Rich Oxygen Vacancies Research Articles

Al/Ca-doped CuFe2O4 prepared from waste printed circuit boards as a magnetic peroxymonosulfate activator for the degradation of organic pollutants

Cu-containing heterogeneous catalysts are being increasingly used to activate peroxymonosulfate (PMS) and remove organic pollutants from wastewater. However, expensive raw materials and limited metal resources restrict the practical applications of these catalysts. In this study, waste printed circuit boards (PCBs), a typical Cu-rich electronic waste, were used to prepare Al/Ca-doped CuFe2O4 (PCBs-CuFe2O4) with the assistance of Fe3+. The obtained PCBs-CuFe2O4, doped with the catalytically inert metals Al and Ca, possessed abundant porous structures, high specific surface areas, rich surface oxygen vacancies, and excellent magnetic properties. Despite its relatively poor purity and crystallinity compared to those of CuFe2O4 prepared using commercial chemicals, PCBs-CuFe2O4 exhibited superior performance in reactive blue 19 (RB19) degradation by activating PMS. Additionally, the PCBs-CuFe2O4/PMS system exhibited strong resistance to pH and water matrices, confirming the practical application of PCBs-CuFe2O4 for the elimination of organic pollutants in wastewater. Furthermore, the results of electrochemical measurements, quenching experiments, and electron paramagnetic resonance analysis revealed that 1O2 plays an important role in the degradation of RB19. The Cu(I)/Cu(II), Fe(II)/Fe(III), and OV of PCBs-CuFe2O4 dominate the activation of PMS. Thus, this study presents a novel strategy for reutilizing waste PCBs and eliminating organic contaminants in wastewater.

Electrochemical Activation in Vanadium Oxide with Rich Oxygen Vacancies for High-Performance Aqueous Zinc-Ion Batteries

Electrochemical Activation in Vanadium Oxide with Rich Oxygen Vacancies for High-Performance Aqueous Zinc-Ion Batteries

Ar plasma-engraved rGO/In2O3 hollow nanospheres with rich oxygen vacancies for enhanced triethylamine detection

We successfully constructed a high-performance In2O3 based triethylamine sensor using rGO combined with Ar plasma treatment (Ar-rGO/In2O3). The Ar plasma treatment and rGO doping did not cause significant changes to the crystal structure of In2O3 hollow nanospheres, but increased the content of oxygen vacancies in In2O3, while making the structure of In2O3 hollow nanospheres more porous and thin-walled. The gas sensitivity test results show that this new Ar-rGO/In2O3 based sensor has the advantages of high response (Ra/Rg = 172 to 100 ppm, 4.2 times that of pure In2O3 material), low detection limit (0.5 ppm), fast response speed (1 s), and good stability to triethylamine. It also has excellent selectivity, repeatability, and long-term stability. This work is of great significance for understanding the relationship between response and surface oxygen vacancies of sensitive materials, as well as promoting the development of new triethylamine sensors.

Oxygen vacancies-tuned BiOBr nanosheets for accelerating CO2 and Cr(VI) photoreduction

Unsatisfactory charge separation ability and insufficient active sites are the main factors leading to low efficiency for photocatalytic CO2 conversion and Cr(VI) reduction. Constructing surface defects to accelerate charge separation is an effective strategy for promoting photocatalytic process. Herein, the oxygen vacancies modulated BiOBr nanosheets were constructed by NaBH4 solution treatment. Density functional theory calculation results found that the formed oxygen vacancies would increase the electron density around Bi atoms near the oxygen vacancies, and inhibiting recombination of the photoinduced carriers. Besides, abundant oxygen vacancies can effectively enhance the adsorption of CO2 molecules. Therefore, the BiOBr with rich oxygen vacancies (BiOBr-ROV) shows higher evolution rates for CO (15.66 μmol g−1) and CH4 (0.22 μmol g−1) under irradiation of 300 W Xe lamp for 4 h compared with pristine BiOBr nanosheets (BiOBr) and BiOBr with deficient oxygen vacancies (BiOBr-DOV). The intermediate products in the CO2 reduction process have been detected by in-situ Fourier-transform infrared spectroscopy. Besides, the photodegradation activity of Cr(VI) over BiOBr-ROV is 98.65% under 80 min of irradiation, which is higher than that of BiOBr (78.01%) and BiOBr-DOV (53.67%). The work provides a new possibility to construct photocatalysts with high-performance for solar energy conversion.

