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HighlightsAlternating positively and negatively charged surface controlled by pH expedites and homogenizes Zn2+ flux, endowing the Zn- silk fibroin (SF) anode with low polarization voltage and stable stripping/plating.Experimental analyses with theoretical calculations suggest that SF coating facilitates the desolvation of [Zn(H2O)6]2+ and provides nucleation sites for uniform deposition.Symmetric battery of Zn–SF anodes delivers high-rate performance (up to 20 mA cm−2) and excellent stability (1500 h at 1 mA cm−2; 500 h at 10 mA cm−2) with cumulative capacity of 2.5 Ah cm−2.Metallic interface engineering is a promising strategy to stabilize Zn anode via promoting Zn2+ uniform deposition. However, strong interactions between the coating and Zn2+ and sluggish transport of Zn2+ lead to high anodic polarization. Here, we present a bio-inspired silk fibroin (SF) coating with amphoteric charges to construct an interface reversible electric field, which manipulates the transfer kinetics of Zn2+ and reduces anodic polarization. The alternating positively and negatively charged surface as a build-in driving force can expedite and homogenize Zn2+ flux via the interplay between the charged coating and adsorbed ions, endowing the Zn-SF anode with low polarization voltage and stable plating/stripping. Experimental analyses with theoretical calculations suggest that SF can facilitate the desolvation of [Zn(H2O)6]2+ and provide nucleation sites for uniform deposition. Consequently, the Zn-SF anode delivers a high-rate performance with low voltage polarization (83 mV at 20 mA cm−2) and excellent stability (1500 h at 1 mA cm−2; 500 h at 10 mA cm−2), realizing exceptional cumulative capacity of 2.5 Ah cm−2. The full cell coupled with ZnxV2O5·nH2O (ZnVO) cathode achieves specific energy of ~ 270.5/150.6 Wh kg−1 (at 0.5/10 A g−1) with ~ 99.8% Coulombic efficiency and retains ~ 80.3% (at 5.0 A g−1) after 3000 cycles.

The recognition of the surface reconstruction of the catalysts during electrochemical CO2 reduction (CO2RR) is essential for exploring and comprehending active sites. Although the superior performance of Cu–Zn bimetallic sites toward multicarbon C2+ products has been established, the dynamic surface reconstruction has not been fully understood. Herein, Zn-doped Cu2O nano-octahedrons are used to investigate the effect of the dynamic stability by the leaching and redeposition on CO2RR. Correlative characterizations confirm the Zn leaching from Zn-doped Cu2O, which is redeposited at the surface of the catalysts, leading to dynamic stability and abundant Cu–Zn bimetallic sites at the surface. The reconstructed Zn-doped Cu2O catalysts achieve a high Faradaic efficiency (FE) of C2+ products (77% at –1.1 V versus reversible hydrogen electrode (RHE)). Additionally, similar dynamic stability is also discovered in Al-doped Cu2O for CO2RR, proving its universality in amphoteric metal-doped catalysts. Mechanism analyses reveal that the OHC–CHO pathway can be the C–C coupling processes on bare Cu2O and Zn-doped Cu2O, and the introduction of Zn to Cu can efficiently lower the energy barrier for CO2RR to C2H4. This research provides profound insight into unraveling surface dynamic reconstruction of amphoteric metal-containing electrocatalysts and can guide rational design of the high-performance electrocatalysts for CO2RR.

Treating water pollution, especially dye-contaminated wastewater, in an economical and efficient manner remains a challenge as the surface charge diversity of contaminants. This work designed a nanocellulose-based amphoteric adsorbent based on 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) with in situ polymerization of diallyl dimethyl ammonium chloride (PDMDAAC). To explore the adsorption capacity of the amphoteric adsorbent (TOCN/PDMDAAC) for negatively and positively charged contaminants, methyl orange (MO, an anionic dye) and methylene blue (MB, a cationic dye) were employed as adsorbates. The effect of adsorbent on the adsorption performance at different pH, initial concentration of dye, contact time and ionic strength were investigated by batch treatment method. Equilibrium isotherms, kinetics and thermodynamics of dyes onto TOCN/PDMDAAC were examined, which implied that the adsorption behavior was monolayer and the adsorption process was spontaneous endothermic. The adsorption mechanisms are hydrogen bonding and electrostatic interactions between the dye and the active site on the adsorbent. The adsorption behavior of the binary blended dye system of MO and MB has also been investigated, and the addition of the other dye of higher concentration showed a synergistic adsorption behavior. According to the Langmuir model, at pH 7, 298 K, the equilibrium adsorption of MO and MB onto TOCN/PDMDAAC was as high as 404.86 mg g−1 and 520.83 mg g−1, respectively. These results indicated that TOCN/PDMDAAC was an effective amphoteric adsorbent, which offered a promising strategy for the adsorption of multicomponent dyes in an eco-friendly way.Graphic Abstract

