Surface Oxygen Vacancies Research Articles

Non-thermal plasma-catalytic ammonia synthesis over alumina-supported iron catalyst: Insights into the effect of alumina calcination temperature

Non-thermal plasma-catalytic ammonia synthesis (NTPCAS) has been regarded as a promising route to store hydrogen by utilizing renewable electricity. Alumina is a suitable support of the catalysts in NTPCAS and its properties can influence the performance of catalysts remarkably. In this study, the influence of the alumina calcination temperatures (Tc) on the catalytic performance of Fe-Al-x (x represents the value of Tc) was analyzed in a dielectric barrier discharge (DBD) reactor for NTPCAS. The results suggested that an increase in Tc transforms the alumina crystalline from γ phase to α phase. The best performance with a synthesized ammonia concentration of 11833 ppm was achieved over Fe-Al-900 with coexisting γ and θ phases of alumina under N2: H2 = 1:1 and SEI = 37.05 kJ/L conditions, which was 37 % higher than that of Fe-Al-800 with only γ phase. In addition, the larger Tc (i.e. 1100 and 1200 °C) decreased the specific surface area, increased the mean catalyst particle size, and led to the non-uniform dispersion of Fe species. The NH3-TPD and XPS studies suggested that an increase in Tc could influence the surface acidity and oxygen vacancy concentration of Fe catalysts, which were crucial to adjusting the catalytic activity for NTPCAS. This study clarifies the value of a suitable design of support of catalysts for improving NTPCAS.

Oxygen vacancy defect engineering in MoO2/Mo-doped BiOCl Ohmic junctions for enhanced photocatalytic antibiotic elimination

Vacancy defect engineering is an effective strategy for improving photocatalytic activity, but controlling surface vacancies precisely remains a challenge. In this study, MoO2/Mo doped BiOCl (Mo-BiOCl) composites enriched with oxygen vacancies (OVs) were prepared by a facile defect engineering strategy with MoO2 hollow spheres as a precursor and molybdenum sources, where the slowly released Mo4+ ions in the reaction system resulted in the tailored formation of Mo-BiOCl. The optimized MoO2/Mo-BiOCl composite (BOM-3) demonstrated significantly improved photocatalytic degradation efficiency for Tetracycline hydrochloride (TC) under visible light, with an apparent rate constant (k) 4.7 and 120 times higher than that of BiOCl and MoO2, respectively. The enhanced photocatalytic activity of BOM-3 can be attributed to the presence of abundant OVs, which extend the light response range by creating intermediate defect level from OVs. Additionally, the formation of ohmic heterojunction between Mo-BiOCl and MoO2 with close interface contacts facilitates rapid separation of interfacial charge carries and efficient migration of photogenerated electrons from Mo-BiOCl to MoO2. The possible degradation pathway of TC using BOM-3 is proposed, and toxicity evaluation indicates that most intermediates have lower toxicity than TC. This work presents a straightforward approach for improving photocatalytic antibiotic degradation through the construction of a novel Ohmic-junction with tuned surface OVs.

Regulation of surface oxygen vacancy of Cu-CeO2/TiO2 heterostructures via fast Joule heating method for enhanced CO2 electrochemical reduction

Strict control of carbon emissions is crucial for expediting the achievement of carbon neutrality. However, the current CO2RR electrocatalytic exhibits numerous shortcomings that impede the enhancement of catalytic activity. Issues such as lengthy catalyst preparation times, and high levels of precious metal content. Additionally, the aggregation of ultrafine nanoparticles contributes to a rapid deterioration in catalytic performance. Herein, a Joule-heating method is efficiently utilized to synthesize heterostructures nano-catalysts for CO2 electroreduction on carbon cloth substrates. This method takes advantage of the thermoelectric coupling of the carbon cloth to achieve carbothermal reduction, while also regulating phase composition and introduction of oxygen vacancies. The Cu-CeO2/TiO2/CC catalyst synthesized in this method showed a current density in CO2 of −32 mA·cm−2 at −1.0 V (vs. RHE). Notably, this catalyst demonstrated high CO selectivity and Faraday efficiency (FECO) of up to 82.5 % at a low potential of −0.3 V (vs. RHE). Optimal electrochemical performance is achieved at a power of 40 W. The ultra-fast temperature change process prevented the agglomeration of catalyst particles and facilitated the construction of a stable heterogeneous interface with a high oxygen vacancy concentration. In conclusion, this study presents a promising approach, particularly for the rapid preparation of low-cost, highly selective non-precious metal electrocatalysts.

