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The 2008 Wenchuan earthquake that occurred in the Longmenshan thrust zone is the most serious natural disaster recorded in China’s densely populated areas over the past few decades. Its northeast-trending principal fault—the Yingxiu–Beichuan fault (YXBCF), has a complex, segmentary-cascaded geometry and was dominated by the thrust slip in the southwest section, while the right-lateral slip in the northeast section. Some previous works believe that there may have occurred a supershear rupture in the strike-slip-dominated northeast section. Here we revisited this earthquake by exploring the dynamic rupture mechanism of the principal fault and showed a hypothetical scenario with supershear rupture occurring in its northeast section. We utilized a 3D curve grid finite-difference method to simulate the spontaneous rupture process of the YXBCF and corresponding near-field strong ground motion. An appropriate focal process is obtained using the trial-and-error method within reasonable parameters, and its related responses are validated by geological investigations and geophysical inversions. Besides, a large hypothetical oblique propagating supershear rupture is shown between Beichuan and Nanba in the northeast section of the YXBCF. Its transition mechanism is related to the Gaochuan–Beichuan conjugated fault from the fault geometry perspective, and belongs to the joint action of fault barrier and free surface. Such a supershear scenario is not rejected by observations and could increase the credibility of the occurrence of supershear rupture in the northeast section of the YXBCF during the Wenchuan earthquake.

Reducing the flexspline (FS) deformation is important for decreasing the alternating stress, flare angle in the axial direction, spatial deformation of teeth, and tube length. However, it may increase the probability of insufficient engagement depth and nonexistent conjugate tooth profiles. In this study, a mathematical model of the harmonic drive (HD) with a new tooth profile is proposed to reduce the FS deformation while satisfying the engagement depth and existence of a conjugated tooth profile. First, the generation mechanism of the new tooth profile is discussed in detail and the connection method of the circular arc tooth profile and transition tooth profile in the FS were presented. Then, two key parameters of the model, the translation distance and offset distance were studied to design the ideal tooth profile. Finally, a tooth root chamfer method was proposed to achieve smooth operation of the HD. Additionally, owing to the lack of a wear assessment of the new tooth profile, a sliding coefficient calculation model was presented. To verify the feasibility of the models, a prototype with a radial deformation coefficient of 0.8 was designed, processed, and tested. The experimental results were consistent with the theoretical analyzes.

Uncontrollable growth of lithium (Li) dendrites and low Coulombic efficiency induce security hazards and a short cycling lifespan of Li metal batteries. In this study, well-aligned ZnO nanorods on a periodic three-dimensional (3D) copper mesh (CM) are modified as lithiophilic anchor points to regulate the electrodeposition behavior of Li metal anodes. The in situ generated LiZn/Li

In strong ground-motion observations, accelerograms are an important material in both seismic research and earthquake engineering. However, the ubiquitous baseline drift in near-field acceleration records has a large impact on the integrated velocity and double-integrated displacement with linear and parabolic drift, respectively. Conventionally, high-pass filtering and two-stage baseline fitting methods are commonly applied in baseline corrections to obtain reliable strong-motion records. However, these filtering methods exclude low-frequency components from acceleration records and cause unexpected waveform loss. The baseline fitting method, which is based on the experiential selection of intersection moments, is easily affected by external factors and requires a large amount of time for operations. Currently, as the number of accelerometers grows, conventional methods are insufficient in both efficiency and precision to process vast acceleration records. Here, we propose TraceNet, a deep-learning-based method, to correct baseline drifts in velocity records integrated from accelerograms. The training data set is developed with the fusion of artificial baselines and nondrift velocities from corrected accelerations and displacements from events. TraceNet extracts the baseline from the input velocity trace. After TraceNet prediction, the drift can be corrected by subtracting the extracted baseline. In addition, the potential coseismic ground displacement can be recovered from the integration in the corrected velocity. In this study, we used acceleration records and continuous Global Positioning System observations from the 2008 Wenchuan earthquake to demonstrate the ground offset recovery. As a deep learning application, TraceNet can extract and correct the baseline drifts automatically without subjective factors. The coseismic displacements estimated from accelerograms can provide additional insight into the ground deformation.