Strategies followed to improve SBA-15 surface (essentially inert) included modifications by adding acidic or basic (or both) species during or after silica synthesis. Amphoteric properties are especially important, as some reactions (alcohol dehydration, for instance) require both types of sites to efficiently take place. In this work, single Zr (nominal 3, 5, and 10 wt%, as ZrOCl2•8H2O) direct addition during SBA-15 synthesis was used to impart amphoteric characteristics (as determined by NH3 and CO2 TPD) to mesostructured SiO2 matrices. Additional materials characterization included textural (N2 physisorption) and structural (XRD, FTIR, and UV–Vis spectroscopies, and HRTEM as well) studies. Actual solids composition was also determined (EDS). The degree of Zr incorporation into mesoporous silica was enhanced with nominal content in binary formulations, although not necessarily integrated into SBA-15 walls forming Zr-O-Si linkages. It seemed that single ZrO2 domains (framework and extra-framework) could provide suitable amphoteric properties by significantly increasing the number and strength of both acid and basic sites (especially formulations containing nominal 5 wt% Zr), as to those over mesostructured silica matrices. Also, potentially deleterious strong acid sites were avoided. The binary oxides present great potential to be applied in reactions requiring vicinal acid–base pairs (alcohol dehydration, for instance).

Leather wastewater harms the ecological environment and human health. In this study, a modified bio-flocculant was prepared to facilitate treatment of leather wastewater. A bio-flocculant produced by Bacillus cereus was combined with amphoteric starch and modified using a cerium ammonium nitrate initiator. Single factor optimization and orthogonal optimization were used to determine the optimal preparation conditions as follows: amphoteric starch-to-flocculant ratio = 22:30; reaction temperature = 64 °C; initiator dosage = 2.00%; reaction time = 15 min; stirring speed = 600 rpm; and flocculation system pH = 8.0. At a dosage of 1 g/L added to simulated leather industry wastewater, the flocculation efficiency (98.17%) and the total nitrogen removal efficiency (100.00%) of modified bio-flocculant was superior to that achieved by 1 g/L of unmodified bio-flocculant (72.16% and 50.00%, respectively), amphoteric starch (8.50% and 0.00%) and polyacrylamide (95.55% and 75.00%). Analysis of natural and flocculated precipitates in the wastewater showed that the modified bio-flocculant significantly changed several characteristics of the flocculated particles; in addition, it promoted the removal of nitrogenous substances in the process of denitrification. These changes helped explain the material's flocculating ability. The results confirmed that the modified bio-flocculant was an effective additive for treating leather wastewater.

To evaluate thermal properties and promote the application of novel N -oxide amphoteric energetic compound 4,6-diamino-3-hydroxy-2-oxo-2,3-dihydro-1,3,5-triazine-1-oxide (DAOTO), thermal behaviors of DAOTO were studied systematically by differential scanning calorimeter (DSC), thermogravimetric analyzer (TG/DTG) and thermogravimetric-mass-infrared spectrometry (TG-MS-FTIR) techniques. Results showed that DAOTO has only an obvious exothermic decomposition process during the range of 250 ~ 350 °C with an extrapolated starting point temperature ( T e ) of 291.6 °C, a peak temperature ( T p ) of 320.6 °C, a heat release of 1317 J g −1 and a corresponding mass loss of ~ 17%, at a heating rate of 10 °C min −1 , and the kinetic equation of thermal decomposition process was obtained. The main thermal decomposition gas products of DAOTO are H 2 O, NH 3 and CO, and the possible thermal decomposition process was analyzed. Besides, the specific heat capacity of DAOTO at 298.15 K was determined as 1.14 J g −1  K −1 , and adiabatic time-to-explosion was calculated to be a certain value between 100 and 105 s. This work proved DAOTO having a good thermal stability and provided theoretical support for the application of DAOTO.

