Active Oxygen Species Research Articles

Enhanced stability and catalytic activity of subnanometric platinum cluster by surface doping of zirconium in CeO2

There has been a continuous effort to improve the thermal stability of subnanometric platinum (Pt) cluster (<2 nm) catalyst because Pt cluster on CeO2 support can be mobile and aggregated into nanoparticle on heating at elevated temperatures, yet this great challenge remains. In this study, a strategy is reported to improve the thermal stability of subnanometric Pt cluster by hydrothermal deposition method. Based on this method, zirconium (Zr) was precisely doped on surface of Ce0.95Zr0.05O2 by accurate control of Pt subnanometric cluster size. The surface doping of Zr is favorable for forming the Zr–O–Ce site and activating surface lattice oxygen atoms, which results in strong electronic interactions to stabilize the Pt subnanometric cluster. After high-temperature aging treatment at 1000 °C/4 h, the single atom Pt supported on CeO2 is aggregated into larger sized (>3 nm) nanoparticle. In contrast, the single atom Pt supported on Ce0.95Zr0.05O2 displays less agglomeration into subnanometric cluster with size of (1.4 ± 0.3) nm. Moreover, the CO oxide catalytic performance of Ce0.95Zr0.05O2–Pt is 26 % and 31 % higher than that of CeO2–Pt and commercial Al2O3–Pt catalysts, respectively. The experimental and density functional theory (DFT) calculations indicate that the Zr–O–Ce site and Pt subnanometric cluster interface have more defect sites and active oxygen species than CeO2–Pt interface, which activate the Mars van Krevelen (MvK) mechanism, facilitating the catalytic performance.

Controlled synthesis of CoFe@TiN composites and their rapid and efficient degradation of emerging organic pollutants: RhB as an example

Fast removal of emerging organic pollutants (EOPs) is very important for the remediation of the water environment. Therefore, in this study, we used a simple grinding-calcined assembly method to prepare CoFe@TiN metallic composite, which possessed superb peroxy disulfate (PDS) activation ability with efficient pollutant degradation and excellent cyclic utilization. Rhodamine B, a highly representative and extensively used EOP, was adopted as a model pollutant, showing that it was completely degraded within only 9 min by the CoFe@TiN/PDS. During the degradation, superoxide radical (O2•−) were the main active oxygen species responsible for pollutant degradation. Further analysis showed that the synergistic effect of Fe(III)/Co(II) effectively activated the PDS to degrade the pollutant. In practical applications, the CoFe@TiN/PDS system can resist the influence of complex matrix in water and effectively remove EOPs in real water bodies. This study comprehensively evaluates the ability of the CoFe@TiN/PDS system to remove EOPs and thus provides a new scenario or pathway for the removal of EOPs in real contaminated water bodies.

Catalytic oxidation of formaldehyde by MnOx-decorated anatase TiO2{001}: Investigation of the effect of calcination temperature on catalytic activity and reaction mechanism

The removal of indoor formaldehyde (HCHO) is crucial for human health. The design of highly catalytically active nonprecious metal catalysts has major challenges, and the use of transition metal element modification to improve the catalytic performance is an effective strategy. In this study, the active component Mn was loaded on highly active crystalline anatase TiO2{001}, and the effect of the calcination temperature on the catalytic activity was investigated. The important influence of temperature on the catalyst valence distribution, surface active oxygen species, and content was thoroughly determined by characterization techniques, such as XPS, H2-TPR, and O2-TPD. The catalytic reaction process was further analyzed by in situ infrared technology to determine the reaction intermediates and to clarify the catalyst reaction poisoning mechanism; additionally, a reasonable HCHO catalytic reaction pathway was proposed with the combination of density function theory calculations. In addition, oxygen defects on the catalyst surface were determined by EPR, and based on theoretical calculations, the oxygen defects could further reduce the reaction energy barrier through the Langmuir-Hinshelwood mechanism. By exposing specific crystal surfaces and increasing the number of oxygen defects, the catalytic activity could be effectively improved; based on these results, our study provides a concept for the subsequent development of nonprecious metal catalysts.

An insight into the role of experimental parameters in advanced oxidation process applied for pharmaceutical degradation.