Wave-propelled mechanisms are applied to propel unmanned marine vehicles such as Wave Glider and wave-powered boats, which can convert wave energy directly into propulsion. In this paper, a fluid-rigid body coupled dynamic model is utilized to investigate the propulsion performance of the wave-propelled mechanism. Firstly, the coupled dynamic model of the wave-propelled mechanism is developed based on relative motion principle by combining rigid body dynamics model and CFD method. Then, the motion responses of wave-propelled mechanism are calculated. The relationship between the propulsion force, heave and pitch motion of hydrofoil are analyzed by using phase diagrams and the actual operation conditions of propulsion mechanism are obtained. Besides, the effects of restoring spring stiffness and wave heights on the propulsion performance are also investigated, and the vortex evolution is illustrated at different moments of movement and different restoring stiffness. These works can be helpful for the design and optimization of different kinds of wave-propelled vehicles.

Mn doping is deemed as a promising strategy to improve the electrochemical performance of the α-Ni(OH)2 battery-type supercapacitor electrode. However, the internal structure evolution, the pathways and the dynamics of the proton/intercalated anion migration, as well as the functioning mechanism of Mn dopant to stabilize the layered structure during cycles remain unclear. Here, we unveil that irreversible oxidization of Mn3+ at the initial CV cycles, which will remain as Mn4+ in the NiO2 slabs after the first oxidization to effectively suppress the phase transformation from α-Ni(OH)2/γ-NiOOH to β-Ni(OH)2/β-NiOOH and further maintain the structural integrity of electrode. With a synergistic combination of theoretical calculations and various structural probes including XRD and 2H MAS solid state NMR, we decode the structure evolution and dynamics in the initial CV (cyclic voltammetry) cycles, including the absorption/desorption of hydrogen containing species, migration of intercalated anions/water molecules and the change of interlayer space. This present work elucidates a close relationship between doping chemistry and structural reliability, paving a novel way of reengineering supercapacitor electrode materials.

Atomic-level structure engineering is an effective strategy to reduce mechanical degradation and boost ion transport kinetics for battery anodes. To address the electrode failure induced by large ionic radius of K+ ions, herein we synthesized Mn-doped ZnSe with modulated electronic structure for potassium ion batteries (PIBs). State-of-the-art analytical techniques and theoretical calculations were conducted to probe crystalline structure changes, ion/electron migration pathways, and micromechanical stresses evolution mechanisms. We demonstrate that the heterogeneous adjustment of the electronic structure can relieve the potassiumization-induced internal strain and improve the structural stability of battery anodes. Our work highlights the importance of the correlation between doping chemistry and mechanical stability, inspiring a pathway of structural engineering strategy toward a highly stable PIBs.

Doping have been considered as a prominent strategy to stabilize crystal structure of battery materials during the insertion and removal of alkali ions. The instructive knowledge and experience acquired from doping strategies predominate in cathode materials, but doping principle in anodes remains unclear. Here, we demonstrate that trace element doping enables stable conversion-reaction and ensures structural integrity for potassium ion battery (PIB) anodes. With a synergistic combination of X-ray tomography, structural probes, and charge reconfiguration, we encode the physical origins and structural evolution of electro-chemo-mechanical degradation in PIB anodes. By the multiple ion transport pathways created by the orderly hierarchical pores from “surface to bulk” and the homogeneous charge distribution governed in doped nanodomains, the anisotropic expansion can be significantly relieved with trace isoelectronic element doping into the host lattice, maintaining particle mechanical integrity. Our work presents a close relationship between doping chemistry and mechanical reliability, projecting a new pathway to reengineering electrode materials for next-generation energy storage.