Magnesium incorporation-mediated formation of oxygen vacancies in zinc ferrite for PMS activation toward effective photocatalytic 4-nitrophenol degradation

Developing highly effective heterogeneous photocatalysts for activating peroxymonosulfate (PMS) in the photodegradation of chemical effluents remains challenging. In this study, ZnFe2O4 (ZFO) nanoparticles (NPs) incorporated with different magnesium ratios were prepared using a cost-effective microwave process. The resulting Mgx:ZFO catalysts were characterized by several analysis techniques, and the effect of Mg incorporation on the photocatalytic 4-nitrophenol (4-NP) degradation was studied. The results revealed that incorporating Mg into the ZFO structure substantially improved the photocatalytic removal efficiency of 4-NP from 62 % to 89 %. Compared with pure ZFO, Mg:ZFO contained more surface oxygen vacancies (SOVs), which can facilitate the generation and transfer of photocarriers, promote PMS activation, and improve photocatalytic performance. The ZFO catalysts exhibited larger surface areas after Mg incorporation, which provided more active sites for 4-NP removal. Finally, the bandgap energy of ZFO was widened from ∼ 1.67 eV to ∼ 1.80 eV after Mg incorporation, which could reduce photocarrier recombination and result in higher photocatalytic removal efficiency.

Morphology effects of CeO2 on the performance of CaO-Cu/ CeO2 for integrated CO2 capture and conversion to CO

CeO2 support inhibits CaO sintering, and oxygen vacancy influences CO2 hydrogenation performance, making CeO2 widely applied in Integrated CO2 capture and in-situ conversion technology for reverse water–gas shift (ICCC-RWGS). Oxygen vacancy concentration was dependent on the morphology of CeO2, which would affect metal dispersion and CO2 hydrogenation conversion. However, Very little is known about the morphology effect of CeO2 on the carbon capture and in-situ hydrogenation performance of DFMs. Here, Cu/CeO2 with different CeO2 morphologies was synthesized, and high Cu dispersion was achieved on Cu/CeO2-R, exhibiting the best CO2 hydrogenation performance. Integrated Cu/CeO2 with CaO by physical mixing method, CaO-Cu/CeO2 was used to investigate the morphology effects of CeO2 on the performance of CaO-Cu/CeO2 for integrated CO2 capture and conversion to CO. CaO-Cu/CeO2-R exhibited the best capture-hydrogenation performance (CO2 conversion rate of 75 %, CO production rate of 9.72 mmol/g). The CeO2-R provided more surface oxygen vacancies, enhancing carbonate hydrogenation. The larger specific surface area and {110} crystal plane of CeO2-rod enhanced Cu dispersion, and the smaller particle size of CeO2-R enhanced its interaction with CaO, improving the cyclic stability of CaO-Cu/CeO2-R. The hydrogenation performance of CaO-Cu/CeO2 was dependent on the morphology of CeO2, providing insights into the design of high-activity metal catalytic components in ICCC-RWGS.

