF-67 dosage of 5 ​mg, and a pH of 8, and the adsorption capacity at this condition was 301.69 ​mg/g. The mechanism of adsorption on Direct Blue-86 has been speculated to be electrostatic interaction, hydrogen bonding, Lewis acid-base interaction, π-π stacking and coordination. The kinetics of adsorption of Reactive Yellow and Congo Red in the two-component system were both consistent with the pseudo-second-order kinetic models, with chemisorption being the rate-controlling step and the adsorption rates of Reactive Yellow and Congo Red were both higher than that of one-component system. Meanwhile, they were more consistent with the Langmuir monolayer adsorption models, with maximum adsorption capacities of 261.10 ​mg/g and 291.55 ​mg/g, respectively, a decrease of 56.66% and 54.52% compared to that in the one-component system.

Effective passivation of perovkiste grain boundaries by a carboxylated polythoiphene for bright and stable Pure-Red perovskite light emitting diodes

High luminance and operative stability are essential parameters for realizing the commercialization of perovskite-based light-emitting diodes (PLEDs). However, the optoelectronic properties of PLEDs are still limited owing to the un-optimized charge transport behavior of perovskite films arising from severe defect densities and imperfect lattice structure at grain boundaries. To retrieve the morphological imperfection, we herein suggest a carboxylated polythiophene (P3CT) as a novel passivating agent of perovskite films in PLEDs. The carboxylic acid groups of P3CT enable Lewis acid-base interactions with the defective surface of perovskites such as under-coordinated Pb2+ sites or halide deficiencies, leading to efficient defect passivation and stabilization of the perovskite film surface. The P3CT-passivation successfully fabricates pinhole-free perovskite films with diminished defects at grain boundaries, bringing enhanced optoelectronic properties of red electroluminescence EL emission with a peak current efficiency and external quantum efficiency (EQE) values up to 11.15 % and 4 %, respectively. Moreover, the operative stability of the passivated PLEDs is markedly improved due to the stabilization and increased hydrophobicity of perovskite films by the inclusion of P3CT. The present findings provide a new perspective for developing stable red-PLEDs with efficient luminescence.

Enhanced performance of CsPbI2Br perovskite solar cell through improving the solubility of the components in precursor

As a key of the perovskite growth, the properties of precursor influence the quality of film greatly. Among many properties, the solubility of the solute determines whether crystal film can form or the film with high quality. Therefore, we chose the small organic molecule acetamide (AT) with functional groups NH2 and CO as additive to improve the solubility of the original component CsI and regulate the crystallization of CsPbI2Br perovskite. Different from the Lewis acid-base interaction occurred between the additives and PbI2 reported by many researches, the hydrogen bond formed between the NH2 in AT and the I in CsI in CsPbI2Br perovskite precursor improved the activity and solubility of CsI, the corresponding effects caused the components in precursor participated in the crystallization and stabilized the crystal structure. And which excellent addition reflected in the suppressed unstable δ phase generated during the crystallization. As a consequence, the Pb0 roots in halogen vacancies in control film was also eliminated after added the AT, and the nonstoichiometric ratio in annealed film was further eliminated. In final, the power conversion efficiency (PCE) increased from the 10.24 % for control solar cell to 13.36 % for modified solar cell, and the stability has also been greatly improved.

Assessing organic fouling of ultrafiltration membranes using partition coefficients of dissolved organic matter in aqueous two-phase systems

Organic fouling caused by dissolved organic matter (DOM) is a critical challenge for membrane technologies. In this study, prediction models for the fouling of commercial polyether sulfone (PES) and regenerated cellulose (RC) ultrafiltration membranes by DOM were established based on the hydrophobicity of DOM. The organic fouling behavior of 40 natural water samples collected from Lake Taihu was investigated. The fouling propensity of water samples on ultrafiltration membranes was evaluated using the fouling index (FI). The hydrophobicity of DOM in water samples was quantified by its partition coefficient in an aqueous two-phase system (KATPS). The FI of water samples on RC membranes was lower than that on PES membranes due to stronger repulsive Lewis acid-base interactions, which reduced DOM-membrane interactions. A significant positive correlation was found between KATPS and FI, suggesting the important role of DOM hydrophobicity in the organic fouling of ultrafiltration membranes. FI prediction models using KATPS as the variable were established using a training group containing 20 water samples for PES and RC membranes, respectively. The resulting models were then validated using the additional 20 water samples, which suggested good prediction power (RMSE = 1.65). The pH effect on the organic fouling can be adequately predicted by the same model with KATPS values measured at given pH. The results suggest that KATPS can be used as a convenient index for assessing the initial organic fouling of ultrafiltration membranes by freshwater DOM.