The advanced oxidation process (AOP) is an efficient method to treat recalcitrance pollutants such as pharmaceutical compounds. The essential physicochemical factors in AOP experiments significantly influence the efficiency, speed, cost, and safety of byproducts of the treatment process. In this review, we collected recent articles that investigated the elimination of pharmaceutical compounds by various AOP systems in a water medium, and then we provide an overview of AOP systems, the formation mechanisms of active radicals or reactive oxygen species (ROS), and their detection methods. Then, we discussed the role of the main physicochemical parameters (pH, chemical interference, temperature, catalyst, pollutant concentration, and oxidant concentration) in a critical way. We gained insight into the most frequent scenarios for the proper and improper physicochemical parameters for the degradation of pharmaceutical compounds. Also, we mentioned the main factors that restrict the application of AOP systems in a commercial way. We demonstrated that a proper adjustment of AOP experimental parameters resulted in promoting the treatment performance, decreasing the treatment cost and the treatment operation time, increasing the safeness of the system products, and improving the reaction stoichiometric efficiency. The outcomes of this review will be beneficial for future AOP applicants to improve the pharmaceutical compound treatment by providing a deeper understanding of the role of the parameters. In addition, the proper application of physicochemical parameters in AOP systems acts to track the sustainable development goals (SDGs).

BNQDs sensitized in-situ growth SnO2 nanotube arrays for enhancing the gas sensing performances to isopropanol

Isopropanol possessed enormous significance across various application fields from industry to healthcare. Detecting isopropanol was essential in leak detection and diagnosis of disease because it can assist diagnose of lung cancer and guarantee safety in industrial environment via discerning potential leaks. In this research, a simple hydrothermal method and subsequent sacrificial template strategy were used to fabricate in-situ growth SnO2 nanotube arrays (SnO2NTs). Next, SnO2NTs was decorated with boron nitride quantum dots (BNQDs) in order to enhance the gas-sensing performances of the SnO2NTs. The BN/12-SnO2NTs exhibited the highest response (s = Ra/Rg) of up to 7.9 for 100ppm IPA, which was 2.7 times that of the 12-SnO2NTs. The response and recovery times of the SnO2NTs-based sensor were around 10 s and 8 s, respectively. The optimal working temperature of BN-SnO2NTs was 260 ℃, which was significantly lower than that of the pure SnO2NTs sensor (320 ℃). The improved sensing performances were largely attributed to the sensitization effects of BNQDs and the one-dimensional hollow structure of SnO2NTs, which brought about the generation of more oxygen-active species on the surface of BN-SnO2NTs and a significant decrease in the activation energy of the redox reaction.

Oxygen-containing functional groups of activated carbon fibers as efficient oxygen transfer channels for H2S catalytic oxidation at room temperature

Activated carbon fibers (ACFs) with different activation degrees were developed by KOH activation method. And then, series of Na2CO3 loaded ACF catalysts were prepared and tested for H2S catalytic oxidation at room temperature. Among them, Na/ACF-8 presented the highest saturation sulfur capacity (1.22 gH2S/g). Importantly, it was found that COOH, COC/COH and COOCO were the main active oxygen species, and acted as oxygen transfer channels during the reaction. The reaction process mainly involved the dissociation of H2S, the reaction of HS− with C-O bond containing groups to form C-S bonds and sulfur-containing products. Moreover, the oxygen-containing functional groups were just responsible for water generation and the superoxide radical (O2•−) was responsible for SS bond oxidation. The O2•− was activated by ring carbon defects for Na/ACF-6 and Na/ACF-8 catalysts. And the ring carbon defects and ultramicropores were jointly responsible for the activation of O2•− for Na/ACF-2 and Na/ACF-4 catalysts.

Electrochemical oxidation of low concentrated tetracycline (TC) in aqueous solution: Operation optimization, degradation mechanisms, and detoxification efficiency

The three-dimensional electrode (3DE) process has attracted much attention due to its high efficiency in treating hard-to-degrade organic pollutants. In this work, an efficient removal of low-concentration tetracycline (TC) from aqueous solution was achieved using a 3DE reactor equipped with IrO2-RuO2-Ti anode and granular activated carbon (GAC). In addition, the reliable response surface model (RSM) indicates that maintaining a current density of 12.5 mA/cm2 led to effective TC degradation (≥ 96%) within two hours. After verification, •OH and •O2− were identified as the primary active oxygen species in the 3DE system and the addition of particle electrodes significantly enhanced the system's ability to generate •O2−. Additionally, we proposed the complete degradation pathway for TC in the 3DE system, utilizing LC-MS and DFT calculations. Notably, the 3DE system demonstrates superior detoxification efficiency. Many highly toxic intermediates detoxify into minimal amounts of less toxic substances after degradation and exhibit a growth-promoting ability for mung beans comparable to that of pure water. Meanwhile, the outstanding universality, stability, and cost-effectiveness of 3DE systems also contribute to its extensive application prospects. The study presents an efficient, cost-effective, and viable process scheme for removing low-concentration TC from aqueous solutions.

