科研成果

Concurrently elevating the degradation efficiency of pollutants and realizing the reduction of iron sludge in Fe-based catalytic ozonation is important but still challenging. Herein, we developed an electrocatalytic ozonation (ECO) system with iron plate cathode and graphite felt anode (ECO-Fe-cathode), which was free from added chemical reagents. Unlike the iron plate as a sacrificial anode in the ECO (ECO-Fe-anode) system, this delicately designed system shows a much higher degradation rate of ibuprofen (kobs = 1.490 min−1) than that of the ECO-Fe-anode system (kobs = 0.345 min−1). Simultaneously, the effluent was totally limpid without the corrosion of iron plates and the formation of iron sludge in the ECO-Fe-cathode system. Unexpectedly, the generation of singlet oxygen (1O2) which is indirectly generated by the single-electron transfer derived from superoxide ion (O2•-) is the primary reactive oxygen species (ROS) in the ECO-Fe-cathode system, which is different from the ECO-Fe-anode system with hydroxyl radicals (•OH). Moreover, linear sweep voltammetry (LSV) was applied to reveal the oxygen evolution reaction (OER) performance of the iron plate and graphite felt, and the results showed that graphite felt as anode has better electrocatalytic performance. The electrochemical analysis and density functional theory (DFT) calculation revealed that ozone adsorbed on the iron plate surface is more conducive to facilitating and triggering subsequent reactions. Finally, the different degradation pathways of ibuprofen in both systems were proposed. This work represents a fundamental breakthrough toward the design of an efficient and harmless ECO system for wastewater treatment.

Rationally regulating reaction mechanisms in Fenton-like reactions by tuning the properties of catalysts is of great significance, but still challenging. Herein, we synthesized various active center size-dependent catalysts to realize the switching of reaction mechanisms and pollutant degradation routes in peroxymonosulfate (PMS) activation systems. The results illustrated that the reaction mechanism transformed from radical oxidation (51.64%) to nonradical oxidation (89.92%) with the decrease of active center size from nanoparticle (CoNP-NC) to single atom (CoSA-NC). The evolution of reactive species switched the degradation intermediates and pathway of sulfisoxazole (SIZ). The generation of singlet oxygen (1O2) in CoSA-NC/PMS tends to selectively attack electron-rich site of SIZ, while reaction between radicals and SIZ prefers non-selective oxidation in CoNP-NC/PMS system. Besides, the toxicity tests indicated that the conversion from non-selective to selective oxidation resulted in lower toxicity of effluent after reaction, which can further reduce environmental risks of effluent.

Abstract Complementary metal-oxide-semiconductor (CMOS) field-effect transistors (FETs) are the key component of a chip. Bulk indium arsenide (InAs) owns nearly 30 times higher electron mobility µe than silicon but suffers from a much lower hole mobility µh (µe/µh = 80), thus unsuited to CMOS application with a single material. Through the accurate ab initio quantum-transport simulations, the performance gap between the NMOS and PMOS is significantly narrowed is predicted and even vanished in the sub-2-nm-diameter gate-all-around (GAA) InAs nanowires (NW) FETs because the inversion of the light and heavy hole bands occurs when the diameter is shorter than 3 nm. It is further proposed several feasible strategies for further improving the performance symmetry in the GAA InAs NWFETs. Short-channel effects are effectively depressed in the symmetric n- and p-type GAA InAs NWFETs till the gate length is scaled down to 2 nm according to the standards of the International Technology Roadmap for Semiconductors. Therefore, the ultrasmall GAA InAs NWFETs possess tremendous prospects in CMOS integrated circuits.

