Sufficient Oxygen Vacancies Research Articles

Rod-shaped α-MnO2 electrocatalysts with high Mn3+ content for oxygen reduction reaction and Zn-air battery

Manganese dioxide (MnO2) is a potential efficient candidate for the catalysis of oxygen reduction reactions (ORR) in alkaline electrolyte. In this work, potassium permanganate (KMnO4) was reduced by silicon nanowires (SiNWs) and hydrofluoric acid (HF) to prepare α-MnO2 with a rod-like structure. The α-MnO2 prepared at 120 °C (α-MnO2-120) demonstrated excellent activity for ORR and had an oxygen reduction pathway of four-electron. In 0.1 M KOH electrolyte, it showed a large half-wave potential of 0.85 V vs. RHE and a high initial potential of 1.01 V vs. RHE. The diffusion-limiting current of α-MnO2-120 catalyst (7.0 mA cm−2) is also quite stable. The excellent ORR activity of α-MnO2-120 is attributed to the high Mn3+ content and sufficient oxygen vacancies. In addition, the zinc-air battery using the α-MnO2-120 catalyst displays an open circuit potential of 1.27 V, a maximum power density of 240 mW cm−2 at a current density of 0.33 A cm−2 and superior stability.

Enhanced photocatalysis of Mg[sbnd]Al layered double oxide nanosheets with B,N-codoped carbon coating for tetracycline removal

MgAl layered double oxide (LDO) nanosheets were coated by B,N-codoped carbon (MA#C(B,N)) for the enhanced photocatalytic degradation of tetracycline hydrochloride (TCH) under solar light irradiation. In contrast with bare MgAl LDO and BN, MA#C(B,N) nanosheets present higher photocatalytic efficiency for TCH removal. The photocatalytic activity of obtained composites are greatly affected by B,N-codoped content, TCH concentrate, pH, and inorganic ions. The optimal MA#C(B,N)-3 exhibited excellent photocatalytic activity and durability in the visible light region, and its removal efficiency was 98.85% for 120 mg L−1 of TCH solution. B,N-codoped carbon with distorted carbon lattice is favorable for the photo-generated electrons trapping and the charge transfer, meanwhile, MgAl LDO with sufficient basic sites and oxygen vacancies can accelerate the rapid separation of charge carriers at junction interface, enhancing the photocatalytic activity of MA#C(B,N).

Iodine-doping-assisted tunable introduction of oxygen vacancies on bismuth tungstate photocatalysts for highly efficient molecular oxygen activation and pentachlorophenol mineralization

In this work, the tunable introduction of oxygen vacancies in bismuth tungstate was realized via a simple solvothermal method with the assistance of iodine doping. With the predictions afforded by theoretical calculations, the as-prepared bismuth tungstate was characterized using various techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The different concentrations of the oxygen vacancies on bismuth tungstate were found to be intensely correlated with iodine doping, which weakened the lattice oxygen bonds. Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as a result of iodine doping, the molecular oxygen activation was remarkably enhanced, thus endowing bismuth tungstate with high activity for the photocatalytic degradation of sodium pentachlorophenate. More encouraging is the total organic carbon removal rate of sodium pentachlorophenate over iodine-doped bismuth tungstate that exceeded 90% in only 2 h and was 10.6 times higher than that of the pristine bismuth tungstate under visible light irradiation. Moreover, the mechanism, through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tungstate is enhanced, was speculated based on the results of radical detection and capture experiments. This work provides a new perspective for the enhanced photocatalytic degradation of organochlorine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-doped bismuth tungstate.