Correction for ‘Membrane technologies in toilet urine treatment for toilet urine resource utilization: a review’ by Chengzhi Yu et al., RSC Adv., 2021, 11, 35525–35535, https://doi.org/10.1039/D1RA05816A.

Summary Solid-solid interfaces play a crucial role in fundamental aspects of electron transfer and ion transport, which determine the underlying physical phenomena and electrochemical behaviors in solid-state batteries. Nevertheless, the exact mechanisms at the solid-state battery interface have not been fully elucidated, which necessitates the localized probes to comprehensively understand their physical contact, interphase formation, interfacial instability, and mechanical properties. In this review, a variety of emerging imaging techniques to understand the local structure and chemistry at solid-state battery interfaces are overviewed, with special focus on how each imaging technique can address the key challenges at cathode-electrolyte interfaces, anode-electrolyte interfaces, and interparticle interfaces from the atomic scale to the macroscopic scale. The capabilities and limitations of these imaging methods are summarized and discussed. We also provide a vision of the state-of-the-art imaging characterization techniques and highlight new operando capabilities from cryogenic or synchrotron imaging methods to track the dynamic solid-state interface behaviors.

At the forefront of developments in synchrotron x-ray microscopy, nanoscale-resolution high-dimensional spectrotomography under controlled sample environments has been demonstrated. Such cutting-edge experimental capability has been broadly applied to scientific studies in the field of energy materials science, where the dynamically evolving structural and chemical defects play a vital role in the functionality. In this article, we review novel developments of this technique from both experimental and data/information mining perspectives. Using studies on lithium-ion battery electrode materials as examples, we highlight the rich information in the high-dimensional and high-resolution x-ray tomographic data, which can be used to interpret the complicated thermal-electro-chemo-mechanical interplay that occurs under the operating conditions and collectively determines battery performance. We also discuss the frontier challenges in this field and our perspectives of the future directions in the context of projected major developments in the landscape of large-scale x-ray facilities across the globe.

For micron-sized nickel-based hydroxides sheets, the reaction and migration of anions/water molecules in the inner region tends to lag behind those along the edge, which can cause structure mismatch and capacity degradation during cycles. Nanosizing and structure design is a feasible solution to shorten the ion/electron path and improve the reaction homogeneity. Herein, this study reports a novel three-stage strategy (self-assembly of NiMn-LDH/ppy-C - reduction to NiMn/ppy-C - in situ phase transformation into NiMn/NiMn-LDH/ppy-C) to reduce the sheet size of NiMn-LDH to nanometer. Triggered by electrochemical activation, NiMn-LDH nanosheets can hereby easily and orderly grow on the exposed active (111) crystal plane of Ni to establish NiMn-LDH/NiMn heterostructure around ppy-C. Importantly, nanosizing and hierarchical structure play a synergistic role to maintain structural integrity and to promote the electron/mass transfer kinetics. The NiMn/NiMn-LDH/ppy-C composite delivers superior cycling stability with almost no decay of capacity retention after 40,000 cycles at 5 A g

A clear understanding of algal cell adhesion and cake layer evolution in algal-related membrane processes (ARMPs) is urgently required to mitigate the membrane fouling. In this study, the effect of microparticles (10 μm-30 μm), subvisible particles (0.45 μm-10 μm), and ultrafine particles (50 kDa-0.45 μm) on the membrane fouling were explored based on the filtration performance through Hermia models, thermodynamic analysis, and simulation of extended discrete element method (EDEM). The results illustrated that microparticles played an important role in algal cell aggregation and the formation of initial clusters. Intermediate blocking fouling occurred when filtrating the subvisible particle, which facilitated internal adhesion and enhanced biofilm formation. In addition, the interfacial attractive force for the initial algal adhesion was obviously increased when the membrane surfaces were in high concentration of protein and polysaccharide. Moreover, the EDEM simulation demonstrated that subsequent particles, particularly the particles with small sizes, preferred to occupy the spaces among the previously deposited particles. This study provided new insights into the contributions of size-fractioned particles to initial fouling and their influence on the successive adhesion of other contaminants.