Air-Promoted Light-Driven Hydrogen Production from Bioethanol over Core/Shell Cr2O3@GaN Nanoarchitecture.

Light-driven hydrogen production from biomass derivatives offers a path towards carbon neutrality. It is often however operated with the limitations of sluggish kinetics and severe coking. Herein, a disruptive air-promoted strategy is explored for efficient and durable light-driven hydrogen production from ethanol over a core/shell Cr2O3@GaN nanoarchitecture. The correlative computational and experimental investigations show ethanol is energetically favorable to be adsorbed on the Cr2O3@GaN interface, followed by dehydrogenation toward acetaldehyde and protons by photoexcited holes. The released protons are then consumed for H2 evolution by photogenerated electrons. Afterward, O2 can be evolved into active oxygen species and promote the deprotonation and C-C cleavage of the key C2 intermediate, thus significantly lowering the reaction energy barrier of hydrogen evolution and removing the carbon residual with inhibited overoxidation. Consequently, hydrogen is produced at a high rate of 76.9 mole H2 per gram Cr2O3@GaN per hour by only feeding ethanol, air, and light, leading to the achievement of a turnover number of 266,943,000 mole H2 per mole Cr2O3 over a long-term operation of 180 hours. Notably, an unprecedented light-to-hydrogen efficiency of 17.6 % is achieved under concentrated light illumination. The simultaneous generation of aldehyde from ethanol dehydrogenation enables the process more economically promising.

Air‐Promoted Light‐Driven Hydrogen Production from Bioethanol over Core/Shell Cr2O3@GaN Nanoarchitecture

AbstractLight‐driven hydrogen production from biomass derivatives offers a path towards carbon neutrality. It is often however operated with the limitations of sluggish kinetics and severe coking. Herein, a disruptive air‐promoted strategy is explored for efficient and durable light‐driven hydrogen production from ethanol over a core/shell Cr2O3@GaN nanoarchitecture. The correlative computational and experimental investigations show ethanol is energetically favorable to be adsorbed on the Cr2O3@GaN interface, followed by dehydrogenation toward acetaldehyde and protons by photoexcited holes. The released protons are then consumed for H2 evolution by photogenerated electrons. Afterward, O2 can be evolved into active oxygen species and promote the deprotonation and C−C cleavage of the key C2 intermediate, thus significantly lowering the reaction energy barrier of hydrogen evolution and removing the carbon residual with inhibited overoxidation. Consequently, hydrogen is produced at a high rate of 76.9 mole H2 per gram Cr2O3@GaN per hour by only feeding ethanol, air, and light, leading to the achievement of a turnover number of 266,943,000 mole H2 per mole Cr2O3 over a long‐term operation of 180 hours. Notably, an unprecedented light‐to‐hydrogen efficiency of 17.6 % is achieved under concentrated light illumination. The simultaneous generation of aldehyde from ethanol dehydrogenation enables the process more economically promising.

Modulating the steric effect over high-index facet of MnOx catalysts to enhance toluene oxidation

Engineering surface structures of metal-oxide catalysts are of utmost significance for boosting their catalytic performances. In this work, we reported the high-index (310) facets catalysts (MnOx-AAUS) with oxygen vacancies for VOCs degradation, which was synthesized via an ultrasonic-assisted redox precipitation process. Interestingly, the excellent catalytic performance of MnOx-AAUS catalysts was due to the steric effect between high-index facet with reactants and the simultaneous adsorption-activation of toluene and gaseous oxygen on the high-index (310) facets with oxygen vacancies. The T90% value of the (310) facets catalysts (600 ppm toluene, GHSV = 60,000 mL/g·h, 21 % O2/N2) was significantly lower than that of the previous (001) facets catalysts. Density functional theory (DFT) calculations, along with in-situ FT-IR spectra, revealed that the tilted adsorption configuration of toluene was conducive to simultaneous reaction with the surrounding activated oxygen species. Such the adsorption configuration of toluene/oxygen contributed to the substantially enhanced catalytic activity of the MnOx-AAUS catalyst for VOCs oxidation. This work provides new insights into the roles of high-index facets with oxygen vacancies of MnOx catalysts in the toluene oxidation and paves new avenues for the rational design of highly efficient catalysts for oxidation reactions.