Fabrication of pyramid-BiVO4/CdSe composite with controlled surface oxygen vacancies boosting efficient carriers’ separation for photocathodic protection

• A novel pyramid-BiVO 4 /CdSe photoanode with enriched oxygen vacancies was prepared. • Pyramid-BiVO 4 /CdSe heterojunction promotes solar harvesting and carrier separation. • The pyramid-BiVO 4 /CdSe photoanode exhibits superior PEC performance and stability. • The corrosion potential of 304SS coupled with 8V-BC photoanode drop 708 mV. In order to solve the bottleneck problem of weak efficiency of carriers’ separation and transfer in BiVO 4 photocatalyst, a novel pyramid-BiVO 4 with sufficient oxygen vacancies was successfully synthesized via a low-temperature solvothermal method. By adjusting solution pH and adding SDBS surfactant, the prepared samples could have a variety of controllable morphologies and exposed {0 0 1} facets, which were determined by SEM, XRD, and BET methods. XPS O1s peak and ESR signals indicated that pyramid-BiVO 4 exhibited higher oxygen vacancies concentration than others. Besides, CdSe quantum dots (QDs) were introduced to construct BiVO 4 /CdSe heterojunctions composite based photoanode to further promote solar harvesting and carrier separation. The photoelectrochemical experimental results showed that 304 stainless steel (304SS) coupled with 8V-BC photoanode showed an enhanced photocurrent density (608 μA·cm −2 ) and maximum potential drop (708 mV), which were equivalent to 5.06 times and 2.10 times that of the original BiVO 4 , respectively. Mechanism study illustrated that the ultra-high performance of the 8V-BC photoanode was attributed to the synergistic effect of enriched oxygen vacancies, exposed {0 0 1} facets, enlarged visible light absorption and larger specific surface area.

Electrospun ferric ceria nanofibers blended with MWCNTs for high-performance electrochemical detection of uric acid

In this work, ferric ceria nanofibers (FC NFs) with different iron contents were successfully fabricated through electrospinning followed by calcination at 550 °C. The resultant FC NFs were blended with multi-walled carbon nanotubes (MWCNT@FC) and utilized to modify the glassy carbon electrode (GCE) for uric acid (UA) detection. The XRD patterns revealed that FCs NFs have cubic lattice structure. The Raman and X-ray photoelectron spectroscopy (XPS) were confirmed the presence of oxygen vacancies with Fe(II)/Fe(III) and Ce(III)/Ce(IV) chemical states of the surface ions. The surface morphology was investigated through scanning electron microscopy (SEM) and particle size analysis was performed using transmissions electron microscopy (TEM). The electrochemical properties of MWCNT@FC NFs were evaluated through cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods under varied conditions. The results demonstrated the crucial effects of Ce/Fe molar ratio on the electrocatalytic performance due to the sufficient oxygen vacancies originating from the incorporation of Fe3+ ions into ceria (CeO2). Furthermore, blending with 70 wt% MWCNT (MWCNT70@FC) gave rise to a significant improvement on the electrical conductivity. The MWCNT70@FC-2 modified GCE composite with Ce/Fe molar ratio of 1:1 displayed high performance towards UA detection at 6.0 pH.The detection limit of 0.3 μM was achived with wide linear range from 0.5 μM to 500 μM. The MWCNT70@FC-2 demonstartedadequate stability and reproducibility for urice acid detection. The high selectivity and accuracy was further established for prepared MWCNT@FC-2 composite sensor by detecting UA in real biological samples. The obtained results were precise and reproducible.

Remarkably improved uniform bipolar-resistive switching performance with a NiO buffer layer in Bi2SiO5 thin-film memory devices

Orthorhombic Bi2SiO5 thin films were fabricated on Pt/Ti/SiO2/Si substrates by incorporating a NiO thin layer between Bi2SiO5 and bottom electrode. Compared with those bare Pt/Bi2SiO5/Pt devices, a remarkably improved uniformity of resistive switching parameters such as electroforming voltages, reset voltages, and a resistance ratio of low/high states was demonstrated in the Bi2SiO5 devices with an embedded NiO layer. This improvement was attributed to the formation of the partial conductive filaments resulted from sufficient oxygen vacancies at the interface. Our results provide a method for the optimization of the operation voltage control toward forefront applications in nonvolatile memory.

