Rich Oxygen Research Articles

A remarkable oxygen vacancy-rich rare earth aerogel with high activity towards electro and catalytic reduction of 5-nitroquinoline

The presence of industrial waste in ecosystems poses a significant threat to the environment and aquatic life. Hence, remediating this waste into eco-friendlier forms becomes paramount. One effective approach to addressing pollutants is through the electro-reduction or catalytic reduction of harmful substances. This study introduces an innovative solution to this issue by utilizing a mesoporous network structure of cerium aerogels enriched in oxygen vacancies (m-CeO2-xAGL). This was realized via a reverse-engineered borohydride hydrolysis method, which acts as a catalyst for the electro-reduction of 5-nitroquinoline (5-NQ). A synergistic effect between the superior mesoporous network structure, that is, the Ce3+ defect states and rich oxygen vacancies, provided a considerable improvement in the electro-reduction properties toward 5-NQ with an extremely low detection limit (7.5 nM), high sensitivity (1.72 μA μM−1 cm−2) and good linear range (0.05−10 μM & 15−110 μM). Furthermore, the proposed reduction catalyst can be employed for on-site real-time analysis of 5-NQ in agricultural water samples with good recovery. Additionally, the aerogels were tested for catalytic reduction of 5-NQ to 5-aminoquinoline (5-AQ) with NaBH4 in the presence of ultraviolet–visible (UV–vis) light. The catalytic rate constant of pristine cerium oxide (p-CeO2) and m-CeO2-xAGL were estimated to be 4.8 × 10−3 m−1 and 6.7 × 10−3 m−1, respectively. This study affirmed that the mesoporous network structure of aerogels with rich oxygen vacancies could be employed effectively for electro and catalytic reduction of 5-NQ.

Construction of hexagonal hollow rod-shaped NiCo2O4–In2O3 p-n heterojunction for low concentration formaldehyde detection

The construction of p-n heterostructures using n-type and p-type semiconductor is a very important way to enhance gas sensing performance. In this work, hexagonal rod-shaped NiCo2O4/In2O3 with larger surface area was prepared via a simple water bath approach and subsequent calcination process. The microscopic morphology characterization results show that the NiCo2O4/In2O3 composite has a hexagonal hollow rod-shaped structure, where NiCo2O4 grows in situ on the surface of In2O3, forming p-n heterojunctions. Notably, the NiCo2O4/In2O3 composites formed with 6% NiCo2O4 addition (In-NC6) at 200 °C showed the best gas sensing performance for 1 ppm formaldehyde with a response value of 9.11 and a theoretical detection limit as low as 10.83 ppb. The rich oxygen vacancies, active site and p-n heterojunction are conducive to the adsorption of formaldehyde and electron transfer. This in situ growth approach provides novel ideas and promising prospects to synthesize other p-n heterojunction materials for applying to toxic gas detection.

3D Carbon Microspheres with a Maze-Like Structure and Large Mesopore Tunnels Built From Rapid Aerosol-Confined Coherent Salt/Surfactant Templating.

Hierarchically porous carbons with tailor-made properties are essential for applications wherein rich active sites and fast mass transfer are required. Herein, a rapid aerosol-confined salt/surfactant templating approach is proposed for synthesizing hierarchically porous carbon microspheres (HPCMs) with a maze-like structure and large mesopore tunnels for high-performance tri-phase catalytic ozonation. The confined assembly in drying microdroplets is crucial for coherent salt (NaCl) and surfactant (F127) dual templating without macroscopic phase separation. The HPCMs possess tunable sizes, a maze-like structure with highly open macropores (0.3-30µm) templated from NaCl crystal arrays, large intrawall mesopore tunnels (10-45nm) templated from F127, and rich micropores (surface area >1000 m2 g-1 ) and oxygen heteroatoms originated from NaCl-confined carbonization of phenolic resin. The structure formation mechanism of the HPCMs and several influencing factors on properties are elaborated. The HPCMs exhibit superior performance in gas-liquid-solid tri-phase catalytic ozonation for oxalate degradation, owing to their hierarchical pore structure for fast mass transfer and rich defects and oxygen-containing groups (especially carbonyl) for efficient O3 activation. The reactive oxygen species responsible for oxalate degradation and the influences of several structure parameters on performance are discussed. This work may provide a platform for producing hierarchically porous materials for various applications.