Boosting the lattice oxygen reactivity of perovskite electrocatalyst via less Ru substitution

The successful deployment of efficient oxygen evolution reaction (OER) electrocatalysts is highly essential for multiple clean-energy-related conversion technologies. Perovskite oxides, with compositional diversity and elemental complexity, are a classic kind of OER electrocatalysts, whereas their activity remains insufficient under the traditional adsorbate evolution mechanism (AEM) due to limited scaling relations. Herein, taking the Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite as a model system, we find a less Ru substitution strategy to boost the lattice oxygen reactivity for improved OER. The OER behavior of BSCF is greatly ameliorated as Ru doping reaches an optimal level (BSCFR0.1), delivering a lowered overpotential by 45 mV at 10 mA cm−2. Notably, such doping remarkably triggers the generation of more surface oxygen vacancies, promotes internal charge transfer, and enlarges the surface hydrophilicity, hence facilitating more lattice oxygen to participate in the surface reaction. These results demonstrate the feasibility of Ru incorporation for ameliorating the OER behavior of perovskites, and such strategy can be further leveraged to design other remarkable perovskite-based OER catalytic materials.

Synergistically Photocatalytic Conversion of Two Greenhouse Gases to Liquid‐Phase Oxygenates under Anaerobic Conditions

Collaborative conversion of methane and carbon dioxide into sustainable chemicals is an appealing solution to simultaneously overcome both environmental problems and energy crisis. However, this reaction is limited to the preparation of syngas with the unfavorable feature for transportation and storage. Herein, liquid formaldehyde as product is fabricated by the collaborative conversion of methane and carbon dioxide using anatase phase titanium dioxide as photocatalyst. The productivity reaches 14.65 mmol g−1 with 88.32% selectivity. In situ diffuse reflectance Fourier transform infrared spectroscopy, isotope testes, and theoretical calculation clarify that the photoexcited holes and electrons engage into methane oxidation and carbon dioxide reduction over anatase using surface hydroxyl species and oxygen vacancy as active sites, respectively. The consumption of surface hydroxyl species on methane oxidation promotes the oxygen vacancy formation for carbon dioxide adsorption, mutually the carbon dioxide provides the oxygen atom for surface hydroxyl species facilitating methane oxidation. The consumption of photoelectrons and photoholes on carbon dioxide reduction and methane oxidation balances the number of photogenerated carriers and ensures the catalytic system stability. In this work, the avenue is broadened toward the co‐conversion of greenhouse gas into desirable chemical products in a sustainable way.

Dual structure cobalt sites on surface hydroxyl and oxygen vacancy of BiOCl for cooperative CO2 reduction and tetracycline oxidation

Metal ion cocatalysts have huge prospect for photocatalytic CO2 reduction coupled with organic decomposition because of their cost effectiveness and abundant active sites. Herein, we exploit a defect−group oriented tactic to induce dual−structured Co sites on BiOCl with rich surface hydroxyls (OHs) and oxygen vacancies (OVs) (labeled as BiO1−xCl−OH), in which the surface OHs and OVs acted as anchoring points to anchor Co2+ ions. Density functional theory calculations manifested that surface OHs anchored Co2+ ions via hydrogen bonding to produce tight OH−Co sites, meanwhile, surface OVs with unsaturated metal sites and unpaired electrons captured Co2+ ions through chemical bonding to form close−knit OV−Co site. The as−generated OV−Co and OH−Co site served as reductive and oxidative cocatalyst for CO2 reduction and tetracycline oxidation, respectively, thereby achieving high−efficiency redox activity. This work provided a novel strategy to devise progressive dual functional metal ions cocatalysts for high−efficiency CO2 reduction and organic pollutants oxidation.