MgO coated magnetic Fe3O4@SiO2 nanoparticles with fast and efficient phosphorus removal performance and excellent pH stability

A regenerable MgO-coated magnetic Fe3O4@SiO2 (FSM) composite effectively avoided the agglomeration of nano-MgO, which was resoundingly used for efficient and rapid phosphorus removal from aqueous solutions. Based on an initial screening of synthesized FSM with different Mg/citric acid molar ratios in terms of phosphorus adsorption capacity, an FSM composite with a Mg-citric acid molar ratio of 1:1 (FSM-1:1) was determined as the optimal choice. Scanning electron microscope (SEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) showed that the prepared Fe3O4 was triumphantly loaded and the nano-MgO nanoparticles were evenly distributed on the surface of magnetic mesoporous silica. N2 adsorption-desorption experiments manifested that FSM-1:1 had a large specific surface area of 124.3 m2/g and the pore size distribution calculated based on the BJH model was centered at 9.36 nm. Furthermore, FSM-1:1 not only exhibited fast adsorption kinetics (60 min) but also had a high maximum theoretical adsorption capacity of 223.6 mg P/g, which was superior to all the other Mg-based adsorbents. Remarkably, due to the coating of MgO, FSM-1:1 exhibited ultra-high stability in the pH range of 3–11, a wider range than many other Mg-modified sorbents. Our adsorbents also showed excellent selectivity for phosphate anions even in the presence of various coexisting anions (e. g. NO3−, Cl− and SO42−) with varying ionic strengths (0.01 and 0.1 M), good recyclability, the removal rate of phosphate still reached 89.0% after three cycles. Electrostatic attraction, Lewis acid-base interaction and the ligand exchange between Mg–OH and phosphate anions were responsible for the phosphate adsorption mechanisms.

Polypyrrole complexation on biomass-derived powdered carbon for adsorptive elimination of emerging pharmaceutical contaminant Sulfamethoxazole: A comprehensive insight

Carbon-based adsorbents are a preferred class of adsorbents for eliminating an array of pollutants owing to their rigid porous morphology. However, the limitation of nitrogen-containing functional groups limits their applicability in targeting organic pollutants like antibiotic species. Such groups offer positively charged surfaces for the efficient adsorption of anionic antibiotic species. The current study aims to enrich the surface of the prepared biomass-derived powdered carbon (PC) with nitrogen-rich polymer viz. Polypyrrole (PPy) via in-situ oxidative polymerisation to prepare an N-enriched adsorbent (PPy-PC) for the adsorptive elimination of emerging antibiotic contaminant Sulfamethoxazole (SMX) from aqueous setups. Efficient adsorptive interactions between PPy-PC and SMX were reported at pH 6.0, owing to strong electrostatic interactions between anionic SMX species (pKa = 5.7) and cationic polypyrrole states viz. Polaron (PPy+.) and bi-polaron (PPy++) state. Other interactions, viz. π-π electron donor-acceptor (EDA) interaction, hydrogen bonding, Lewis acid-base interaction, charge-assisted hydrogen bonding (CAHB) etc., also contributed to the adsorptive interactions. Isotherm model studies verified good fitting of both Freundlich and Langmuir isotherm models with the experimental data, verifying the possibility of multilayer and monolayer fashion of SMX's adsorption on PPy-PC. Elevating ionic strength of the SMX medium showed a slight decline in its adsorption capacity. Co-existing heavy metals had little effect on SMX's adsorption, whereas co-existing antibiotics significantly affected SMX's adsorption over the PPy-AC surface. Desorption and re-adsorption analysis verified the recyclability potential of the adsorbent for multiple cycles. Seed toxicity studies using Vigna mungo seeds verified the adsorbent's efficacy in remediating SMX solution. Continuous column studies verified lower column bed heights (cm), higher inlet feed concentrations (mg/L), and higher initial feed flow rates (mL/min) resorted to quick saturation of the packed bed column.