A harmonic reducer (HR) is widely used because of high precision, small size, light weight and a series of advantages. However, the disadvantage is that its transmission ratio is generally not less than 60. According to a market research study, more than 60% of the reducers have the transmission ratio of less than 60. This implies that the large transmission ratio restricts the HR from applications in the market demanding a small transmission ratio (20–60). In this study, a method is presented for designing the HR with the small transmission ratio as low as 20. First, by clarifying the principle of reducing the transmission ratio of the HR, a design model of two-wave HR tooth profile is deduced in detail, and a four-tooth difference HR is designed. Aiming at solving the problem that diminishing the radial deformation coefficient leads to the reduction of the engagement depth and the increase of the pressure angle of the tooth profile, a wave generator with a new profile is proposed. Then an optimization model based on the circular spline tooth profile to envelope the flexspline tooth profile is developed for achieving the twice-conjugated engagement. Based on manufacturing considerations, the theoretical tooth profile is fitted by involute based on a given numerical approximation method. Third, a finite element analysis is carried out to investigate the stress characteristics of small transmission ratio HR. Finally, a prototype with a transmission ratio of 20 is trial-produced and tested, which shows that the design methods can be applied for the small transmission ratio HR.

Kinematic error is an important indicator for evaluating the performance of harmonic drive gears. Previous methods for calculating the kinematic error only considered a single meshing tooth, the effect of other meshing teeth was compensated by the error homogenization coefficient. Because of the complex contact state of harmonic drive gears, the results of these methods are always inconsistent with experimental results. This paper proposes a mathematical model considering all meshing teeth to predict the pure kinematic error of harmonic drive gears. First, the contact points on each meshing tooth are determined, and the contact states of the flexspline and circular spline teeth are investigated. Then, the contact forces on the meshing teeth are obtained, and the pure kinematic error is calculated based on the relationship between the torque caused by the contact force on the left and the right tooth profiles. Finally, the mathematical model is validated by simulation and experimental methods. The study in this paper can not only be used to accurately predict the pure kinematic error but also is valuable in the selective assembly of higher precision harmonic drive gears.

The microalgal wastewater cyclic cultivation technology (AWC

Compared to the significant advances in its lithium and sodium analogue, the practical application of potassium ion batteries (KIBs) has been hindered by the sluggish K ion diffusion. Electrochemical storage via insertion/de-insertion reactions in lamellar electrode materials critically rests upon the host materials with wide interlayer spacing and the sizes of the guest ions. To uncover the underlying science behind the dimensionality in the KIBs regime, we investigated MoS2/K half-cell using uniform MoS2 rod, sheet, and sphere structures synthesized by a facile and controllable method for the first time. Impressively, when MoS2 is in the shape of a hierarchical rod, there is more intercalation pseudocapacitance (74.8% at the scan rate of 1.5 mV s−1) and the optimized electrode resulted in high-rate capacity (320 and 183 mAh g−1 at 0.1 and 1 A g−1, respectively). In contrast, MoS2 sheet and sphere contribute little pseudocapacitance (69.1% and 61.4%, respectively) and therefore exhibit low-rate capacity (232 and 110 mAh g−1 for MoS2 sheet, 185 and 96 mAh g−1 for MoS2 sphere at 0.1 and 1 A g−1, respectively). Density functional theory (DFT) results uncover that the K atom is much more liable to occupy the octahedral (Oh) site. What’s more, non-destructively 3D reconstruction of MoS2 rod electrode strongly demonstrated the integrity of the rod structure after K+ insertion. The work paves a new way for the design of two dimensional (2D) materials and offers profound insights into the charge storage mechanism of KIBs.