Promoting surface lattice oxygen and oxygen vacancy of CeO2 for photothermal methane dry reforming over Ni/CeO2 catalysts

The ever-increasing concentrations of CH4 and CO2 result in the greenhouse effect around the world. It’s meaningful to transform the gases for environment protection. In this work, we studied photothermal methane dry reforming over Ni/CeO2 catalysts by shaping CeO2 to nanorods and nanosheets, converting the greenhouse gases to syngas and trying to resolve challenges of Ni sintering and carbon deposition in the reaction. Through characterizations of physicochemical and optical properties, the surface lattice oxygen and oxygen vacancy were verified being more promoted on the nanorods catalysts than on the nanosheets catalysts, giving the greater reforming performance. The irradiation of visible-light accelerated CH4/CO2 rates, which was originated from that the photoelectrons reduced CO2 and the holes oxidized CHx. The oxygen vacancy strengthened metal-support interaction limiting Ni sintering, and the surface lattice oxygen gasified carbon precursors decreasing carbon deposition. The synergism between thermocatalysis and photocatalysis on the optimized 5Ni/CeO2 nanorod catalyst contributed to CH4 and CO2 rates up to 204 μmol/(gcats) and 245 μmol/(gcats), respectively, at 973 K, and carbon deposition less than 0.5 wt%. These were much superior to most reported performance. The work provided a novel photothermal approach for significantly decreasing carbon deposition in methane dry reforming.

Rapid oxygen atom capture on perovskite surface boosting the activity and durability of cathode for solid oxide fuel cells

The content and distribution of surface oxygen vacancies are crucial for the oxygen reduction reaction (ORR) activity of solid oxide fuel cell (SOFC) cathodes. Therefore, a facile and rapid oxygen atom capture strategy is developed to modulate the surface oxygen vacancies of the cathode. By controlling the duration of NaBH4 solution reduction, precise modulation of the surface oxygen vacancies of NdBa0.5Sr0.5Co2O5+δ (NBSC) is achieved. Consequently, the processes of oxygen adsorption, dissociation, and diffusion on the surface of the NBSC cathode are enhanced. The research findings demonstrate that NBSC reduced for 10 min (RE-NBSC-10) exhibits optimal ORR catalytic activity and CO2 tolerance. At 800 °C, the Rp of RE-NBSC-10 decreases by 45 %, reaching 0.006 Ω‧cm2. Moreover, the maximum power density (MPD) of the RE-NBSC-10 cathode reaches 1.16 W cm−2, representing a 90.2 % improvement compared to NBSC. This research provides an efficient approach for the advancement of materials tailored for next-generation energy conversion devices.

Electrochemical reconfiguration of iron-modified Ni3S2 surface induced oxygen vacancies to immobilize sulfate for enhanced oxygen evolution reaction

There is an urgent need for highly active, durable, and low-cost electrocatalysts to overcome the shortcomings of high overpotential in the oxygen evolution reaction (OER) process. In this work, the nickel–iron hydroxysulfate rich in sulfate and oxygen vacancies (SO42−@Fe-NiOOH-Ov/NiS) is legitimately constructed. SO42−@Fe-NiOOH-Ov/NiS only requires a low overpotentials of 190 mV and 232 mV at 10 mA cm−2 and 100 mA cm−2 current densities in 1 M KOH, with excellent stability for 200 h at 100 mA cm−2 current density. In situ Raman spectroscopy and Fourier transform infrared spectroscopy demonstrated the stable adsorption of more SO42− on the surface of catalyst. Density functional theory calculations testify surface reconstruction, doped Fe and oxygen vacancies significantly reduced the adsorption energy of sulfate on the surface. More importantly, the formation of *OOH to O2 is facilitated by the highly hydrogen bonding between SO42− and *OOH, accelerating the OER process.

Exploring the Gas-Sensing Mechanism of a WO3 Nanowires-Based Sensor for Ethanol Detection by Near-Ambient Pressure XPS

The WO3 nanowires (NWs), fabricated on a commercial Al2O3-based sensor platform, underwent near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) analysis during ethanol detection. Our findings revealed challenges that may appear in utilizing NAP-XPS studies for studying a real gas sensor in operando conditions. Through NAP-XPS analysis, we explored the gas-sensing mechanisms of pristine and Pt-decorated WO3 NWs for ethanol sensing at different temperatures, demonstrating a combination of several mechanisms commonly observed in metal-oxide chemiresistors. For ethanol sensing, the primary driving force for the sensor's macroscopic electrical response at low temperatures was the adsorption of ethanol molecules. Conversely, at high temperatures, it involved the adsorption of ethoxy groups along with the reducing effect of ethanol on the WO3 surface. It is shown that the surface oxygen vacancies play a crucial role in the ethanol sensing mechanism of WO3 NWs-based gas sensors. Figure 1