Boosting Efficiency and Stability of Organic Solar Cells Using Ultralow-Cost BiOCl Nanoplates as Hole Transporting Layers.

A novel nanomaterial, bismuth oxychloride nanoplates (BiOCl NPs), was first applied in organic solar cells (OSCs) as hole transporting layers (HTLs). It is worth noting that the BiOCl NPs can be facilely synthesized at ∼1/200 of the cost of the commercial PEDOT:PSS and well dissolved in green solvents. Different from the PEDOT:PSS interlayer, the deposition of BiOCl HTL is free of post-treatment at elevated temperature, which reduces device fabrication complexity. To demonstrate the universality of BiOCl in improving photovoltaic performance, OSCs containing various representative active layers were investigated. The power conversion efficiencies (PCEs) of the P3HT:PC61BM, PTB7-Th:PC71BM, and PM6:Y6-based OSCs with the BiOCl HTL boosted from 3.62, 8.78, and 15.63 to 4.24, 9.92, and 16.11%, respectively, compared to the PEDOT:PSS-based ones. It was found that the superior performances of the BiOCl-based OSCs are mainly attributed to the sufficient oxygen vacancies and improved interfacial contact. Moreover, the BiOCl-based OSCs show a much better stability than the cells with the PEDOT:PSS interfacial layer.

Oxygen vacancy defect engineering in Mn-doped CeO2 nanostructures for nitrogen oxides emission abatement

The presence of sufficient oxygen vacancy defects (OVDs) in metal oxides can be a good predictor of the selective catalytic reduction with NH3 (NH3-SCR) of nitrogen oxides. Here, Mn-doped CeO2 nanoparticles with considerable OVDs (OVDs-Mn-CeO2) were successfully synthesized by KMnO4via a facile strategy. The content of OVDs and Mn4+ significantly increased, as evidenced by characterizations. The amount of absorbed oxygen species trapped in oxygen vacancies of the OVDs-Mn-CeO2 catalyst was 31.8% higher than that in conventional Mn-CeO2, as evidenced by X-ray photoelectron spectroscopy (XPS). Furthermore, density functional theory plus U (DFT + U) calculations were performed to prepare a Mn-CeO2 material with sufficient oxygen vacancies. The catalytic NH3-SCR activity was improved by introducing the OVDs into the typical Mn-CeO2 catalyst. The OVDs-Mn-CeO2 catalyst afforded high NO conversion (＞90%) at 140–240 °C, better than that of the Pure-MnOx and traditional Mn-CeO2 catalysts. It has been suggested that surface enrichment of Mn4+ and Mn/Ce redox couples could accelerate the catalytic NH3-SCR of NOx. In situ DRIFTS revealed that bidentate nitrate and NH3 adsorbed on Lewis acid sites intermediates were produced and then consumed during the NH3-SCR reaction cycle according to a Langmuir-Hinshelwood mechanism. In particular, the intermediate of combined NH3-NO3− species over the OVDs-Mn-CeO2 catalyst with abundant oxygen vacancies might be much more activated in catalytic NH3-SCR than the intermediate of NH2- species over the Mn-CeO2 catalyst.

In situ exsolution of Co/CoOx core-shell nanoparticles on double perovskite porous nanotubular webs: A synergistically active catalyst for soot efficient oxidation

