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The release of wastewaters containing relatively low levels of nitrate (NO₃⁻) results in sufficient contamination to induce harmful algal blooms and to elevate drinking water NO₃⁻ concentrations to potentially hazardous levels. In particular, the facile triggering of algal blooms by ultra-low concentrations of NO₃⁻ necessitates the development of efficient methods for NO₃⁻ destruction. However, promising electrochemical methods suffer from weak mass transport under low reactant concentrations, resulting in long treatment times (on the order of hours) for complete NO₃⁻ destruction. In this study, we present flow-through electrofiltration via an electrified membrane incorporating nonprecious metal single-atom catalysts for NO₃⁻ reduction activity enhancement and selectivity modification, achieving near-complete removal of ultra-low concentration NO₃⁻ (10 mg-N L−1) with a residence time of only a few seconds (10 s). By anchoring Cu single atoms supported on N-doped carbon in a carbon nanotube interwoven framework, we fabricate a free-standing carbonaceous membrane featuring high conductivity, permeability, and flexibility. The membrane achieves over 97% NO₃⁻ removal with high N₂ selectivity of 86% in a single-pass electrofiltration, which is a significant improvement over flow-by operation (30% NO₃⁻ removal with 7% N₂ selectivity). This high NO₃⁻ reduction performance is attributed to the greater adsorption and transport of nitric oxide under high molecular collision frequency coupled with a balanced supply of atomic hydrogen through H₂ dissociation during electrofiltration. Overall, our findings provide a paradigm of applying a flow-through electrified membrane incorporating single-atom catalysts to improve the rate and selectivity of NO₃⁻ reduction for efficient water purification.

Electrochemical CO 2 reduction reaction (CO 2 RR) has been regarded as one of the most promising solutions to achieving “zero carbon emission”. In most of the CO 2 RR-related studies, high-purity CO 2 has been employed as the feed gas; however, in practice, CO 2 is generally emitted in low concentrations, so it is of great significance to realize high-selectivity electroreduction of low-concentration CO 2 with large concentration fluctuation. In this work, we constructed a dual-active-site catalyst and successfully achieved CO 2 local enrichment and conversion for low-concentration CO 2 . Operando experiments reveal that the catalyst has one type of site for activating CO 2 and one type of site for binding the reaction intermediates. The dual-active-site catalyst displays a selectivity for formic acid consistently above 97% over a broad potential window (from −0.9 to −1.6 V vs. RHE). Even when fed with a low-concentration CO 2 stream (volume ratio from 50% down to 10%), the dual-active-site catalyst could display high activity and selectivity (>91%). In particular, the selectivity is still above 85% when the CO 2 volume ratio is as low as 5%. This work offers a feasible route for converting low-concentration CO 2 via a synergistic effect for dual-active-site catalysts.

Unraveling atomic‐level active sites of layered photocatalyst towards low‐concentration CO2 conversion is still challenging. Herein, the yield and selectivity of photocatalytic CO2 reduction of the Aurivillius‐related oxide semiconductor Bi2O2SiO3 nanosheet (BOSO) were largely improved using a surface sulfidation strategy. The experiment and theoretical calculation confirmed that surface sulfidation of the Bi2O2SiO3 nanosheet (S‐BOSO, 6.28 nm) redistributed the charge‐enriched Bi sites, extended the solar spectrum absorption to the whole visible range, and considerably enhanced the charge separation, in addition to creating new reaction active sites, as compared to pristine BOSO. Subsequently, surface sulfidation played a switchable role, wherein S‐BOSO showed a very high CH3OH generation rate (12.78 µmol g−1 for 4 h, 78.6% selectivity) from low‐concentration CO2 (1000 ppm) under visible light irradiation, which outperforms most of the state‐of‐the‐art photocatalysts under similar conditions. This study presents an atomic‐level modification protocol for engineering reactive sites and charge behaviors to promote solar‐to‐energy conversion. A desirable atomic‐level sulfidation strategy over an Aurivillius‐related layer‐structured photocatalyst Bi2O2SiO3 is demonstrated. Sulfidation‐induced reactive sites facilitate local charge separation, contributing to enhanced low‐concentration CO2 photoreduction. The system also shows feasibility in diluted CO2 conditions, typically hindered by the deficient reactive sites in conventional systems.