Prussian blue analogues (PBAs) have been regarded as prospective cathode materials for sodium-ion batteries due to tunable chemical composition and structure. Herein, a high-performance rhombohedral nickel hexacyanoferrate is synthesized via a controllable low-temperature reaction process. It can deliver impressive capacity retention of 87.8% after 10 000 cycles at 10C and high rate discharge capacity of 53 mAh g

In this paper, NiO nanoparticles uniformly embedded in spherical carbon matix in situ grown on reduced graphene oxide (rGO) has been successfully fabricated via a simple pyrolysis of nickel metal organic framework (MOF) precursor self-assembled on graphene oxide. This interaction between the carbon and the NiO can significantly maximize the surface of NiO for pseudocapacitance, provide effective electronical transmission path and improve the ionic absorbability and conductivity. As a result, the NiO/C/rGO hybrid electrode demonstrates high specific capacity (496 C g−1 at current density of 1 A g−1) and good cycling stability. Moreover, a hybrid supercapacitor assembled by NiO/C/rGO and a hierarchical porous carbon derived from sodium citrate can deliver a high energy density of 35.9 Wh kg−1 at a power density of 749.1 W kg−1, and extraordinary cycling stability (120% retention after 3000 cycles). It has been demonstrated that the carbon matrix derived from the linker molecules in Ni-MOF, which maintains close contact with both the size-controlled NiO nanocrystals and the electronic conductive rGO, is vital to synergize the electric double layer capacitance from the carbon materials and the battety-type behavior from NiO for high-performance energy storage.

Electrochemical storage via conversion reactions in crystalline electrode materials critically rests upon the sizes of the guest ions. Here we report an unusual behavior that renders CuO inactive i...

Membrane technologies have broad potential in methods for separating, collecting, storing, and utilizing urine collected from toilets. Recovering urine from toilets for resource utilization instead of treating it in a sewage treatment plant not only reduces extra energy consumption for the degradation of N and P but also saves energy in chemical fertilizer production, which will contribute to carbon emission reduction of 12.19–17.82 kg kgN−1 in terms of N alone. Due to its high efficiency in terms of volume reduction, water recycling, nutrient recovery, and pollutant removal, membrane technology is a promising technology for resource utilization from urine collected from toilets. In this review, we divide membrane technologies for resource utilization from urine collected from toilets into four categories based on the driving force: external pressure-driven membrane technology, vapor pressure-driven membrane technology, chemical potential-driven membrane technology, and electric field-driven membrane technology. These technologies influence factors such as: recovery targets and mechanisms, reaction condition optimization, and process efficiency, and these are all discussed in this review. Finally, a toilet with source-separation is suggested. In the future, membrane technology research should focus on the practical application of source-separation toilets, membrane fouling prevention, and energy consumption evaluation. This review may provide theoretical support for the resource utilization of urine collected from toilets that is based on membrane technology.

The transfer of an ultrathin membrane onto arbitrary substrates is important in different practical fields. Conventional wet-transfer methods inevitably induce wrinkle defects as a result of the large contact angle of the trapped droplet between the membrane and the substrate. Here, we demonstrate a gas flow-assisted method (GFAM) to transfer centimeter (cm)-scale ultrathin membranes onto arbitrary substrates (including a curved substrate) without wrinkles. GFAM makes use of contact angle hysteresis to bulge the trapped droplet between the substrate and the ultrathin membrane and simultaneously stretch the ultrathin membrane during rapid dewetting driven by gas flow. Moreover, GFAM can be easily fulfilled by using compressed air for seconds. Compared with conventional hydrophilic treatments or organic liquid wetting, this method has no durability concern and does not change the surface nature of substrates. Taking a widely used ultrathin anodic aluminum oxide (AAO) membrane as an example, we successfully demonstrate the application of a large-area wrinkle-free ultrathin AAO membrane to defect-free ordered nanostructure array fabrication and investigate the micro-scale details of macro-scale wrinkles generated by the conventional ways. In addition, its corresponding superiority over the defective counterpart is further studied in optical sensing. This method is highly valuable for promoting the simplicity of large-area ultrathin membrane transfer in practice.