The PrBa0.5Sr0.5Co0.2Fe1.8O5+δ double perovskite porous nanotubular webs are prepared by a simple electrospinning technique following calcination. It shows better catalytic activity compared with the bulk PrBa0.5Sr0.5Co0.2Fe1.8O5+δ prepared by citrate method, due to its larger specific surface area and higher utilization of active sites. On basis of this, introducing multiple active sites is conducive to enhancing the catalytic activity. In this work, the PrBa0.5Sr0.5Co0.2Fe1.8O5+δ double perovskite porous nanotubular webs are further reduced at 750 °C in a 10% H2/N2 gas flow, which can give rise to the in situ exsolution of Co core-shell nanoparticles and obtain double active sites. Meanwhile, series of related catalysts are also prepared for comparison, and the physicochemical properties of these catalysts are studied by a lot of characterization techniques. The catalytic performance for soot combustion is evaluated by a temperature programmed oxidation test, which can simulate the soot combustion process. Turn of frequency (TOF) and activation energy (Ea) are calculated by isothermal studies to further evaluate the activity of the as-prepared catalyst. Among all the prepared catalysts, the PrBa0.5Sr0.5Co0.2Fe1.8O5+δ porous nanotubular webs after reductive treatment at 750 °C in H2 atmosphere exhibits the best catalytic activity for soot combustion, showing the lowest activation energy and the highest TOF values. Furthermore, its catalytic activity is significantly promoted compared with the bulk-type catalyst. Firstly, it may be associated with the synergistic effects of sufficient Co core-shell nanoparticles and oxygen vacancies in double perovskite functioned as active sites. Secondly, the structure of porous nanotubular webs can make full use of these active sites.

Electrospun n-p WO3/CuO heterostructure nanofibers as an efficient sarin nerve agent sensing material at room temperature

Organophosphate agents are a fatal inhibitor of acetylcholinesterase and damage nerve function. To find a suitable gas sensing material has high response and rapid response/recovery times to detect the chemical warfare agents remain a big challenge. Herein, n-p heterojunction Composite WO3/CuO nanofibers, pristine WO3 nanofibers, CuO nanofibers were successfully fabricated using a single capillary electrospinning technique and following calcination treatment. The nanostructure and chemical composition were characterized by XRD, XPS, SEM, TEM, and BET, respectively. Excellent improvements of the gas sensing performance were detected to composite WO3/CuO NFs in comparison with pristine WO3 and CuO NFs. The WO3/CuO NFs were shown an excellent selectivity toward a trace of DMMP (Dimethylmethylphosphonate, a simulant gas of sarin nerve gas) at room temperature among various VOCs. The 1D-nanocomposite structure and n-p heterojunction between CuO and WO3 crystals provided sufficient oxygen vacancies to absorb and desorb the oxygen ions and achieved a high response (19.3) toward 10 ppm DMMP at 25 °C. Composite WO3/CuO NFs shows a remarkable response (6.2) to 0.5 ppm DMMP at RT. The synthesized n-p nanocomposite WO3/CuO nanofibers promise to be an effective sarin nerve agent sensor with high performance.

All Nonmetal Resistive Random Access Memory

Traditional Resistive Random Access Memory (RRAM) is a metal-insulator-metal (MIM) structure, in which metal oxide is usually used as an insulator. The charge transport mechanism of traditional RRAM is attributed to a metallic filament inside the RRAM. In this paper, we demonstrated a novel RRAM device with no metal inside. The N+-Si/SiOx/P+-Si combination forms a N+IP+ diode structure that is different from traditional MIM RRAM. A large high-resistance/low-resistance window of 1.9 × 104 was measured at room temperature. A favorable retention memory window of 1.2 × 103 was attained for 104 s at 85 °C. The charge transport mechanism of virgin, high- and low-resistance states can be well modeled by the single Shklovskii-Efros percolation mechanism rather than the charge transport in metallic filament. X-ray photoelectron spectroscopy demonstrated that the value of x in SiOx was 0.62, which provided sufficient oxygen vacancies for set/reset RRAM functions.