Rechargeable aqueous zinc‐ion batteries (ZIBs) have been considered as a promising candidate for the large‐scale energy storage device owing to their low cost and high safety. However, the practical application of aqueous ZIBs at low temperature environment is hindered by the freezing aqueous electrolytes, which leads to a sharp drop in ionic conductivity, and thereby a rapid deterioration of battery performance. Herein, a chaotropic salt electrolyte based on low concentration aqueous Zn(ClO4)2 with superior ionic conductivity under low temperature (4.23 mS/cm at −50°C) is reported. The anti‐freezing methodology introduced here is completely different from conventional freeze‐resistant design of using “water‐in‐salt” electrolyte, cosolvents, or anti‐freezing agent additives strategy. Experimental analysis and molecular dynamics simulations reveal that the as‐prepared Zn(ClO4)2 electrolyte possesses faster ionic migration compared with other commonly used Zn‐based salts (i.e., Zn(CF3SO3)2 and ZnSO4) electrolyte. It is found that Zn(ClO4)2 electrolyte can suppress the ice crystal construction by forming more hydrogen bonds between solute ClO4− and solvent H2O molecules, thus leading to a superior anti‐freezing property. The fabricated ZIBs using this aqueous electrolyte exhibits a dramatically enhanced specific capacity, remarkable rate capability, and great cycling stability over a wide temperature range, from −50 to 25°C. The aqueous ZIBs also exhibit an outstanding energy density of 238.4 Wh/kg without compromising the power density (7.9 kW/kg) under −20°C. Moreover, the assembled aqueous ZIBs can also cycle stably over 1000 cycles at an ultra‐low −50°C. The high‐safety and cost‐effective chaotropic salt electrolyte presented here is a promising strategy for low temperature energy storage application. A cost‐effective, anti‐freezing, and high ionic conductivity Zn(ClO4)2 chaotropic salt electrolyte is discovered and applied in low‐temperature aqueous zinc‐ion battery.

In this paper, molecularly imprinted Zr-doped TiO 2 photocatalysts (MIP-ZrO 2 -TiO 2 ) were prepared by the molecularly imprinted sol–gel method for the photocatalytic degradation study of hydroquinone (HQ) as the target pollutant. For the effectiveness of the MIP-ZrO 2 -TiO 2 catalyst in degrading HQ, the effects of Zr doping ratio, imprinted molecule dosage, calcination conditions, and pollutant concentration on its photocatalytic activity were investigated. XRD, TEM, XPS, and other techniques were used to evaluate the materials, and the findings revealed that MIP-ZrO 2 -TiO 2 films with imprinted HQ were successfully produced on the ZrO 2 -TiO 2 surface. The optimal preparation conditions were n(Ti):n(Zr) = 100:8, m(HQ) = 1.5 g, 550 °C for the calcination temperature, and 2 h for the calcination duration. The optimum reaction conditions were 10 mg/L HQ concentration, 1 g/L catalyst dose, and a pH of 6.91. According to the findings of photocatalytic tests, during 30 min of UV lamp (365 nm) irradiation, the degradation rates of MIP-ZrO 2 -TiO 2 , ZrO 2 -TiO 2 , and TiO 2 for HQ were 90.58%, 83.94%, and 58.30%, respectively. The findings revealed that the doping of Zr metal and the addition of imprinted molecules improved the photocatalytic activity of TiO 2 , which can be used for the efficient treatment of low concentrations of hard-to-degrade hydroquinone.

Gold nanobipyramids (GNBPs) have garnered significant attention for photothermal therapy owing to their excellent photothermal conversion efficiency. Although the traditional surfactant cetyltrimethylammonium bromide (CTAB) effectively controls the morphology of gold nanomaterials, the cytotoxicity associated with its high concentration severely limits its biomedical application. In this study, four quaternary ammonium salt surfactants with bulkier headgroups were innovatively designed to synthesize GNBPs. For the synthesis of GNBPs, these novel surfactants require only very low concentrations (0.008–0.015 M), which are 6.7 to 12.5 times lower than the typical CTAB concentration used (0.1 M). The effects of surfactant concentration and solution pH on GNBPs synthesis were systematically investigated using a seed-mediated growth method. The results indicated that the optimal concentration and pH for GNBPs synthesis differed among the four surfactants, and possible reasons for this were proposed. These novel surfactants enabled the synthesis of GNBPs with high aspect ratios and absorption maxima between 800–850 nm at low concentrations. Furthermore, the use of extremely low concentrations significantly reduced the cytotoxicity of the surfactant residue. Future research will involve a comprehensive investigation into the photothermal conversion efficiency (PTE) of GNBPs fabricated with our novel surfactants, with direct comparisons to CTAB-synthesized counterparts. This work provides a superior alternative for the application of GNBPs in biomedicine and opens new prospects for the use of other extended surfactants for the synthesis of Au nanomaterials.