In-situ exsolved ultrafine Ni nanoparticles from CeZrNiO2 solid solution for efficient photothermal catalytic CO2 reduction by CH4

CO2 reduction by CH4 (CRM) to produce fuel is of great significance for solar energy storage and eliminating greenhouse gas. Herein, the catalyst of ultrafine Ni nanoparticles supported on CeZrNiO2 solid solution (Ni@CZNO) was synthesized by the sol-gel method. High yield of H2 and CO (58.0 and 69.8 ​mmol ​min−1 ​g−1) and excellent durability (50 ​h) were achieved by photothermal catalytic CRM merely under focused light irradiation. Structural characterization and DFT calculations reveal that CZNO has rich oxygen vacancies that can adsorb and activate CO2 to produce reactive oxygen species. Oxygen species are transferred to ultrafine Ni nanoparticles through the rich Ni-CZNO interface to accelerate carbon oxidation, thereby maintaining the excellent catalytic stability of the catalyst. Moreover, the experimental results reveal that light irradiation can not only enhance the photothermal catalytic CRM activity through photothermal conversion and molecular activation, but also improve the stability by increasing the concentration of oxygen vacancies and inhibiting CO disproportionation.

Hetero-Interface Engineering on 9.0wt% CoOx-Doped CeO2 Nanorods as Electromagnetic Wave Absorber and Integrated into Multifunctional Aerogel.

Ceria (CeO2) becomes a promising candidate as electromagnetic wave absorbing materials (EWAMs) for their abundant natural source, rich oxygen vacancy, charge conversion, and electron transfer abilities. However, it remains challenging to regulate its nanoscale and atom-scale composition to optimize the absorbing performance and develop high-performance commercial devices. Herein, a facile method to large-scale synthesis CeO2@Co-x% (x = 5, 7, 9, 11, 13) series EWAMs with diverse amounts of decorated CoOx is presented. By modulating the ratio of doped CoOx, a rational hetero-interface is created in CeO2@Co-9% to enhance natural and exchange resonances, improving magnetic loss capability and optimizing impedance matching. Doped CoOx promotes the charge accumulation, interfacial polarization, and multiple scattering of the CeO2 for strengthening the EW absorption and attenuation, which display superb minimum reflective loss (RLmin) of -74.4dB with a wide effective absorbing bandwidth (EAB) of 5.26GHz. Furthermore, a dual crosslinking strategy is employed to fabricate CeO2@Co-9% into an aerogel device with integrated lightweight, heat insulation, compression resistance, and fame-retardant functions. This work presents an excellent example of large-scale fast synthesis of high-performance CeO2-based EWAMs and multiplication 3D devices.

Internal electric field promoted NCDs/BiOBr/AgBr Z-scheme heterojunction with rich oxygen vacancies for efficient photocatalytic degradation of tetracycline and reduction of Cr (VI)

It is important to prepare efficient photocatalysts for the degradation of antibiotics and heavy metals. In this study, NCDs/BiOBr/AgBr Z-scheme heterojunction photocatalysts with excellent performance were constructed. NCDs/BiOBr/AgBr form a Z-type heterojunction system with pyrrole nitrogen-doped carbon quantum dots (NCDs) as charge transfer channels. The internal electric field formed in NCDs/BiOBr/AgBr greatly facilitated electron transfer. The more easily broken Bi-O bonds were utilized in the synthesis to introduce rich oxygen vacancies (OVs) into NCDs/BiOBr/AgBr to promote molecular oxygen activation. Meanwhile, silver nanorods were reduced in the synthesis to enhance the photodegradation performance. The photocatalytic degradation of tetracycline (TC) and reduction of Cr (VI) were enhanced by about 4 and 6 times. The factors affecting the removal effects of TC and Cr (VI) were analyzed. The catalysts were also tested to have good stability and potential for application in real wastewater. The reactive oxygen species (ROS), which play a dominant role in the photodegradation of TC and Cr (VI) by NCDs/BiOBr/AgBr, were tested, and a possible photocatalytic mechanism was proposed.