Low-temperature gas nitriding of AISI 4140 steel accelerated by LaFeO3 perovskite oxide

Rare earth nitriding was considered as an effective method to accelerate the nitriding efficiency. However the catalytic mechanism was not clear due to the uncertainty of rare earth (RE) elements’ existence during nitriding. In the present work, the LaFeO3 perovskite oxide was attempted to use as a catalyst in the gas nitriding for the first time. The effect of nitriding temperature on the microstructure and properties of the RE nitrided layer was investigated and the catalytic mechanism of the RE was discussed. The microstructure, phase composition and microhardness profiles of nitrided layers were characterized by the optical microscope, X-ray diffraction and micro-hardness tester, respectively. The corrosion resistance of nitrided layers was tested by the potentiodynamic polarization technique. Pin-on-disc tribometer were applied to evaluate the wear property. The X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy dispersive X-ray spectroscopy were used to identify the catalytic mechanism of the RE by analyzing the chemical state and elemental distribution on the nitrided surface. The results show that a perovskite-type oxide, LaFeO3, would form after the gas nitriding, which presents an obvious catalytic activity and increases the thickness of nitrided layers. In addition, the mechanical and corrosion properties could also be improved after nitriding with RE addition. The LaFeO3 perovskite oxide could accelerate the nitriding rate by adjusting the ratio of the adsorbed nitrogen (N) and dissolved N. On the other hand, the sufficient oxygen vacancies in the LaFeO3 oxide could provide more diffusion routes for N atoms.

Role of nitrogen functional groups and manganese oxides on the reduction of NO over modified semi-coke catalyst at low temperature

Modified semi-coke catalysts loaded melamine (M) and/or manganese oxides (MnOx) were prepared by the impregnation method for the reduction of NO at low temperature. A fixed-bed reactor, XRD, Raman and XPS were used for the catalytic activity measurement and characterization of modified semi-coke catalysts. The highest denitration rate of 5M–10Mn–ASC was 91.6% at 225 °C and kept the highest level within 200–300 °C. The results of characterization revealed the changes of nitrogen functional groups on the surface of modified semi-coke catalysts. Pyrrolic-like nitrogen (N-5) appeared on the surface of semi-coke catalysts only with M. After loading M and MnOx simultaneously, quaternary nitrogen (N–Q) appeared and the contribution of nitro type complexes (–NO2) declined sharply. During the whole reaction process, melamine as a nitrogen species source can adjust both the contribution of acidic and basic functional groups. The acidic functional groups, like C=O and N–Q, could provide active sites to adsorb NH3 and the basic functional groups, like pyridinic-like nitrogen (N-6) and N-5, could adsorb some O2 and NO. Meanwhile, the sufficient oxygen vacancies and surface chemical oxygen provided by MnOx reinforced denitration efficiency of modified semi-coke catalysts as well. Different modified conditions would result in the changing roles of nitrogen functional groups constantly, which could be beneficial to improve the denitration rate. Based on the results of catalytic activity measurements and analysis of different characterization, the possible denitrification mechanism of modified semi-coke catalysts was built.

Engineering Stable Surface Oxygen Vacancies on ZrO2 by Hydrogen-Etching Technology: An Efficient Support of Gold Catalysts for Water-Gas Shift Reaction.

The surface structure of supports is crucial to fabricate efficient supported catalysts for water-gas shift (WGS). Here, hardly reducible ZrO2 was etched with hydrogen (H), aiming to modify surface structures with sufficient stable oxygen vacancies. After deposition of gold species, the obtained khaki ZrO2-H notably improved WGS catalytic activities and stabilities in comparison to the traditional white ZrO2. The characterization results and quantitative analysis indicate that sufficient surface oxygen vacancies of ZrO2-H support give rise to more metallic Au0 species and higher microstrain, which all boost WGS catalytic activities. Furthermore, optoelectronic properties were successfully used to correlate with their WGS thermocatalytic activities, and then a modified electron flow process was proposed to understand the WGS pathway. For one thing, the introduction of surface oxygen vacancies narrowed the band gap of ZrO2 and decreased the Ohmic barrier, which facilitated the flow of "hot-electron". For another thing, the conduction band electrons can be easily trapped by oxygen vacancies of ZrO2 supports, and then these trapped electrons immediately take part in reduction of H2O to H2. Thus, the electron recombination was suppressed and the WGS catalytic activity was improved. It is worth extending H2-etching technology to improve other thermocatalytic reactions.