Synergistic effect of grain size and surface oxygen vacancies for enhanced photoresponse properties of nanocrystalline SnO2 films

The photoresponse properties of nanocrystalline tin dioxide (SnO2) thin films with different grain sizes were systematically studied for fabricating transparent oxide-based ultraviolet (UV) photodetector. SnO2 nanoparticles were synthesized using the coprecipitation method and calcination temperatures were varied (400 °C–800 °C) to prepare SnO2 particles of different grain sizes (∼8 nm–∼42 nm). Subsequently, thin films of SnO2 nanoparticles were deposited using the spin-coating technique to fabricate UV photodetectors. The optical transparency of SnO2 thin films was improved by 10 % with the increasing grain size of the sample, while the band gap of the films was found to vary from 3.718 eV to 3.761 eV. The responsivity (Rλ) and the external quantum efficiency (EQE) of SnO2 based photodetector were noticeably large (Rλ = 200 mA/W and EQE = 90 %) in the UV range for devices with the smallest grain sizes (∼8 nm). Moreover, the same device exhibited a much faster photoresponse time (∼2 s) and a large photo-to-dark current ratio (∼103). The structural and spectroscopic studies on the SnO2 thin films revealed that the microscopic parameters like grain size, grain boundary potential, and surface oxygen vacancies play significant roles in modulating the optical properties and photoresponse of the nanocrystalline SnO2 thin films.

Control interfacial charge transfer behavior by creating surface defects on structure unit of heterojunction to drive carrier separation for enhancing photocatalytic CO2 reduction

Controlling interfacial charge transfer behavior of heterojunction is an arduous issue to efficiently drive separation of photogenerated carriers for improving the photocatalytic activity. Herein, the interface charge transfer behavior is effectively controlled by fabricating an unparalleled VO-NiWO4/PCN heterojunction that is prepared by encapsulating NiWO4 nanoparticles rich in surface oxygen vacancies (VO-NiWO4) in the mesoporous polymeric carbon nitride (PCN) nanosheets. Experimental and theoretical investigations show that, differing with the traditional p-n junction, the direction of built-in electric field between p-type NiWO4 and n-type PCN is reversed interestingly. The strongly codirectional built-in electric field is also produced between the surface defect region and inside of VO-NiWO4 besides in the space charge region, the dual drive effect of which forcefully propels interface charge transfer through triggering Z-Scheme mechanism, thus significantly improving the separation efficiency of photogenerated carriers. Moreover, the unique mesoporous encapsulation structure of VO-NiWO4/PCN heterostructure can not only afford the confinement effect to improve the reaction kinetics and specificity in the CO2 reduction to CO, but also significantly reduce mass transfer resistance of molecular diffusion towards the reaction sites. Therefore, the VO-NiWO4/PCN heterostructure demonstrates the preeminent activity, stability and reusability for photocatalytic CO2 reduction to CO reaction. The average evolution rate of CO over the optimal 10 %-VO-NiWO4/PCN composite reaches around 2.5 and 1.8 times higher than that of individual PCN and VO-NiWO4, respectively. This work contributes a fresh design approach of interface structure in the heterojunction to control charge transfer behaviors and thus improve the photocatalytic performance.

Can Subsurface Oxygen Species in Oxides Participate in Catalytic Reactions? An 17O Solid-State Nuclear Magnetic Resonance Study.