Interfacial issues commonly exist in solid-state batteries, and the microstructural complexity combines with the chemical heterogeneity to govern the local interfacial chemistry. The conventional wisdom suggests that “point-to-point” ion diffusion at the interface determines the ion transport kinetics. Here, we show that solid-solid ion transport kinetics are not only impacted by the physical interfacial contact but are also closely associated with the interior local environments within polycrystalline particles. In spite of the initial discrete interfacial contact, solid-state batteries may still display homogeneous lithium-ion transportation owing to the chemical potential force to achieve an ionic-electronic equilibrium. Nevertheless, once the interior local environment within secondary particle is disrupted upon cycling, it triggers charge distribution from homogeneity to heterogeneity and leads to fast capacity fading. Our work highlights the importance of interior local environment within polycrystalline particles for electrochemical reactions in solid-state batteries and provides crucial insights into underlying mechanism in interfacial transport., Solid state battery is regarded as one of the most promising next generation energy storage systems due to high safety and high energy density. Here, authors demonstrate the importance of interfacial local environment in polycrystalline cathodes for electrochemical reactions in solid-state batteries.

Sulfur atoms can reconstruct the configuration of PAN, which makes the electron transfer more convenient and reduces the energy barriers during Li ion diffusion. The sulfurized polyacrylonitrile plays a crucial role in anchoring the P4 molecule and electron transport simultaneously. Uniform RP nanoparticles (∼200 nm) are obtained using a simple liquid phase method. SPAN-RP shows an initial reversible capacity of 1214 mA h g-1 at 0.2C and retains a capacity of 860 mA h g-1 with a high coulombic efficiency of 99.6% after 200 cycles.

The defect and N-doping engineering are critical to developing the highly efficient metal-free electrocatalysts for oxygen reduction reaction (ORR), mainly because they can efficiently regulate the geometric/electronic structures and sur-/interface properties of the carbon matrix. Herein, we provide a facile and scalable strategy for the large-scale synthesis of N-doped porous carbon nanosheets (NPCNs) with hierarchical pore structure, only involving solvothermal and pyrolysis processes. Additionally, the turnover frequency of ORR (TOFORR) was calculated by taking into account the electron-transfer number (n). Benefiting from the trimodal pore structures, high specific surface area, a higher pore volume, high-ratio mesopores, massive vacancies/long-range structural defects, and high-content pyridinic-N (~2.1%), the NPCNs-1000 shows an excellent ORR activity (1600 rpm, js = ~5.99 mA cm−2), a selectivity to four-electron ORR (~100%) and a superior stability in both the three-electrode tests (CP test for 7500 s at 0.8 V, Δjs = ~0.58 mA cm−2) and Zn–Air battery (a negligible loss of 0.08 V within 265 h). Besides, the experimental results indicate that the enhancement of ORR activity mainly originates from the defects and pyridinic-N. More significantly, this work is expected to realize green and efficient energy storage and conversion along with the carbon peaking and carbon neutrality goals.

A uniform shearing vibration membrane system can mitigate membrane fouling during algae filtration. In this paper, the effects of transmembrane pressure (TMP) on the membrane filtration performance at 8 kPa, 9 kPa and 10 kPa were investigated. The results of membrane fouling mechanisms predicted by Hermia's model surmised that membrane fouling is principally caused by the cake layer model, and the application of the Unified Membrane Fouling Index for quantitative evaluation of antifouling properties substantiating membranes in sub-critical condition exhibited superior antifouling properties. The reversible membrane fouling was largely dependent on polysaccharides due to size exclusion. Proteins tended to block the membrane pores and to cause irreversible fouling. It was also observed that high-molecular weight (>100 kDa) extracellular organic matters contributed a significant portion of membrane fouling. For greater insight, the CRiteria Importance Through Intercriteria Correlation (CRITIC) method was administered; it could be concluded that the removal of proteins was more responsible for the total fouling resistance than was the removal of polysaccharides, especially for membranes at the TMP of 9 kPa.

