Unraveling Valence Electron Number Dependent Excitonic Effects over M1-N3C1 Sites in Single-Atom Catalysts.

Excitonic effects significantly influence the selective generation of reactive oxygen species and photothermal conversion efficiency in photocatalytic reactions; however, the intrinsic factors governing excitonic effects remain elusive. Herein, a series of single-atom catalysts with well-defined M1-N3C1 (M = Mn, Fe, Co, and Ni) active sites are designed and synthesized to investigate the structure-activity relationship between photocatalytic materials and excitonic effects. Comprehensive characterization and theoretical calculations unveil that excitonic effects are positively correlated with the number of valence electrons in single metal atoms. The single Mn atom with 5.93 valence electrons exhibits the weakest excitonic effects, which dominate superoxide radical (O2•-) generation through charge transfer and enhance photothermal conversion efficiency. Conversely, the single Ni atom with 9.27 valence electrons exhibits the strongest excitonic effects, dominating singlet oxygen (1O2) generation via energy transfer while suppressing photothermal conversion efficiency. Based on the valence electron number dependent excitonic effects, a reaction environment with hyperthermia and abundant cytotoxic O2•- is designed, achieving efficient and stable water disinfection. This work reveals single metal atom dependent excitonic effects and presents an atomic-level methodology for catalytic application targeted reaction environment tailoring.

Catalytic ozonation mechanism over M1-N3C1 active sites.

The structure-activity relationship in catalytic ozonation remains unclear, hindering the understanding of activity origins. Here, we report activity trends in catalytic ozonation using a series of single-atom catalysts with well-defined M1-N3C1 (M: manganese, ferrum, cobalt, and nickel) active sites. The M1-N3C1 units induce locally polarized M - C bonds to capture ozone molecules onto M atoms and serve as electron shuttles for catalytic ozonation, exhibiting excellent catalytic activities (at least 527 times higher than commercial manganese dioxide). The combined in situ characterization and theoretical calculations reveal single metal atom-dependent catalytic activity, with surface atomic oxygen reactivity identified as a descriptor for the structure-activity relationship in catalytic ozonation. Additionally, the dissociation barrier of surface peroxide species is proposed as a descriptor for the structure-activity relationship in ozone decomposition. These findings provide guidelines for designing high-performance catalytic ozonation catalysts and enhance the atomic-level mechanistic understanding of the integral control of ozone and methyl mercaptan.

Solar-driven strongly coupled plasmonic Au nanoarrays on mesoporous silica nanodisks enable selective fungal and bacterial inactivation in well water.

Well water is an important water source in isolated rural areas but easily suffers from microbial contamination. Herein, we anchored periodic Au nanoarrays on mesoporous silica nanodisks (Au-MSN) to fabricate a solar-driven nano-stove for well water disinfection. The solar/Au-MSN process completely inactivated 3.98, 6.55, 7.11 log10 cfu/mL, and 3.37 log10 pfu/mL of Aspergillus niger spores, Escherichia coli, chlorine-resistant Spingopyxis sp. BM1-1, and bacteriophage MS2 within 5 min, respectively. Moreover, the complete inactivation of various microorganisms (even at a viable but nonculturable state) was achieved in the flow-through reactor under natural solar light in real well water matrixes. Thorough characterizations and theoretical simulations verified that the densely anchoring strategy of Au-MSN's nanoarray worked on broadband absorption via the photon confinement effect, and trace amounts of Au can induce strong electromagnetic fields and collective localized heating. The resulting surge of 1O2 and heat synergically destroyed membranes, dysfunction cellular self-defense and metabolic system, induced intracellular oxidative stress, and ultimately inactivated microorganisms. Additionally, the 1O2-dominated oxidation and cell adhesion facilitated the selective disinfection in real well water matrixes. This study provides a cost-effective and practical solution for efficient well water disinfection, which assists isolated rural areas in getting safe drinking water.

Precisely Orientating Atomic Array in One-Dimension Tellurium Microneedles Enhances Intrinsic Piezoelectricity for an Efficient Piezo-Catalytic Sterilization.