Enhanced defluoridation in household filter using binary metal hydrochar composite

Elevated fluoride concentration in water can trigger several health-related problems. In this study, the influence of post pyrolysis hydrothermal activation on defluoridation has been investigated to check their interacting effect using response surface methodology. Amongst the various optimizing factors which were investigated, temperature and time emerged as the most significant factors (p-value < 0.05). The Fe–Zn (2:1) binary metal hydrochar composite synthesized from optimized hydrochar demonstrated an optimum dose, contact time, initial concentration and solution pH of 0.8 g/L, 120 min, 5 mg/L and 7 respectively. The isotherm and kinetic results indicated that experimental data best fitted to Langmuir and pseudo-second order, with a determination coefficient approaching one (R2 = 0.99). Maximum monolayer adsorption capacity for this composite was found to be 28.41 mg/g. Thermodynamic parameters corroborate that defluoridation was chemisorption in nature (ΔH⁰ >10 kJ/mol) and was favoured at lower temperature (30 °C). An extensive characterization was employed to explain the adsorption mechanism, and confirmed occurrence of Lewis acid-base interactions, ion-exchange processes and electrostatic interactions. The performance of a fixed bed column was assessed based on breakthrough curve analysis. This novel composite could therefore serve as an efficient fluoride adsorbent because of enhanced sorption at neutral pH and reusability, thereby ensuring a sustainable and practical solution for low-cost defluoridation of drinking water.

Valorization of orange peel waste to tunable heteroatom-doped hydrochar-derived microporous carbons for selective CO2 adsorption and separation

Constrained by the extortionately expensive carbon sources, low carbon yields, inadequate adsorption capacities, and corrosive chemical activating agents, the commercialization of carbonaceous CO2 adsorbents remains a challenging task. Herein, potassium oxalate (K2C2O4), an activating agent with less corrosive properties, was used for the synthesis of activated carbons from inexhaustibly available “orange peel biowaste.” For the first time, a comprehensive report is presented on the effect of hydrothermal treatment, hydrochar/K2C2O4 ratio, activation temperature, and melamine modification in tailoring the porosity and surface functionalization of activated carbons. The optimized sample, OPMK-900, exhibited large specific surface area ~2130 m2/g; micropore volume ~1.1166 cm3/g, and a high pyrrolic nitrogen content (~ 46.1 %). Notably, melamine played the dual role as a promoter to K2C2O4 porosity generation and a nitrogen dopant, which synergistically led to an efficient CO2 uptake of ~6.67 mmol/g at 273 K/ 1 bar via micropore-filling mechanism and Lewis acid–base interactions. Moreover, remarkably high IAST CO2/N2 selectivity (105 at 273 K and 96 at 298 K) surpasses most of the biomass-derived carbons. Furthermore, the moderately high isosteric heat of adsorption (∆Hads ~ 38.9 kJ/mol) revealed the physisorption mechanism of adsorption with a limited energy requirement for the regeneration of the spent adsorbents.

Regulating Competitive Doping in Solution‐Mixed Conjugated Polymers for Dramatically Improving Thermoelectric Properties

AbstractLargely soluble tris(pentafluorophenyl)borane (BCF) has recently emerged as a promising molecular dopant for preparing highly conductive organic thermoelectrics (TEs) using a one‐step solution‐mixing method. However, the unique doping mechanisms that include both undesirable Lewis acid doping with BCF and effective Brønsted acid doping with BCF–water complexes limit its widespread applications. Herein, the feasibility of modulating the two doping mechanisms by utilizing the competitive Lewis acid–base interactions of BCF with H2O or Lewis basic groups in conjugated polymers is demonstrated. The polymer without strong Lewis basic groups undergoes Brønsted acid doping, which efficiently forms delocalized free charge carriers and leads to superior TE power factors and figures of merit of 49.6 µW m−1 K−2 and 0.061, respectively. However, the polymer with strong Lewis basic groups undergoes both doping mechanisms competitively. BCF–polymer Lewis complexes not only generate free charge carriers inefficiently, but also hinder possible Brønsted acid doping and localize charge carriers, significantly lowering the TE properties. Nevertheless, the reduced TE properties can be dramatically improved by thermally annealing the predoped polymer films because Lewis acid doping can be substantially replaced by Brønsted acid doping owing to the different thermal stabilities between the BCF–polymer and BCF–water complexes.