Fe induced geometric/electronic structure engineering in YSZ nanosheets for enhanced electrocatalytic nitrogen reduction reactions

Constructing 2D geometric structure and optimize electronic structure of transition metal oxide have been demonstrated to be effective strategy to reinforce its electrochemical dinitrogen reduction reaction (NRR) performances. But combining these two advantages into metal oxide based electrocatalyst simultaneously to achieve synergic effects remains one technological challenge but very significant. Here, a self-sacrificing template coupling with Fe doped strategy were proposed to optimize the geometric and electronic structure of Zr-based electrocatalyst. Experimental results revealed that the optimal sample 2Fe-YSZ was endowed with uniform 2D heterostructures, rich oxygen vacancy and increased electronic density, which induced by the framework Fe element. These traits thus confer the 2Fe-YSZ produced through extensive exposure to extra active sites, significantly boosting the absorption and activation of N2 molecules. And the DFT calculation further validates the promotive effect of framework Fe. As expected, in the electrocatalytic NRR test, 2Fe-YSZ demonstrated high Faradaic efficiency (38.89 %) and NH3 yield rate (19.58 μg h−1 mg−1) at − 0.5 V in 0.1 M HCl, comparable to most Zr-based electrocatalytic materials for ambient NRR. This geometric/electronic structure engineering strategy could provide an idea the rational design of efficient NRR catalysts.

Alumina supported platinum-ceria catalyst for reverse water gas shift reaction

The activation of CO2 molecules is a fundamental step for their effective utilization. Constructing high-density oxygen vacancies on the surface of reducible oxides is pivotal for the activation of CO2. In this work, we prepared a series of 0.5PtxCe/Al2O3 (x = 1, 5, 10, or 20) catalysts with varying Ce loading and 0.5 wt% of Pt for the reverse water gas shift (RWGS) reaction. The size of CeO2 particle increases with Ce loading. Remarkably, the 0.5Pt5Ce/Al2O3 catalyst with an average CeO2 particle size of 5.5 nm exhibits a very high CO2 conversion rate (116.4 × 10−5 molCO2/(gcat·s)) and CO selectivity (96.1%) at 600 °C. Our experimental findings reveal that the small-size CeO2 in 0.5Pt5Ce/Al2O3 possesses a greater capacity to generate reactive oxygen vacancies, promoting the adsorption and activation of CO2. In addition, the oxygen vacancies are cyclically generated and consumed during the reaction, which contributes to the elevated catalytic performance of the catalyst. This work provides a general strategy to construct rich oxygen vacancies on CeO2 for designing high-performance catalysts in C1 chemistry.

Frustrated Lewis Pairs on Zr Single Atoms Supported N‐Doped TiO2‐x Catalysts for Electrochemical Nitrate Reduction To Ammonia

AbstractThe electrochemical reduction of nitrates (NO3RR) for ammonia synthesis at room temperature holds immense potential. One key challenge is the adsorption and activation of NO3−, along with the provision of sufficient active hydrogen to accelerate the hydrogenation process. Here, the study prepares N‐doped TiO2‐x supported by Zr single atoms (Zr‐TiON) with rich oxygen vacancies (Ov), in which unsaturated Zr (Lewis acidic, LA) sites together with oxygen atoms around Ov (Lewis base, LB) form frustrated Lewis acid‐base pairs (FLPs). At −60 mA cm−2, NH3 Faradaic efficiency reaches 94.8%, corresponding to the production rate of 663.15 µmol h−1 mgcat−1. The yield rate is up to 26.16 mmol h−1mgcat−1 at −1 A cm−2 in flowing electrolyzer. Theoretical calculations and in situ spectroscopy analysis reveal that the interaction between LA and LB sites in FLPs plays a crucial role in facilitating adsorption and activation of electron‐rich NO3− and electron‐deficient *H. The presence of enhanced FLPs significantly reduces the energy barrier for H2O dissociation, lowering it to 0.20 eV, which facilitates subsequent hydrogenation reactions. The abundance of *H accelerates hydrogenation process, thereby enhancing the activity of NO3RR. This FLP design offers a promising approach for paving the way for the development of highly efficient NO3RR catalysts.