Amphoteric PSF(polysulfone)-g-NaPSS(sodium p-styrene sulfonate)/PVP (polyvinylpyrrolidone) blended ion exchange membranes were prepared by simple solution casting method with dimethyl sulfoxide (DMSO) as solvent. The effect of the ratio of PSF-g-NaPSS to PVP on the properties of the membranes were studied and compared to that of Nafion 115 (DuPont). The results proved that when the mass ratio of PSF-g-NaPSS to PVP was 3:7 (M 3:7 ), the prepared membrane has exhibited the highest ion selectivity. As a result, the VRB single cell with M 3:7 was superior to that of Nafion 115 under the same condition. Furthermore, after 300 charge-discharge cycles, the efficiency of the M 3:7 membrane has no obvious decrease, and the static chemical stability test reveals that the mass loss ratio and vanadium ion permeability loss ratio of the M 3:7 are only slightly higher than that of N 115 membrane. Consequently, the prepared PSF-g-NaPSS/PVP amphoteric membrane is one of promising candidates for VRB application.

The main challenge in using Zeolit Alam Lampung (ZAL) as a catalyst lies in controlling its acidic nature which is influenced by the content of alkali metals, alkaline earth metals, transition metals, and Si/Al ratio. Controlling by reducing and adding metals with higher acidity is necessary. This research involved two stages: ZAL Swelling formation followed by adding Cu, Ni, and Fe metals to make a Cu-Ni-Fe/ZAL Swelling catalyst. The acid distribution analysis using the NH3-TPD profile test showed that the Cu-Ni-Fe/ZAL swelling catalyst exhibited higher Lewis-type acidity and more uniform distribution compared to Brønsted acid. The addition of Cu, Ni, and Fe metals can modify the acidity strength of ZAL Swelling to form Cu-Ni-Fe/ZAL Swelling catalysts with Lewis and Brønsted sites at lower temperatures (120–550 °C) compared to ZAL Swelling (120–750 °C). This gives an idea about the optimization of the arrangement of Lewis and Bronsted acid sites to present amphoteric features.

AlGaN alloys with high Al content offer the possibility to create deep ultraviolet light sources emitting at wavelengths ≤ 240 nm with enhanced quantum efficiency. However, increasing the band gap when the Al content surpasses  ~80% leads to problems with n -type doping of AlGaN alloys with the standard choice of Si donors, due to the formation of the so-called negative Si DX center. In this paper, we show that the amphoteric nature of the Si dopant in AlGaN alloys is fundamentally controlled by the local environment and the ordering of the Ga and Al atoms in the vicinity of the Si atom. Our conclusions are based on advanced characterization sensitive to the local environment of defects and impurities, complemented by electronic structure calculations. We propose that spatial ordering of Ga and Si atoms could allow efficient n -type doping at even higher Al contents, including AlN. The authors show that the amphoteric nature of the Si dopant that prevents efficient n -type doping in high Al-content AlGaN alloys is controlled by the ordering of the Ga and Al atoms in the immediate surroundings of the Si atom.

As oil and gas exploration advances, the development of deep, low-permeability, high-temperature, and high-salinity reservoirs poses increasing challenges. To address this, a novel amphoteric surfactant (TASS) was synthesized via free radical polymerization, and a high-performance water-based fracturing fluid system was developed. The system exhibited excellent thermal and salt resistance, with viscosity decreasing by less than 3.3% after 72 h at 150 °C and 20 wt% NaCl. It demonstrated clear shear-thinning behavior and strong elasticity. Interfacial activity tests showed that increasing NaCl concentrations reduced interfacial tension from 28.5 to 24.3 mN/m, while the contact angle on sandstone surfaces decreased significantly, indicating enhanced wettability and oil flow. Field applications further confirmed its effectiveness, with oil and gas production increasing by 81% and 133%, respectively, and a payback period of around 10 days. These results highlight the TASS fracturing fluid as a promising solution for stimulation in complex reservoirs. Unlike conventional betaine-type VES, the silane-grafted amphoteric design of TASS ensures viscosity retention at 220 °C and 25 wt% salinity.