The impacts of subsurface species of catalysts on reaction processes are still under debate, largely due to a lack of characterization methods for distinguishing these species from the surface species and the bulk. By using 17O solid-state nuclear magnetic resonance (NMR) spectroscopy, which can distinguish subsurface oxygen ions in CeO2 (111) nanorods, we explore the effects of subsurface species of oxides in CO oxidation reactions. The intensities of the 17O NMR signals due to surface and subsurface oxygen ions decrease after the introduction of CO into CeO2 nanorods, with a more significant decrease observed for the latter, confirming the participation of subsurface oxygen species. Density functional theory calculations show that the reaction involves subsurface oxygen ions filling the surface oxygen vacancies created by the direct contact of surface oxygen with CO. This new approach can be extended to the study of the role of oxygen species in other catalytic reactions.

In-situ ellipsometric study of WO3–x dielectric permittivity during gasochromic colouration

The complex dielectric permittivity of tungsten oxide at all stages of its colouration in a hydrogen-rich atmosphere was retrieved from measured VIS-NIR ellipsometric spectra of WO3/Pd bilayer. The retrieval was done by fitting the spectra with the Cody-Lorentz dispersion model, and, for optical absorption features, two Gaussian functions were added. The band gap edge, the Gaussian center energies, amplitudes, spectral widths and integrals were traced as the redox reaction progressed. Analysis of obtained data provides insight into mechanism of surface and bulk oxygen vacancies formation. We discuss these peculiarities in detail and show how they do affect the optical constants of WO3–x and potential sensors’ response rates.

Enhanced photocatalysis-Fenton degradation of levofloxacin by Fe doped BiOCl microspheres with rich surface oxygen vacancies: The accelerated redox cycle of ≡Fe(III)/≡Fe(II)

The photocatalysis-Fenton process was considered as an effective water treatment method due to its superior efficiency and technical feasibility, but its application was limited by ≡Fe(III)/≡Fe(II). Herein, Fe doped BiOCl hierarchical microspheres with rich surface oxygen vacancies (Fe/BiOCl OVs) were synthesized to modulate the interface structure for efficient photocatalysis-Fenton degradation of levofloxacin (LEV). The systematic characterization analysis confirmed the existence of strong interfacial interactions, which facilitated the activation of H2O2 and the degradation of LEV. The synergism of metal deposition, OVs and surface plasmon resonance (SPR) effect of Bi contributed to the enhanced light absorption ability and suppressed carriers recombination. The LEV degradation efficiency reached 99.0% after 60-min photocatalysis-Fenton reaction. The interfacial charge transfer theory demonstrated that the presence of oxygen vacancies accelerated the redox cycle of ≡Fe(III)/≡Fe(II), which promoted the H2O2 activation to produce ·OH. The ·OH and e- played important roles during the photocatalysis-Fenton degradation of LEV, while ·O2–, 1O2 and h+ also contributed in LEV degradation. Based on density-functional theory (DFT) calculations and LC-MS analysis, four degradation pathways of LEV were proposed. The photocatalysis-Fenton degradation process of Fe/BiOCl OVs effectively reduced the toxicity of LEV, which ultimately mitigated the harmful effects of antibiotics on the environment.

Activated carbon based TiO2 nanocomposites (TiO2@AC) used simultaneous adsorption and photocatalytic oxidation for the efficient removal of Rhodamine-B (Rh–B)