Co/CoO heterojunction rich in oxygen vacancies introduced by O2 plasma embedded in mesoporous walls of carbon nanoboxes covered with carbon nanotubes for rechargeable zinc–air battery

AbstractHerein, Co/CoO heterojunction nanoparticles (NPs) rich in oxygen vacancies embedded in mesoporous walls of nitrogen‐doped hollow carbon nanoboxes coupled with nitrogen‐doped carbon nanotubes (P–Co/CoOV@NHCNB@NCNT) are well designed through zeolite‐imidazole framework (ZIF‐67) carbonization, chemical vapor deposition, and O2 plasma treatment. As a result, the three‐dimensional NHCNBs coupled with NCNTs and unique heterojunction with rich oxygen vacancies reduce the charge transport resistance and accelerate the catalytic reaction rate of the P–Co/CoOV@NHCNB@NCNT, and they display exceedingly good electrocatalytic performance for oxygen reduction reaction (ORR, halfwave potential [EORR, 1/2 = 0.855 V vs. reversible hydrogen electrode]) and oxygen evolution reaction (OER, overpotential (ηOER, 10 = 377 mV@10 mA cm−2), which exceeds that of the commercial Pt/C + RuO2 and most of the formerly reported electrocatalysts. Impressively, both the aqueous and flexible foldable all‐solid‐state rechargeable zinc–air batteries (ZABs) assembled with the P–Co/CoOV@NHCNB@NCNT catalyst reveal a large maximum power density and outstanding long‐term cycling stability. First‐principles density functional theory calculations show that the formation of heterojunctions and oxygen vacancies enhances conductivity, reduces reaction energy barriers, and accelerates reaction kinetics rates. This work opens up a new avenue for the facile construction of highly active, structurally stable, and cost‐effective bifunctional catalysts for ZABs.

Mesoporous and Encapsulated In2O3/Ti3C2Tx Schottky Heterojunctions for Rapid and ppb-Level NO2 Detection at Room Temperature.

Rapid and ultrasensitive detection of toxic gases at room temperature is highly desired in health protection but presents grand challenges in the sensing materials reported so far. Here, we present a gas sensor based on novel zero dimensional (0D)/two dimensional (2D) indium oxide (In2O3)/titanium carbide (Ti3C2Tx) Schottky heterostructures with a high surface area and rich oxygen vacancies for parts per billion (ppb) level nitrogen dioxide (NO2) detection at room temperature. The In2O3/Ti3C2Tx gas sensor exhibits a fast response time (4 s), good response (193.45% to 250 ppb NO2), high selectivity, and excellent cycling stability. The rich surface oxygen vacancies play the role of active sites for the adsorption of NO2 molecules, and the Schottky junctions effectively adjust the charge-transfer behavior through the conduction tunnel in the sensing material. Furthermore, In2O3 nanoparticles almost fully cover the Ti3C2Tx nanosheets which can avoid the oxidation of Ti3C2Tx, thus contributing to the good cycling stability of the sensing materials. This work sheds light on the sensing mechanism of heterojunction nanostructures and provides an efficient pathway to construct high-performance gas sensors through the rational design of active sites.

Chemically bonded Mn0.5Cd0.5S/BiOBr S-scheme photocatalyst with rich oxygen vacancies for improved photocatalytic decontamination performance

Devising exceptional S-scheme heterojunction photocatalysts utilized in annihilating pharmaceuticals and chromium contamination is significant for addressing the problem of global water pollution. In this work, a chemically bonded Mn0.5Cd0.5S/BiOBr S-scheme heterostructure with oxygen vacancies is ingeniously developed through a facile in-situ solvothermal synthesis. The designed Mn0.5Cd0.5S/BiOBr heterojunction exhibits eminently reinforced photo-activity for destruction of tetracycline hydrochloride and Cr(VI) as compared with its individual components. This substantial photo-redox performance amelioration is benefitted from the creation of an intense internal electric field (IEF) via supplying powerful driving force and migration highway by interfacial chemical bond to foster the S-scheme electron/hole disintegration. More intriguingly, the IEF at the hetero-interface drives the fast consumption of the photo-induced holes in Mn0.5Cd0.5S by the photoelectrons from BiOBr, profoundly boosting the enrichment of active photo-carriers and sparing the photo-corrosion of Mn0.5Cd0.5S. Furthermore, Mn0.5Cd0.5S/BiOBr with exceptional anti-interference property can work efficiently in real water matrices. Multiple uses of the recycled Mn0·5Cd0·5S/BiOBr evidence its prominent robustness and stability. This achievement indicates the vast potential of chemically bonded S-scheme photosystems with structural defects in the design of photo-responsive materials for effective wastewater treatment.