Oxygen Vacancy-Mediated ZnO Nanoparticle Photocatalyst for Degradation of Methylene Blue

ZnO nanoparticles (NPs) are synthesized by deoxidizing ZnO powder in a vacuum drying process. This process reduces the size of the NPs and increases the concentration of oxygen vacancies on their surfaces. ZnO NPs with sufficient oxygen vacancies are highly effective for the photodecomposition of methylene blue (MB) dye in water under ultraviolet irradiation. The MB degradation efficiency exceeds 99 percent after 50 min of light irradiation, and the catalytic property of the NPs remains stable over several complete degradation cycles. It is revealed that the concentration of oxygen vacancies on the surface, and the photocatalytic activity, are both higher for smaller NPs. Oxygen vacancies reduce the recombination rate of photo-generated charge carriers by capturing the electrons and hence, improve the efficiency of redox reactions. In addition, a smaller particle size leads to a larger specific surface area and a higher photonic efficiency for the ZnO NPs.

Hierarchical ZnO microstructures decorated with Au nanoparticles for enhanced gas sensing and photocatalytic properties

In this work, hierarchical ZnO (H-ZnO) and Au decorated hierarchical ZnO (Au-H-ZnO) microstructures have been successfully fabricated for improved gas-sensing and photocatalytic properties. Particularly, the H-ZnO microstructures are synthesized by a low temperature (60 °C) aqueous growth followed by a heat treatment process. The growth mechanism of the ZnO architecture is related to the concentration of sodium hydroxide. Gas sensing measurements reveal that the ZnO microstructures decorated with Au nanoparticles exhibited outstanding sensing properties toward acetone and ethanol, including the fast response and recovery rate, high sensitivity and low optimum working temperature, these test results are much better than that of pure ZnO sensor. Also, the UV–vis and photocatalytic measurements of the as-synthesized Au-H-ZnO microstructures displayed remarkable enhancement of photocatalytic properties. The improvement of the gas sensing and optical properties should be ascribed to the reality that the complex structure supplied a high absorption surface area and sufficient oxygen vacancies, and Au nanoparticles play the role as a catalyst to facilitate the absorption and desorption of gas molecules.

Size dependence of nanosheet BiVO4 with oxygen vacancies and exposed {0 0 1} facets on the photodegradation of oxytetracycline

A new type of promising nanosheet BiVO4 with reduced dimension, sufficient oxygen vacancies (OVs) concentration, and exposed {0 0 1} crystal facets for oxytetracycline removal were synthesized via hydrothermal method. The prepared samples were fully characterized. SEM, HR-TEM, XRD, and BET analyses determined the existence, proportion, and intensity of the exposed {0 0 1} facets on BiVO4 nanosheet. DRS and LSV were used to investigate the photoelectric properties of the samples. In addition, the XPS, solid EPR, and PL characteristics were examined to explore the change in OVs concentration of the as-synthesized BiVO4 nanosheet when compared with reported BiVO4 layer. In particular, BiVO4 lamella within the thickness of ten nanometer (tBV200) had notable relative intensity of dominant {0 0 1} facets in XRD results, thereby enhancing the internal electric field to facilitate the formation and separation of photogenerated electrons in the PL test. Nevertheless, tBV200 had a greater OVs density and a relatively larger percentage of dominant {0 0 1} facets, which could be ascribed to its remarkably enlarged BET surface area and significantly reduced size compared with the reported BiVO4 layer within the thickness of a hundred nanometer (hBV200). tBV200 showed enhanced photocurrent (1.083 mA/cm2) in the LSV test, and this value was 1.33 times higher than the larger counterpart. This finding demonstrated outstanding photoelectron conversion efficiency. The best oxytetracycline degradation ratio (95.83%) and TOC removal ratio (89.55%) were obtained with the tBV200, which involved the active species O2− and h+. The excellent photoelectric capability, photocatalytic properties, and stability of tBV200 novel catalyst could be attributed to the high number of active sites, as well as the improved formation, transportation, and collection of photogenerated charges. These advantages are related to the characteristics of reduced thickness, well-crystallized and enlarged dominant {0 0 1} facets, and enhanced OVs intensity in tBV200.