Stable and recyclable polyporous polyurethane foam highly loaded with UIO-66-NH2 nanoparticles for removal of Cr(Ⅵ) in wastewater

Efficient and recoverable adsorption technology plays a key role in removing the heavy metal Cr(Ⅵ) from wastewater. The metal-organic frameworks (MOFs) are very unstable in aqueous solution and their structure is easy to be destroyed. Of all MOFs, UIO-66-NH 2 (Zr-MOF) is widely used to adsorb heavy metal ions in wastewater. But UIO-66-NH 2 has disadvantages of small size and easy aggregation. When it is employed as the absorbent of industrial wastewater, it is impossible to be recycled after absorption. Therefore, in this study taking advantage of the excellent properties of polyurethane foam (PUF) such as porous network, light weight and abundant binding sites, UIO-66-NH 2 were loaded on PUF by in-situ growth method to obtain a composite UIO-66-NH 2 @PUF. BET and MIR results confirmed the co-existence of macropore, micropore and mesopore. The absorption kinetics and isotherms indicated that the adsorption capacity of UIO-66-NH 2 @PUF to Cr(Ⅵ) was 92 mg/g and Langmuir model could better describe adsorption process, as well as the process belongs to monolayer adsorption. After six cycles, the removal rate of UIO-66-NH 2 @PUF still reached to 79%. XRD, EDS and determination result of Zr(Ⅳ) concentration showed that the exfoliation of Zr(Ⅳ) was negligible, which proved UIO-66-NH 2 @PUF had excellent chemical stability after repeated use. The adsorption mechanism was the comprehensive effect of ligand exchange and Lewis acid-base interaction between Zr(Ⅳ) and Cr(Ⅵ) which was concluded by XPS. Owing to these attributes, loading MOFs powder on porous carrier makes it possible to reuse MOFs and avoid secondary pollution.

Surface passivation of perovskite films by potassium bis(fluorosulfonyl)imide for efficient solar cells

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted much attention because of their high photoelectric conversion efficiency (PCE) and simple preparation process. At present, one of the major factors limiting the further improvement of PSCs’ performance is defects in perovskite active layers. Herein, we report an effective surface post-treatment method for perovskite active layers, which uses potassium bis(fluorosulfonyl)imide (KFSI) to passivate multiple defects, improve photovoltaic performance and reduce the hysteresis. It is demonstrated that not only S=O and S–N bonds but also charged K + and FSI − ions in KFSI contribute to the passivation of multiple defects in perovskite films via Lewis acid-base interaction and/or forming ionic bonds. After the optimized KFSI treatment, the trap density of the perovskite film decreased from 8.41 × 10 15 cm −3 to 3.97 × 10 15 cm −3 , which significantly suppressed trap-assisted nonradiative recombination of carriers in perovskite films and/or at perovskite/hole transport layer interface. The KFSI treated device achieved a PCE of ∼19.00% with less hysteresis, appreciably outperforming the control device (17.22%). At the same time, the performance reproducibility among the fabricated solar cells was remarkably improved. This work provides a facile way to passivate multiple defects in perovskite films and further enhance the performance of perovskite solar cells. • An effective passivator - potassium bis(fluorosulfonyl)imide (KFSI) for passivating multiple perovskite defects is reported. • Not only S=O and S–N bonds but also charged K + and FSI − ions in KFSI contribute to the passivation of multiple defects. • After the optimized KFSI treatment, the trap density decreased, which suppressed non-radiative recombination of carriers. • The KFSI treated device appreciably outperforms the control device in terms of efficiency, hysteresis and reproducibility.

Effects of the same valence metal cations on the aggregation behavior of PFR

In recent years, phenol-formaldehyde resin (PFR) as a colloid plugging agent was extensively used in enhanced oil recovery. It has been popularly concerned that the influence of environment on the structure, migration and aggregation behavior of PFR. The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory can explain the interaction potential between particles. However, the classical DLVO cannot explain differences when colloids aggregate in the same valence metal cation solution. In this work, the effects of ion specificity of divalent metal cations (i. e., Mg2 + and Ca2 +) on the aggregation rate, fractal dimension, zeta potential and the critical coagulation concentration (CCC) of PFR were systematically studied by dynamic light scattering experiment, electrophoretic light scattering and spectral turbidimetry. The experimental results showed that metal cations with poor hydration (i. e., Mg2 +) can promote aggregation more than metal cations with good hydration (i. e., Ca2 +). The hydrated differences of ions can be explained quantitatively by the improved DLVO theory introducing Lewis acid-base interaction. This result revealed the important significance of ion specificity in the aggregation behavior of PFR colloids, and made it possible to understand the co-transport process of PFR aggregates and metal cations in reservoirs. Thus, it is possible to precisely control the aggregation rate and the fractal dimension of PFR aggregates.