Electronic Modulation in Cu Doped NiCo LDH/NiCo Heterostructure for Highly Efficient Overall Water Splitting.

Layered double hydroxides (LDHs), promising bifunctional electrocatalysts for overall water splitting, are hindered by their poor conductivity and sluggish electrochemical reaction kinetics. Herein, a hierarchical Cu-doped NiCo LDH/NiCo alloy heterostructure with rich oxygen vacancies by electronic modulation is tactfully designed. It extraordinarily effectively drives both the oxygen evolution reaction (151mV@10mAcm-2) and the hydrogen evolution reaction (73mV@10mAcm-2) in an alkaline medium. As bifunctional electrodes for overall water splitting, a low cell voltage of 1.51V at 10mAcm-2 and remarkable long-term stability for 100h are achieved. The experimental and theoretical results reveal that Cu doping and NiCo alloy recombination can improve the conductivity and reaction kinetics of NiCo LDH with surface charge redistribution and reduced Gibbs free energy barriers. This work provides a new inspiration for further design and construction of nonprecious metal-based bifunctional electrocatalysts based on electronic structure modulation strategies.

Mixed-Dimensional (2D/3D/3D) Heterostructured Vanadium Oxide with Rich Oxygen Vacancies for Aqueous Zinc Ion Batteries with High Capacity and Long Cycling Life.

Heterostructure engineering and oxygen vacancy engineering are the most promising modification strategies to reinforce the Zn2+ ion storage of vanadium oxides. Herein, a rare mixed-dimensional material (VOx), composed of V2O5 (2D), V3O7 (3D), and V6O13 (3D) heterostructures, rich in oxygen vacancies, was synthesized via thermal decomposition of layered ammonium vanadate. The VOx cathode provides an exceptional discharge capacity (411 mA h g-1 at 0.1 A g-1) and superior cycling stability (the capacity retention remains close to 100% after 800 cycles at 2 A g-1) for aqueous zinc-ion batteries (AZIBs). Ex situ characterizations confirm that the byproduct Zn3V2O7(OH)2·nH2O is generated/decomposed during discharge/charge processes. Furthermore, VOx demonstrates reversible intercalation/deintercalation of H+/Zn2+ ions, enabling efficient energy storage. Remarkably, a reversible crystal-to-amorphous transformation in the V2O5 phase of VOx during charge-discharge was observed. This investigation reveals that mixed-dimensional heterostructured vanadium oxide, with abundant oxygen vacancies, serves as a highly promising electrode material for AZIBs, further advancing the comprehension of the storage mechanism within vanadium-based cathode materials.

Highly efficient peroxymonosulfate activation by Fe[sbnd]Co bimetallic modified metal-organic frameworks-derived polyhedron with enriched oxygen vacancy for tetracycline degradation

It is important to propose a targeted solution strategy for the rate-limiting step in peroxymonosulfate activation in order to promote its wider application in advanced oxidation processes. In this study, a novel catalyst with FeCo bimetal doping, rich oxygen vacancy and porous polyhedral structure was prepared by using Fe, Co-doped Metal-Organic Framework as the precursor, which strategically enhanced the abundance and stability of active sites and promoted the adsorption of contaminates and PMS molecules. The M-450 (oxygen vacancy-rich)/PMS system demonstrated superior catalytic activity and interference resistance, in which 100 % of TC could be removed within 5 min. The corresponding reaction rate constant is 1.119 min−1, which is much higher than that of M-0 (without oxygen vacancy). Moreover, a series of studies proved that nonradical pathway (singlet oxygen) accompanied free radicals (sulfate radicals and hydroxyl radicals) collectively contributed to the tetracycline degradation. This study provides new ideas for the design and improvement of the functional catalyst for application in sulfate radicals based advanced oxidation processes.