Application insights of environmental catalysts: Synergistic effects of cellulose-based porogens and catalytic metal sites in toluene catalytic oxidation

Utilizing environmentally-friendly bacterial cellulose as a scaffold, a highly porous, layered OA-BC catalyst was synthesized through an enhanced sol-gel process. This catalyst demonstrated exceptional performance in the oxidation of toluene, outperforming conventional alternatives that utilize chemical porogens. The OA-BC catalyst efficiently degrades toluene at 220℃ with high stability and hydrophobicity, indicating resistance to deactivation. Its superior activity is due to increased oxygen vacancies, enhanced metal oxide cooperation, and a layered porous structure, which together enhance active oxygen species and oxygen diffusion. Calcination of the OA-BC catalyst results in molecular cleavage and formation of small aggregates, increasing hydroxyl groups that stabilize Cu and Ce centers, enhancing toluene-oxygen reactions. In-situ infrared and X-ray photoelectron spectroscopy confirm stable monodentate Cu+ ligands, contributing to its high catalytic activity. This study introduces a novel approach by employing bacterial cellulose as a template for synthesizing a porous stratified OA-BC catalyst, demonstrating superior performance in toluene oxidation. The efficacy of catalyst results from a tripartite synergy involving the stratified porous architecture, the stabilizing effect of Cu+-coordinating ligands and hydroxyl groups, and the interplay of hydroxyl electron donors and acceptors, shedding light on environmentally benign catalyst development.

Tailored Exfoliation of Polymeric Carbon Nitride for Photocatalytic H2O2 Production and CH4 Valorization Mediated by O2 Activation.

The exfoliation of bulk C3N4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation-decomposition (NID) strategy that is effective in peeling off BCN into few-layer C3N4 (fl-CN) with tailored thickness down to bi-layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl-CN, which is conducive to O2 adsorption and hence relevant chemical processes. In photocatalytic O2 reduction under visible light irradiation, the H2O2 production rate over the optimal fl-CN-530 catalyst is 952 μmol g-1 h-1, which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH4 can be photocatalytically oxidized by on-site formed H2O2 and active oxygen species to generate value-added C1 oxygenates with high selectivity of 99.2 % and record-high production rate of 1893 μmol g-1 h-1 among the metal-free C3N4-based photocatalysts.

Tailored Exfoliation of Polymeric Carbon Nitride for Photocatalytic H2O2 Production and CH4 Valorization Mediated by O2 Activation

AbstractThe exfoliation of bulk C3N4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation‐decomposition (NID) strategy that is effective in peeling off BCN into few‐layer C3N4 (fl‐CN) with tailored thickness down to bi‐layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl‐CN, which is conducive to O2 adsorption and hence relevant chemical processes. In photocatalytic O2 reduction under visible light irradiation, the H2O2 production rate over the optimal fl‐CN‐530 catalyst is 952 μmol g−1 h−1, which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH4 can be photocatalytically oxidized by on‐site formed H2O2 and active oxygen species to generate value‐added C1 oxygenates with high selectivity of 99.2 % and record‐high production rate of 1893 μmol g−1 h−1 among the metal‐free C3N4‐based photocatalysts.

A novel CeO2 nanowire catalyst prepared by the freeze-drying method with significantly improved catalytic performance for toluene oxidation

A wire like CeO2 catalyst (CeO2-w) was obtained after the calcination of the precursor at 400 °C, which was prepared by the freeze-drying method for the first time. It shows good performance for catalytic oxidation of toluene with T90 of 220 °C, which is much better than the CeO2 catalysts with other structures prepared by the different methods. The good performance of CeO2-w is due to the bigger pore volume, more active oxygen species, more oxygen vacancies, better low temperature reducibility, higher surface area normalized reaction rates and lower Ea value. Additionally, the CeO2-w catalyst exhibits good water resistance and catalyst stability. In situ DRIFTS indicates the catalytic oxidation of toluene on CeO2-w undergoes the progress of toluene → benzaldehyde → benzoic acid → maleic acid → CO2 and H2O. This work affords a new idea to prepare high active CeO2 nanowire catalysts for catalytic oxidation of toluene, and open an efficient way for the construction of CeO2 based composite catalysts for VOCs degradation.