Nano Ce2O2S with Highly Enriched Oxygen-Deficient Ce3+ Sites Supported by N and S Dual-Doped Carbon as an Active Oxygen-Supply Catalyst for the Oxygen Reduction Reaction.

The design of rare-earth-metal oxide/oxysulfide catalysts with high activity and durability for the oxygen reduction reaction (ORR) is still a grand challenge at present. In this study, Ce-species (Ce2O2S/CeO2)/N, S dual-doped carbon (Ce-species/NSC) catalysts with promising oxygen storage/release capacities are prepared at different temperatures (800-1000 °C) to enhance the ORR efficiency. Mechanisms for the effects of temperature on crystalline phase transition between CeO2 and Ce2O2S and structure evolution of Ce-species/NSCs are inferred to better understand their catalytic activity. Porous Ce2O2S/NSC (950 °C) catalyst as the air-breathing cathode exhibits a maximum power density of 1087.2 mW m-2, which is higher than those of other Ce-species/NSCs and commercial Pt/C (989.13 mW m-2) in microbial fuel cells. The decline of the power density of Ce2O2S/NSC (950 °C) cathode is 8.7% after 80 days of operation, which is far lower than that of Pt/C (36.7%). Ce2O2S/NSC (950 °C) has a four-electron selectivity toward the ORR and a low charge-transfer resistance (5.49 Ω), contributing to high ORR activity and durability. The promising ORR catalytic activity of Ce2O2S/NSC (950 °C) is attributed to its high specific surface area (338.9 m2 g-1), varied active sites, high electrical conductivity, and sufficient oxygen vacancies in the Ce2O2S skeleton. The high content of Ce3+ in Ce2O2S/NSC (950 °C) facilitates the formation of more oxygen-deficient Ce3+ sites that generate more oxygen vacancies to release/store more oxygen to stabilize the available oxygen for the ORR. Thus, this study provides a new perspective for preparation and application of this new type of the ORR catalyst.

Ti2CO2MXene: a highly active and selective photocatalyst for CO2reduction

We investigated the reduction of CO2at the oxygen vacancy on MXene monolayers and Ti2CO2exhibited the best catalytic performance. Moreover, we proposed that CO and H2can introduce sufficient oxygen vacancies on O-terminated MXene.

One-step argon/nitrogen binary plasma jet irradiation of Li4Ti5O12 for stable high-rate lithium ion battery anodes

Atmospheric pressure Ar/N2 binary plasma jet irradiation has been introduced into the manufacturing process of lithium ions batteries as a facile, green and scalable post-fabrication treatment approach, which enhanced significantly the high-rate anode performance of lithium titanate (Li4Ti5O12). Main emission lines in Ar/N2 plasma measured by optical emission spectroscopy reveal that the dominant excited high-energy species in Ar/N2 plasma are N2*, N2+, N∗ and Ar∗. Sufficient oxygen vacancies have been evidenced by high resolution X-ray photoelectron spectroscopy analysis and Raman spectra. Nitrogen doping has been achieved simultaneously by the surface reaction between pristine Li4Ti5O12 particles and chemically reactive plasma species such as N∗ and N2+. The variety of Li4Ti5O12 particles on the surface of electrodes after different plasma processing time has been examined by grazing incident X-Ray diffraction. Electrochemical impedance spectra (EIS) confirm that the Ar/N2 atmospheric plasma treatment facilitates Li+ ions diffusion and reduces the internal charge-transfer resistance. The as-prepared Li4Ti5O12 anodes exhibit a superior capacity (132 mAh g−1) and excellent stability with almost no capacity decay over 100 cycles under a high C rate (10C).