The availability of fresh water is limited compared to its huge consumption. Conversely, certain industries like dyes, textiles, paper, and tanning not only consume vast quantities of fresh water, but also generate significant amounts of wastewater that poses severe threats to living organisms. The present investigation focuses on the degradation of Rhodamine-B (Rh–B) as a model pollutant by using the nanocomposite based on waste scrap tire-derived activated carbon (AC) and titanium dioxide (TiO2). These nanostructures were fabricated using wet chemistry techniques. Analysis using scanning electron microscopy (SEM) revealed that the morphology of the structures remained largely unchanged even with a concentration of 6 mg of AC. X-ray diffraction (XRD) results confirmed the successful fabrication of rutile and anatase phases of TiO2@AC nanocomposite. The XPS results confirmed the presence of AC and TiO2 in the composite. Furthermore, the optical band gap of the nanocomposites decreased up to 17.17 % and 34.57 % through direct and indirect methods respectively, owing to the varying quantity of AC used. The narrowing of optical band gap and the increased surface oxygen vacancies were caused by the successive addition of AC during the synthesis of nanocomposites. This resulted in the efficient degradation of Rhodamine-B (Rh–B) using adsorption and photocatalytic oxidation. The findings demonstrate a significant influence of AC on the TiO2 catalyst in the removal of Rh–B dye. The maximum efficiency of dye removal, reaching up to 99.14 %, was achieved with the highest concentration of AC, thus demonstrating almost complete elimination of Rh–B dye. The findings suggest that the use of waste scrap tires can be effectively applied to design efficient photocatalysts for addressing the wastewater management issues.

Modified Ta2O5-x prepared by NaBH4 reduction for enhance its photocatalytic activity

The generation of oxygen vacancies assumes a pivotal role in the photocatalytic degradation of antibiotics. Surface oxygen vacancies serve as deterrents to the recombination of photogenerated carriers, thereby augmenting photocatalytic efficiency. In this work, the NaBH4 reduction technique was adopted to introduce oxygen vacancies onto the surface of Ta2O5-x, thus enhancing its photocatalytic powers. Remarkably, the photocatalytic activity of the modified Ta2O5-x-0.5 M samples exhibited significant improvement upon treatment with NaBH4 solution at varied concentrations. Characterization of the modified Ta2O5-x samples was conducted using a suite of techniques including XRD, FT-IR, UV–vis DRS, ESR, XPS, and EPR. Notably, the EPR spectrum provided compelling evidence of the presence of oxygen vacancies, affirming their existence on the surface of the modified Ta2O5-x samples. To further corroborate the formation of oxygen vacancies, tetracycline (TC) solution was employed as a simulated pollutant, revealing a marked enhancement in visible light catalytic activity through experimental observations. The findings elucidate that the defect sites engendered by oxygen vacancies primarily enhance the efficiency of electron-hole pair separation and facilitate greater absorption of visible light, thereby amplifying photocatalytic activity. The modification of Ta2O5-x samples by NaBH4 reduction predominantly facilitates the introduction of oxygen vacancies on the surface, consequently bolstering photocatalytic performance. This exemplifies a noteworthy approach for significantly enhancing the photocatalytic activity of Ta2O5-x, providing valuable insights for future design strategies.

Surface Oxygen Vacancies and Corona Polarization of Bi4Ti3O12 Nanosheets for Synergistically Enhanced Sonopiezoelectric Therapy.

Sonopiezoelectric therapy, an ultrasound-activated piezoelectric nanomaterial for tumor treatment, has emerged as a novel alternative modality. However, the limited piezoelectric catalytic efficiency is a serious bottleneck for its practical application. Excellent piezoelectric catalysts with high piezoelectric coefficients, good deformability, large mechanical impact surface area, and abundant catalytically active sites still need to be developed urgently. In this study, the classical ferroelectric material, bismuth titanate (Bi4Ti3O12, BTO), is selected as a sonopiezoelectric sensitizer for tumor therapy. BTO generates electron-hole pairs under ultrasonic irradiation, which can react with the substrates in a sonocatalytic-driven redox reaction. Aiming to further improve the catalytic activity of BTO, modification of surface oxygen vacancies and treatment of corona polarization are envisioned in this study. Notably, modification of the surface oxygen vacancies reduces its bandgap and inhibits electron-hole recombination. Additionally, the corona polarization treatment immobilized the built-in electric field on BTO, further promoting the separation of electrons and holes. Consequently, these modifications greatly improve the sonocatalytic efficiency for in situ generation of cytotoxic ROS and CO, effectively eradicating the tumor.