Non-thermal plasma mitigation of low concentration of air pollutants: removal of isopropyl alcohol using transition metal-oxide integration.

The present work studied the decomposition of isopropyl alcohol (IPA), widely used in chemical industries and households, in a packed-bed dielectric barrier discharge (DBD) plasma reactor. Metal oxide (MOx) coated on γ-Al2O3 (M = Cu, Mn, Co) was utilized for packing. The plasma-packed mode was a likely alternative to the conventional removal techniques, as it aids the conversion of dilute concentrations of IPA to CO and CO2 at ambient conditions (room temperature and atmospheric pressure). The mean electron energy calculations suggest that electrons with higher energy are generated when the discharge zone is packed with catalysts. When comparing IPA conversion (input concentration of 25ppm) for no packing mode and MOx/γ-Al2O3 coupled plasma mode, the latter method enhances conversion to greater than 90% at an applied voltage of 18kV. Also, MOx/γ-Al2O3 showed the highest selectivity to CO2 (70%) compared to plasma-only mode (45%). The metal-oxide layer provides the necessary catalytic surface facilitating the oxidation of IPA to COx through active oxygen species or the interaction of surface hydroxyl groups. The use of MOx/γ-Al2O3 resulted in about 90% carbon balance and reduced ozone generation, demonstrating the significance of integrating metal oxide to achieve efficient conversion and maximal selectivity towards the desired products.

Unraveling the atomic interdiffusion mechanism of NiFe2O4 oxygen carriers during chemical looping CO2 conversion

AbstractBy employing metal oxides as oxygen carriers, chemical looping demonstrates its effectiveness in transferring oxygen between reduction and oxidation environments to partially oxidize fuels into syngas and convert CO2 into CO. Generally, NiFe2O4 oxygen carriers have demonstrated remarkable efficiency in chemical looping CO2 conversion. Nevertheless, the intricate process of atomic migration and evolution within the internal structure of bimetallic oxygen carriers during continuous high‐temperature redox cycling remains unclear. Consequently, the lack of a fundamental understanding of the complex ionic migration and oxygen transfer associated with energy conversion processes hampers the design of high‐performance oxygen carriers. Thus, in this study, we employed in situ characterization techniques and theoretical calculations to investigate the ion migration behavior and structural evolution in the bulk of NiFe2O4 oxygen carriers during H2 reduction and CO2/lab air oxidation cycles. We discovered that during the H2 reduction step, lattice oxygen rapidly migrates to vacancy layers to replenish consumed active oxygen species, while Ni leaches from the material and migrates to the surface. During the CO2 splitting step, Ni migrates toward the core of the bimetallic oxygen carrier, forming Fe–Ni alloys. During the air oxidation step, Fe–Ni migrates outward, creating a hollow structure owing to the Kirkendall effect triggered by the swift transfer of lattice oxygen. The metal atom migration paths depend on the oxygen transfer rates. These discoveries highlight the significance of regulating the release–recovery rate of lattice oxygen to uphold the structures and reactivity of oxygen carriers. This work offers a comprehensive understanding of the oxidation/reduction‐driven atomic interdiffusion behavior of bimetallic oxygen carriers.

Highly efficient supported bimetallic Au‐Pd catalysts for oxidative esterification of methacrolein to methyl methacrylate

AbstractAu‐Pd alloy particles supported on TiO2 were synthesized by the sol‐immobilized method and their confirmation was achieved through transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) mapping. The samples were subjected to oxidative esterification of methacrolein with methanol to methyl methacrylate (MMA). Notably, a remarkable enhancement of catalytic performance was found in the presence of Pd. Among the samples tested, the sample Au0.25Pd0.75/TiO2 exhibited the highest catalytic performance. The interaction between Au and Pd demonstrated a synergistic effect, with Pd contributing to the stability of Au nanoparticles and strengthening the production of active oxygen species, which facilitated the efficient removal of hydrogen from intermediate hemiacetal. Furthermore, a probable reaction mechanism was proposed to explain these observations.