A Fe-doped CeO2 was fabricated for catalytic ozonation of Amoxicillin (AMX), and the catalytic mechanisms were explored in this study. Under optimal conditions (the initial solution pH of 7.0, FC-0.3 dosage of 0.5 g/L, O3 dosage of 4 mg/min), the AMX and TOC removal by the optimal material (FC-0.3, at Fe/Ce atomic ratio of 0.3) reached 98.1% at 24 min and 55.2% at 36 min, respectively. Improved the AMX mineralization efficiency by 3.7 times. The experiments and theoretical calculation reveal the mechanisms of promoted catalytic ozonation by FC-0.3: 1) Highly abundant surface-active sites (i.e., -OH) enabled the adsorption of H2O and O3, which was favorable to the generation of reactive oxygen species (ROS) and improved the reaction probability for ROS and contaminants. 2) The synergistic effect between Ce4+/Ce3+ and Fe3+/Fe2+ redox couples accelerated the electron transfer and formation of ROS. More than 42% of •OH was generated in the presence of FC-0.3, and the •OH, •O2− and 1O2 were the main ROS that contributed to AMX degradation. The surface OH groups played a key role in the catalytic ozonation. The oxygen vacancies (OVs) played an important role in electron transfer, Ce and Fe were the active sites of electrons transfer following the sequence of (Ce3+ + Fe2+) → (Ce4+ + Fe3+) → (Ce3+ + Fe2+) redox reaction. The degradation pathway investigation and toxicity evaluation revealed that some more toxic intermediates were generated during the ozonation process, and sufficient mineralization is required to meet safe discharge. This study provides reference for the synthesis of new catalysts and insight into the reaction mechanisms in the heterogeneous catalytic ozonation process.

Organophosphorus pesticides are extensively utilized worldwide, but their incomplete dephosphorization poses significant environmental risks. This study investigates the dephosphorization of dimethoate (DMT), a representative organophosphorus pesticide, using a vacuum ultraviolet system. Surprisingly, in addition to hydroxyl radicals (•OH), non-radical processes such as photoexcitation and singlet oxygen atoms (O(1D)) exert more significant effects on DMT dephosphorization. The degradation kinetics of DMT demonstrate a perfect linear correlation with the radical yield in both UV-based and VUV-based advanced oxidation processes (AOPs), with greater efficacy of radical attack observed in the VUV system. This heightened efficiency is attributed to the excitation of DMT to a high-energy excited state induced by UV185 radiation. Additionally, •OH alone is inadequate for achieving complete dephosphorization of DMT. The Fukui index and singly occupied orbital (SOMO) analysis reveal that the O(1D) generated by UV185-induced photolysis of O2 exhibits exceptional selectivity towards P=S bonds, thereby playing an indispensable role in the dephosphorization process of DMT. This study highlights the significant contribution of non-radical pathways in DMT dephosphorization by VUV, which holds great implications for the advancement of photochemical-based AOPs.

Traditional methods cannot efficiently recover Cu from Cu(II)–EDTA wastewater and encounter the formation of secondary contaminants. In this study, an ozone/percarbonate (O3/SPC) process was proposed to efficiently decomplex Cu(II)–EDTA and simultaneously recover Cu. The results demonstrate that the O3/SPC process achieves 100% recovery of Cu with the corresponding kobs value of 0.103 min–1 compared with the typical •OH-based O3/H2O2 process (81.2%, 0.042 min–1). The carbonate radical anion (CO3•–) is generated from the O3/SPC process and carries out the targeted attack of amino groups of Cu(II)–EDTA for decarboxylation and deamination processes, resulting in successive cleavage of Cu–O and Cu–N bonds. In comparison, the •OH-based O3/H2O2 process is predominantly responsible for the breakage of Cu–O bonds via decarboxylation and formic acid removal. Moreover, the released Cu(II) can be transformed into stable copper precipitates by employing an endogenous precipitant (CO32–), accompanied by toxic-free byproducts in the O3/SPC process. More importantly, the O3/SPC process exhibits excellent metal recovery in the treatment of real copper electroplating wastewater and other metal–EDTA complexes. This study provides a promising technology and opens a new avenue for the efficient decomplexation of metal–organic complexes with simultaneous recovery of valuable metal resources.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

Coatings often cover two-thirds of the surfaces in indoor environments and represent important sources of indoor volatile organic compounds (VOCs). Temperature is known to affect VOC emission rates from coatings, yet inter-species difference in the temperature dependence still needs to be understood. Based on time-resolved VOC measurements in an indoor air campaign conducted in residences in Beijing, China, we identified dibasic ester (DBE), a solvent mixture often used in coatings, and found that the concentration ratios of DBE components exhibited strong temperature dependence in an apartment when the indoor temperature declined stepwise over a multiweek period. To interpret the observational results, we developed a simplified mechanistic model relating the temperature dependence of VOC emission rates from coated surfaces to the temperature dependence of the diffusion coefficient of the emitted VOCs in the coating layer and further to a predicable molecular property of the emitted VOCs, molar volumes at 0 K, based on the free-volume theory. This correlation was quantitatively verified using the DBE data as well as using the data of alkanes, another set of VOCs that might be emitted from coatings, observed in two apartments in the same campaign. Given that indoor temperature varies considerably over seasons and across regions, the correlation proposed herein may help better predict indoor VOC emissions from coatings.