The solvent‐rich solvent sheath in low‐concentration electrolytes (LCEs) not only results in high desolvation energy of Li+, but also forms organic‐rich solid electrolyte interface film (SEI) with poor Li+ conductivity, which hinders Li+ transport at the electrode‐electrolyte interface and greatly limits the application of LCEs. Here, the electrochemical performance of the LCEs is enhanced by dual interfacial modification with LiNO3 and vinylene carbonate (VC) additives. Results show that LiNO3 is preferentially reduced at about 1.65 V to form an inorganic‐rich but incomplete SEI inner layer. The formation of Li3N and LiNxOy inorganic components helps to achieve rapid Li+ transport in the SEI film, and the bare electrode surface caused by the incomplete SEI inner layer provides a place for the subsequent decomposition of VC. Then, at a lower potential of about 0.73 V, VC is reduced to generate the poly(VC)‐rich SEI outer layer, which provides lithium‐philic sites and greatly weakens the interaction between Li+ and ethylene carbonate (EC). The interaction modulates the Li+ solvation structure at the interface and reduces the desolvation energy of Li+. This ingenious design of the bilayer SEI film greatly enhances Li+ transport and inhibits the decomposition of traditional carbonate solvents and the swelling of graphite. As a result, the electrochemical performance of the battery using 0.5 M LiPF6 EC/diethyl carbonate (DEC) + 0.012 M LiNO3 + 0.5 vt% VC is improved to a higher level than the one using 1.0 M LiPF6 EC/DEC electrolyte. This research expands the design strategy and promising applications of LCEs by constructing a favorable SEI to enhance Li+ transport at the electrode‐electrolyte interface. The bilayer SEI film has been formed via the synergistic effect of LiNO3 and vinylene carbonate, which not only improves Li+ transport in the SEI film, but also greatly facile the desolvation of Li+ at the electrode‐electrolyte interface. This expands the design strategy and promising applications of low‐concentration electrolytes.

The oxidant (e.g., hypochlorous acid, HClO) has been widely used to remediate contaminated sites. However, the effects of HClO on soil health in agricultural fields have been rarely explored. Based on the laboratory and field experiments, we found that low concentrations of HClO changed soil bioavailable elements, enzyme activities, and the structure of microbial communities. Specifically, the application of 5‰ HClO increased DOC content by 13.9-19.9% compared with CK. The bioavailable Fe and Mn contents also increased by 15.0% and 48.7%-61.8%, respectively. Correspondingly, in field experiments, 5‰ HClO enhanced the DOC contents by 12.0%. Besides, the application of HClO also elevated enzyme activities and improved the structure of the microbial community of soil. These findings might provide new strategies for improving the fertility and quality of agricultural soil.

Elevated concentration of total phosphorus (TP) or reactive phosphate (PO43−) in aquaculture wastewater (AW) can cause eutrophication in the wastewater discharge ponds. This study delves into the effectiveness of calcined eggshells (CESs) in recovering low concentrations of TP and PO43− from AW. Eggshell waste collected from domestic sources was pyrolyzed at 800 °C for 30 min. Characterization indicated that the functional groups of CES portray a significant role in the adsorption process. The nonlinear form of the Freundlich model fitted well for TP and PO43− adsorption processes from AW. CES could recover up to 96.6 and 97.3% of low concentration TP and PO43−, respectively, from AW. The adsorption indicated chemisorption activity by CES. The thermodynamic studies suggested that the adsorption of TP and PO43− were feasible, spontaneous, and exothermic in nature. This recovery process does not create secondary waste, and the recovered spent adsorbents can be utilized as garden fertilizer or as pest repellant in the aquaculture farm.

The utilization of microwave drying technology has expanded across various sectors due to its rapid processing speed, reduced operation time, lower sample temperatures, and consistent heating. In this research, microwave pretreatment was implemented prior to carbonation curing with low concentrations, and an array of tests including moisture content, compressive strength, carbonation depth, CO2 absorptivity, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were utilized to investigate the effect of microwave pretreatment on the properties and microstructure of cementitious materials under early carbonation curing with low CO2 concentrations. The findings reveal that microwave pretreatment significantly decreases the moisture content within the test specimens, expediting the ingress of CO2 and improving the compressive strength of the specimens. At the same time, the effectiveness of microwave pretreatment in reducing moisture content diminishes as the pretreatment time increases. The absorption of CO2 is relatively rapid in the early stage of carbonation curing, with over 50% of the CO2 absorption occurring within the 0–6 h period of carbonation curing. The hydration products and microstructure of the uncarbonated part inside the specimens are generally consistent with the normal curing state. The formation of CaCO3 contributed to the densification of the specimen by infilling its internal voids, thereby enhancing its compressive strength. Although carbonation curing enlarges the average pore size of the samples, it also serves a filling function, making the samples more compact and reducing the porosity.