Ni modulates the coordination environment of cations in Fe3O4 to efficiently catalyze lignin depolymerization

Lignin shows great potential for sustainable production of high-quality fuels and value-added chemicals. The development of efficient and highly stable multifunctional catalysts for the depolymerization of lignin into aromatic chemicals remains a great challenge. In this work, environmentally friendly NiFe2O4 spinel catalyst characterizing with rich oxygen vacancies and porous structures was constructed by introducing Ni to modulate the coordination environment of cations in Fe3O4. Under optimal conditions, the conversion of alkali lignin catalyzed by NiFe2O4 reached 91.0%, the yield of liquid product reached 83.6% and the yield of aromatic monomer products was 31.7%. Combined results from catalyst characterization, product analysis and density functional theory calculations showed that the Lewis acidic center of the catalyst was significantly improved by the introduction of Ni, which promoted the C-O bond breaking in lignin. The Ni-O-Fe structure facilitated the adsorption of lignin substrates and reaction intermediates, which resulted in the improved depolymerization efficiency of lignin. The present work provides valuable insights into the depolymerization of lignin by spinel catalysts, and offers ideas for the future design and development of binary or even ternary spinel catalysts for the depolymerization of lignin.

A comparative study about the influence of nitrogen doping and oxygen vacancies on the photocatalytic performance of ceria

Aimed to evaluate the influence of nitrogen doping on the photocatalytic performance of ceria, three ceria samples, including nitrogen doped, rich oxygen vacancies contained and contrastive ceria were prepared from the decomposition of CeCO3OH under varied atmospheres. The physico-chemical characterizations and photocatalytic properties towards methylene blue (MB) and tetracycline (TC) of the obtained ceria were comparatively discussed in detail. Nitrogen-doped CeO2 exhibited significantly superior photocatalytic activities compared to CeO2 with rich oxygen vacancies for MB and TC photodegradation, which is mainly attributed to the significantly enhanced separation of photo-generated carriers (e−/h+). Density Functional Theory (DFT) simulation suggests that the introduced impurity states of N-doped CeO2 advance the formation and separation of e−/h+. Moreover, the electrons are simultaneously excited from N 2p and O 2p, which further elevates the carrier concentration on the nitrogen-doped CeO2, and promotes the effect of e− during the photodegradation. The obtained results offer powerful evidences for the significant enhancement on photocatalytic performances of nitrogen doped CeO2.

Rich oxygen vacancies in confined heterostructured TiO2@In2S3 hybrid for boosting solar-driven CO2 reduction

Solar energy driving CO2 reduction is a potential strategy that not only mitigates the greenhouse effect caused by high CO2 level in atmosphere, but also yields carbon chemicals/fuels at the same time. Herein, a facile way to design the heterogeneous TiO2@In2S3 hollow structures possessing robust light harvesting in both ultraviolet and visible regions is proposed and exhibits a higher generation rate of 25.35 and 1.24 μmol·g−1·h−1 for photocatalytic CO2 reduction to CO and CH4, respectively. The excellent photocatalytic catalytic performance comes from i) the confined heterostructured TiO2@In2S3 possesses a suitable band structure and a broadband-light absorbing capacity for CO2 photoreduction, ii) the rich interfaces between nanosized TiO2 and In2S3 on the shell can significantly reduce the diffusion length of carriers and enhance the utilization efficiency of photogenerated electron-hole pairs, and iii) enriched surface oxygen vacancies can provide more active sites for CO2 adsorption.

Oxygen-dependent catalytic activity of mesoporous MnCO3-based catalysts for highly effective benzene oxidation

The catalytic activities of mesoporous MnCO3-based catalysts synthesized with a simple precipitation method were investigated for the oxidation of benzene. The calcination temperature was confirmed to have significant influences on physicochemical structure and catalytic performance of samples. MnCO3-based catalysts prepared at the calcination temperature below 400 °C showed higher activity for benzene oxidation compared with manganese oxides (Mn5O8, MnxOy and MnO2), which was mainly ascribed to abundant reactive oxygen species, large specific surface areas and rich oxygen vacancies. The optimal MnCO3-300 with good durability and strong water resistance ability achieved 90% benzene conversion at 184 °C. In situ DRIFTS spectra results suggested that both lattice oxygen and adsorbed oxygen could participate in the benzene oxidation. The possible reaction pathway of benzene oxidized into CO2 and H2O was involved with phenolate, benzoquinone, maleic anhydride, maleate and acetate intermediates, where the transformation from phenolate to benzoquinone was identified as the rate-limiting step.