Seismic measurements made on Mars indicate that the liquid iron‐nickel core is rich in light elements; however, the effects of these light components on the elasticity of Mars' core remain poorly constrained. Here, we calculate elastic properties of various liquid Fe‐X (X = Ni, S, C, O and H) mixtures using ab initio molecular dynamics simulations. We find that, at martian core conditions, the addition of S and O most effectively decreases the density of liquid iron, followed by C and H, while Ni has a minimal effect. As for compressional sound velocity (Vp), C increases Vp of liquid Fe throughout Mars' core, while both S and O reduce Vp, the intensity of which diminishes with increasing pressure. Assuming a martian core made of a binary mixture, the seismically‐inferred density would require the presence of at least 30 wt% S.

The time domain boundary element method (TDBEM) is suitable for dealing with dynamic problems in the semi-infinite domain (such as the propagation of seismic waves). The fundamental solution in the TDBEM is an impulse function with time terms, and the formed coefficient matrix is sparse. In this paper, a TDBEM using the compressed storage algorithm based on Compressed Sparse Row (CSR) format is proposed to solve the semi-infinite domain dynamics problems. The coefficient matrix is stored in the CSR format, and the generation method of the coefficient matrix elements and the matrix operation scheme based on CSR format in the TDBEM are given. The GMRES algorithm is also modified to make it suitable for TDBEM of CSR format to improve the efficiency of iterative solution. The provided semi-infinite domain dynamics examples show that the TDBEM of CSR format proposed in this paper can greatly reduce the storage space and improve the efficiency and scale of the solution.

arXiv:2212.09435

Traditional advanced oxidation processes (AOPs) generally suffer from the inevitable deactivation of catalysts and the ineffective consumption of transient reactive species (TRSs) that compromise the efficiency in destructing aqueous contaminants. Herein, it was interestingly found that trace Mn(II) could robustly catalyze the oxidation of organic contaminants by periodate (PI), with the performance was much better than the representative TRSs-dominated AOPs (i.e., the Fe(II)-activated hydrogen peroxide, peroxymonosulfate (PMS), peroxydisulfate and PI processes). Multiple lines of evidence excluded the oxidative contributions of TRSs, instead the stoichiometric formation of colloidal MnO2 via the condensation of di-μ-oxo-bridged Mn(IV) cluster was confirmed by UV-vis, X-ray absorption near edge structure spectroscopy and density functional theory calculation. Dependent on the structure of substrate, MnO2 colloids solely or simultaneously served as oxidant and catalyst for the enhanced treatment performance. Benefiting from the non-TRSs-involved oxidation strategy and the catalytic effects of Mn species, the trace-Mn(II)/PI process even outperformed the Co(II)-activated PMS counterpart (i.e., one of the most efficient AOPs known at present) on oxidant utilization efficiency. This study not only elucidated the roles of Mn(II) and colloidal MnO2 in PI-mediated contaminant degradation, but also signified the superiority of trace catalyst-assisted process without TRSs involvement in avoiding undesired side reactions and maximizing oxidation efficiency.

Peracetic acid combined ultraviolet (UV/PAA) process has garnered growing attention as a promising advanced oxidation process (AOP) for wastewater treatment, but the corresponding transformation of ubiquitous dissolved organic matter (DOM) under this AOP remains unknown. This study systematically investigated the changes in characteristics and composition of DOM under UV/PAA, as well as the underlying mechanisms by multiple spectroscopic analyses and Fourier transform ion cyclotron resonance mass spectrometry. UV/PAA treatment dramatically decreased aromaticity, apparent molecular weight, and fluorescent abundance of DOM with the production of more oxidized and saturated compounds. The reactive species (i.e., ·OH and CH3C(O)O·/CH3C(O)OO·) in UV/PAA contributed primarily to DOM changes but showed different reaction selectivity and mechanisms. ·OH reacts with DOM components and mainly yields oxygenation products via a radical addition pathway. Comparatively, the electron transfer route is more likely to occur in CH3C(O)O·/CH3C(O)OO·-induced DOM transformation. Aside from oxygenation products, electron transfer could exclusively generate decarboxylation products and distinguishes CH3C(O)O·/CH3C(O)OO·-based AOPs from ·OH-based AOPs. These findings significantly improve knowledge of DOM alterations under UV/PAA AOP at both the bulk and molecular levels.