Comprehensively understanding the interdependency between the orientated atomic array and intrinsic piezoelectricity in one-dimension (1D) tellurium (Te) crystals will greatly benefit their practical piezo-catalytic applications. Herein, we successfully synthesized the various 1D Te microneedles by precisely orientating the atomic growth orientation by tuning (100)/(110) planes ratios (Te-0.6, Te-0.3, Te-0.4) to reveal the secrets of piezoelectricity. Explicitly, the theoretical simulations and experimental results have solidly validated that the Te-0.6 microneedle grown along the [110] orientation possesses a stronger asymmetric distribution of Te atoms array causing the enhanced dipole moment and in-plane polarization, which boosts a higher transfer and separation efficiency of the electron and hole pairs and a higher piezoelectric potential under the same stress. Additionally, the orientated atomic array along the [110] has p antibonding states with a higher energy level, resulting in a higher CB potential and a broadened band gap. Meanwhile, it also has a much lower barrier toward the valid adsorption of H2O and O2 molecules over other orientations, effectively conducive to the production of reactive oxygen species (ROS) for the efficient piezo-catalytic sterilization. Therefore, this study not only broadens the fundamental perspectives in understanding the intrinsic mechanism of piezoelectricity in 1D Te crystals but also provides a candidate 1D Te microneedle for practical piezo-catalytic applications.

Photo-sterilization of groundwater by tellurium and enhancement by micro/nano bubbles.

In rural areas where low-temperature groundwater is used as a drinking water source, cost-effective sterilization techniques are needed to prevent groundwater consumers from the disease risks triggered by pathogenic microorganisms like Escherichia coli and fungal spores. In this study, micro/nano bubbles (MNBs) coupled with the tellurium (Te)-based catalysts were used to considerably enhance the solar disinfection (SODIS) efficiency while overcoming the intrinsic defects of SODIS, particularly in low-temperature. Sterilization tests showed that 6.5 log10 cfu/mL of E. coli K-12 and 4.0 log10 cfu/mL of Aspergillus niger spores were completely inactivated within 5 min while applying this novel process for disinfection of raw groundwater, even in low-temperature. The underlying mechanisms of the extraordinary sterilization efficiency were revealed through comprehensive characterization of the catalysts and the physiological changes of the microorganisms. The localized surface plasmon resonance (LSPR) effect of the Te catalysts was identified to take advantage of photothermal synergism to achieve cell death. The integration of MNBs with the facet-engineered Te catalysts improved the photothermal catalytic effect and extracellular electron transfer, which substantially strengthened disinfection efficiency. This study provides a targeted solution into microbial inactivation in groundwater and emphasizes a cost-effective groundwater sterilization process.

Nanomaterial-enabled photothermal-based solar water disinfection processes: Fundamentals, recent advances, and mechanisms.

The pathogenic microorganisms in water pose a great threat to human health. Photothermal and photothermocatalytic disinfection using nanomaterials (NPs) has offered a promising and effective strategy to address the challenges in solar water disinfection (SODIS), especially in the point-of-use operations. This review aims at providing comprehensive and state-of-the-art knowledge of photothermal-based disinfection by NPs. The fundamentals and principles of photothermal-based disinfection were first introduced. Then, recent advances in developing photothermal/photothermocatalytic catalysts were systematically summarized. The light-to-heat conversion and disinfection performance of a large variety of photothermal materials were presented. Given the complicated mechanisms of photothermal-based disinfection, the attacks from reactive oxygen species and heat, the destruction of bacterial cells, and the antibacterial effects of released metal ions were highlighted. Finally, future challenges and opportunities associated with the development of cost-effective photothermal/photothermocatalytic disinfection systems were outlined. This review will provide guidance in designing future NPs and inspire more research efforts from environmental nano-communities to move towards practical water disinfection operations.

Enhanced Catalytic Ozonation for Eliminating CH3SH via Stable and Circular Electronic Metal-Support Interactions of Si-O-Mn Bonds with Low Mn Loading.