Liposome encapsulated polydopamine nanoparticles: Enhancing ferroptosis and activating hypoxia prodrug activity

The short lifespan of active oxygen species and depressed O2 level during ferroptosis treatment in tumor cells weaken ferroptosis therapy. How to improve the utilization efficiency of active oxygen species generated in real time is pivotal for anticancer treatment. Herein, the tirapazamine (TPZ) loaded polydopamine-Fe nanoparticles (PDA-Fe-TPZ) was modified with unsaturated liposome (Lip), which was constructed to overcome the drawbacks of traditional ferroptosis therapy. The Lip@PDA-Fe-TPZ nanoliposomes can react with H2O2 to produce •OH by Fenton reaction, which then attacks Lip and transforms into radical intermediate (L•) and phospholipid peroxide radical (LOO•) to avoid the annihilation of •OH. The introduced Lip enhances lipid peroxidation and promotes oxygen consumption, resulting in increased hypoxia at tumor site. The introduced TPZ can be triggered by reductase in tumor cells under hypoxia, which can reduce to transient oxidative free radicals by reductase enzymes and destroy the structure of the surrounding biomacromolecules, thus achieving the synergistic treatment of ferroptosis and chemotherapy. In this work, we organically combined enhanced ferrroptosis with hypoxic activated chemotherapy to achieve efficient and specific tumor killing effect, which can sever as a promising treatment of cancer in the future.

Detailed Insight into Photocatalytic Inactivation of Pathogenic Bacteria in the Presence of Visible-Light-Active Multicomponent Photocatalysts.

The use of heterogeneous photocatalysis in biologically contaminated water purification processes still requires the development of materials active in visible light, preferably in the form of thin films. Herein, we report nanotube structures made of TiO2/Ag2O/Au0, TiO2/Ag2O/PtOx, TiO2/Cu2O/Au0, and TiO2/Cu2O/PtOx obtained via one-step anodic oxidation of the titanium-based alloys (Ti94Ag5Au1, Ti94Cu5Pt1, Ti94Cu5Au1, and Ti94Ag5Pt1) possessing high visible light activity in the inactivation process of methicillin-susceptible S. aureus and other pathogenic bacteria-E. coli, Clostridium sp., and K. oxytoca. In the samples made from Ti-based alloys, metal/metal oxide nanoparticles were formed, which were located on the surface and inside the walls of the NTs. The obtained results showed that oxygen species produced at the surface of irradiated photocatalysts and the presence of copper and silver species in the photoactive layers both contributed to the inactivation of bacteria. Photocatalytic inactivation of E. coli, S. aureus, and Clostridium sp. was confirmed via TEM imaging of bacterium cell destruction and the detection of CO2 as a result of bacteria cell mineralization for the most active sample. These results suggest that the membrane ruptures as a result of the attack of active oxygen species, and then, both the membrane and the contents are mineralized to CO2.

Regulation of phase composition and oxygen vacancy in hydrothermally synthesized NaNbO3 nanowire and its enhanced piezocatalytic activity for antibiotic elimination

Piezocatalysis based on piezoelectricity has shown potential for environmental remediation and production of clean energy, which, however, cannot meet the standard of practical application due to its insufficiency. Herein, we successfully regulated phase composition (monoclinic, orthogonal and amorphous) in NaNbO3 nanowire through controlling the annealing temperature and time, where the decreased structural symmetry at the two-phase interface improved the piezoelectricity and meanwhile the increased oxygen vacancies in amorphous structure acted as active sites to promote charge separation and oxygen adsorption. As a result, the optimized NaNbO3 sample annealed under 350 °C for 2 h presented much higher piezocatalytic activity for antibiotic degradation than the pristine NaNbO3. In detail, the effects of pH, antibiotic concentration, antibiotic type and reusability on the piezocatalytic performance were systematically studied. The enhanced piezocatalytic activity of the annealed NaNbO3 was revealed through testing piezoelectric coefficient, surface potential, piezoelectric current response and generation rate of active oxygen species, and therefore a possible piezocatalytic mechanism was proposed. Based on the determined intermediate products in the antibiotic degradation process, the reasonable degradation pathway was suggested.