Magnetic composites SrFe12O19/ZnFe2O4 were successfully synthesized by one-pot coprecipitation method. The as-prepared samples with different molar ratio of SrFe12O19 to ZnFe2O4 were characterized and analysed. XRD and SEM results show that the composites are highly crystalline with few impurities. Raman spectrum confirms the interactions between two phases in the composites. UV–vis spectra and photoluminescence spectra show the optical property of the samples. The magnetic properties analysis reveals that the coercivity of composites decrease evidently with the increase of the ZnFe2O4 phase. Furthermore, photocatalytic performance of the samples were investigated by the degradation of methylene blue (MB) under visible light irradiation. The maximum degradation ratio of MB with Sample-A was 90%. The recycling tests confirm that the photocatalytic activity was above 50% after three cycles. These all prove that the composite SrFe12O19 and ZnFe2O4 not only improve the magnetic and photocatalytic properties, but also effectively avoid secondary pollution of treated water.

When a membrane is used to harvest algae, membrane fouling caused by algae and extracellular organic matter (EOM) is a serious challenge. A uniform shearing vibration membrane (USVM) system was devised and applied to reducing membrane fouling in algae filtration. The shear rate produced by USVM is constant because of its uniform circular motion; thus, USVM could stably and significantly mitigate fouling. During the filtration experiments where the frequency was increased from 1 to 5 Hz, the transmembrane pressure (TMP) visibly reduced. Even at a relatively low frequency of 5 Hz, USVM still could stably filter algae and had only slight membrane fouling. Increasing the vibration frequency not only could significantly reduce reversible membrane fouling but could also reduce irreversible membrane fouling. Protein could cause more serious reversible membrane fouling, while humic substances could lead to more serious irreversible membrane fouling. In this study, USVM effectively reduced the deposition of algae cells, protein, polysaccharide and humic substances on the membrane as frequency increased.

In this paper, a novel flower-like BiOI/MnO2 composite was synthesized by two simple steps. The crystal structure, morphology, surface element analysis, and optical properties of as-prepared samples were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectrometry (DRS). Photocatalytic activities of the prepared photocatalysts were evaluated by photocatalytic degradation of RhB under simulated light irradiation. When 50 mg of a BiOI/MnO2 composite with a mass ratio of 5/1 was used to degrade RhB aqueous solution (100 mL, 20 mg L−1), the degradation efficiency could reach 99.18% within 60 min under simulated solar light irradiation. In addition, the photocatalyst exhibited good stability. After four cycles, the degradation efficiency of the BiOI/MnO2 (5/1) composite could reach 92.8% within 80 min. The probable photocatalytic mechanism of photocatalysts was investigated by active species trapping experiments and photoluminescence (PL) measurements. The results showed that the superior photocatalytic activity of the BiOI/MnO2 composite is derived from the generation and transfer of photogenerated carriers between MnO2 and BiOI.

A novel Co@MXenes catalyst with unique structure was prepared through randomly anchoring cobalt on 2D sandwich-like MXenes to activate peracetic acid (PAA) for water decontamination. Compared to the conventional Co3O4 nanomaterial, the Co@MXenes catalyst exhibits superior performance for PAA activation under neutral condition. In-depth investigation revealed that the Ti3C2Tx MXene substrate triggered the ≡ Co(III)/≡ Co(II) cycle, which greatly enhanced the activation of PAA. The XPS and ICP techniques further demonstrated that Co@MXenes was highly stable with extremely low cobalt ion leaching and hence a superior reusability was obtained. Moreover, acetylperoxyl radical (CH3CO3 ) was identified as the primary radical species responsible for organic micropollutants degradation, exhibiting high selectivity towards contaminants containing electron-rich groups. The novel technology exhibited a high tolerance of Cl− and good performance in real wastewater treatment. This work provides a promising effective catalyst for PAA activation and will facilitate PAA application in wastewater decontamination.