Catalytic ozonation of methyl mercaptan (CH3SH) can effectively control this unbearable odorous sulfur-containing volatile organic compound (S-VOC). The construction of an electronic metal-support interaction (EMSI) coordination structure to maximize the number of active sites and increase the intrinsic activity of active sites is an effective means to improve catalytic performance. In this work, the abundant Si-OH groups on PSBA-15 (SBA-15 before calcination) were used to anchor Mn to form a Si-O-Mn-based EMSI coordination structure. Detailed characterizations and theoretical simulations reveal that the strong EMSI effect significantly adjusts and stabilizes the electronic structure of Mn 3d states, resulting in an electron-rich center on the Si-O-Mn bond to promote the specific adsorption/activation of ozone (O3) and an electron-poor center on the (Si-O-)Mn-O bond to adsorb a large amount of CH3SH accompanied by its own oxidative degradation. In situ Raman and in situ Fourier transform infrared (FTIR) analyses identify that catalytic ozonation over 3.0Mn-PSBA generates atomic oxygen species (AOS/*O) and reactive oxygen species (ROS/•O2-) to achieve efficient decomposition of CH3SH into CO2/SO42-. Furthermore, the electrons obtained from CH3SH in electron-poor centers are transferred to maintain the redox cycle of Mn2+/3+ → Mn4+ → Mn2+/3+ through the internal bond bridge, thus accomplishing the efficient and stable degradation of CH3SH prolonged to 180 min. Therefore, the rational design of catalysts with abundant active sites and optimized inherent activity via the EMSI effect can provide significant potential to improve catalytic performance and eliminate odorous gases.

Enhanced Catalytic Ozonation for Eliminating CH3SH via Graphene-Supported Positively Charged Atomic Pt Undergoing Pt2+/Pt4+ Redox Cycle.

Constructing catalysts with electronic metal-support interaction (EMSI) is promising for catalytic reactions. Herein, graphene-supported positively charged (Pt2+/Pt4+) atomically dispersed Pt catalysts (AD-Pt-G) with PtxC3 (x = 1, 2, and 4)-based EMSI coordination structures are achieved for boosting the catalytic ozonation for odorous CH3SH removal. A CH3SH removal efficiency of 91.5% can be obtained during catalytic ozonation using optimum 0.5AD-Pt-G within 12 h under a gas hourly space velocity of 60,000 mL h-1 g-1, whereas that of pure graphene is 40.4%. Proton transfer reaction time-of-flight mass spectrometry, in situ diffuse reflectance infrared Fourier transform spectroscopy/Raman, and electron spin resonance verify that the PtxC3 coordination structure with atomic Pt2+ sites on AD-Pt-G can activate O2 to generate peroxide species (*O2) for partial oxidation of CH3SH during the adsorption period and trigger O3 into surface atomic oxygen (*Oad), *O2, and superoxide radicals (·O2-) to accomplish a stable, high-efficiency, and deeper oxidation of CH3SH during the catalytic ozonation stage. Moreover, the results of XPS and DFT calculation imply the occurrence of Pt2+ → Pt4+ → Pt2+ recirculation on PtxC3 for AD-Pt-G to maintain the continuous catalytic ozonation for 12 h, i.e., Pt2+ species devote electrons in 5d-orbitals to activate O3, while Pt4+ species can be reduced back to Pt2+ via capturing electrons from CH3SH. This study can provide novel insights into the development of atomically dispersed Pt catalysts with a strong EMSI effect to realize excellent catalytic ozonation for air purification.

[Conversion Characteristics of Combustible Particles from Coal-fired Flue Gas in WFGD and WESP].

Monitoring of condensable particulate matter (CPM) emitted from stationary pollution sources has often been neglected. To reduce the emission of CPM, it is necessary to study its transformation rules in flue-gas cleaning devices. The results show that the wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP) have a good synergistic effect on the removal of CPM. The concentration of CPM in flue gas is higher than that of filterable particulate matter, but the concentration of total particulate matter (sum of the condensable particulate matter and filterable particulate matter) reaches ultra-low emission requirements. The organic mass concentration of CPM in the WFGD inlet and outlet is larger than that of inorganic components, which is equalized during the treatment of WESP. Based on measurements of the components and concentrations of water-soluble ions in the inorganic part of the CPM, PM0.3 can be joined during the CPM trapping process and an acid mist is generated during the condensable particulate matter formation. The acid mist is strengthened through the treatment of WFGD and WESP. The experiment results also show that SO42- is the main component of water-soluble ions in the inorganic part of CPM.