Oxygen vacancies enhanced natural manganese sand activation by PMS for CBZ degradation: Intermediate toxicity and DFT calculations

The preparation of sulfate-based advanced oxidation catalysts is usually both complex and expensive. In this study, natural manganese sand enriched with oxygen vacancies was prepared by NaBH4 reduction of natural manganese sand for activating peroxymonosulfate (PMS) to remove carbamazepine (CBZ). 70% of carbamazepine was degraded at 120 min when natural manganese sand enriched with oxygen vacancies and PMS were dosed at 0.4 g/L and 0.3 g/L respectively, and the reaction rate constant of the natural manganese sand system with rich oxygen vacancies was 7 times that of the common system. The mineralization of total organic carbon (TOC) reached 41.9%. Combined EPR and radical quenching assays revealed that degradation of pollutants relied on the involvement of free radicals and non-free radicals, in which singlet oxygen was dominant. The XPS results showed that the redox cycles of Fe3+/Fe2+ and Mn4+/Mn3+/Mn2+ promoted the generation of free radicals. Density functional theory results also showed that the energy required for PMS to adsorb on natural manganese sand with many oxygen vacancies was decreased, and the OO bond was elongated, which was beneficial to the catalytic reaction. According to LC-MS and Fukui function, the degradation route of CBZ was predicted, and the toxicity of the breakdown products was calculated. The research provides a reference for introducing oxygen vacancies in natural catalysts to improve degradation performance for “green (source) to green (application)”.

An oxygen-vacancy rich ZnFe2O4/BiOI/AgI heterojunction for enhanced photocatalytic and photo-Fenton performance via double Z-scheme structure

As a bridge, BiOI nanosheets connect ZnFe2O4 nanoparticles and AgI clusters (∼300 nm) via hydrothermal-coprecipitation. A ternary composite with a double Z-type heterojunction structure is obtained through precise electronic regulation. Compared with ZnFe2O4 and ZnFe2O4/BiOI, the photo-Fenton degradation RhB of ZnFe2O4/BiOI-AgI-3 samples is obviously improved under simulated sunlight. Rich oxygen vacancies also provide more active sites for photocatalysis and photo-Fenton process. The main active specie in photo-Fenton degradation is ·OH. The existence of a double Z-heterojunction structure and Ag0 makes the electrons on the interface transfer and separate effectively. Notably, the intensity of PL luminescence ZnFe2O4/BiOI/AgI is lower than that of ZnFe2O4 and ZnFe2O4/BiOI because of reducing the recombination rate of photogenerated carriers. ZnFe2O4/BiOI/AgI composites have excellent stability of photo-Fenton degradation. Furthermore, the formation of a built-in electric field inhibits the recombination of electron-hole pairs, enhances visible light absorption, results in improving the efficiency of ternary composite materials to degrade pollutants.

Cooperation of ultrathin bowl-shaped scaffolds and oxygen vacancies promoting selective photo-oxidation of aromatic alcohols on layered oxyhalide PbBiO2Cl

Photocatalytic selective oxidation of aromatic alcohols into value-added chemicals has attracted increasing attention. Yet most processes suffer from sluggish charge kinetics, weak O2 affinity, low conversion efficiency and selectivity, which restrict their practical development. Herein, PbBiO2Cl ultrathin bowls (UBs) with rich oxygen vacancies (ROV) were initially fabricated via a combined microemulsion method and in-situ reduction process. The ultrathin bowl-shaped geometry and rich OVs effectively boost light absorption and charge separation. Theoretical results indicate the OVs on PbBiO2Cl not only generate abundant localized electrons, but also afford strong interfacial covalent bonds between O2 and OVs, which can act as atomic-level electron transfer highway and effectively promote the O2 adsorption and activation. As a result, ROV-PbBiO2Cl UBs show a 5.2-fold enhanced activity for aerobic oxidation of alcohols to aldehydes relative to PbBiO2Cl nanoplates (NPs). This work may inspire the design of more open hollow scaffolds with defect engineering for artificial photosynthesis.

Al and W co-doped NiO nanoflowers with low crystallinity and rich oxygen vacancies for high stability and selective triethylamine detection

In this work, pure NiO, Al-doped NiO, W-doped NiO and a series of Al/W co-doped NiO nanoflowers were successfully prepared through a simple solvothermal method. Various characterization methods, such as XRD, SEM, TEM, HRTEM and XPS, were used to confirm the physical and chemical properties of the sensitive materials in terms of micro-nano structures, compositions and elemental distributions. The as-obtained Al/W co-doped NiO showed a nanoflower structure with an approximate size of ∼ 200 nm. What's more, among six sensors constructed from the sensitive materials, the sensor based on 3 at% Al3+/3 at% W6+ co-doped NiO (3Al3W-NiO) achieved the highest response (Rg/Ra=112) toward 100 ppm triethylamine with a low detection limit (1 ppm) at 325 ℃. Besides, this sensor also exhibited excellent response/recovery characteristics and long-term stability. These favorable sensing performances of the 3Al/3 W co-doped NiO sensor are not only modulated by the initial resistance (Ra), but are also closely related to the large specific surface area, porous structures, low crystallinity, rich oxygen vacancies and high Ni3+/Ni2+ ratio in the composite nanomaterials.

Doping Engineering to Modulate Lattice and Electronic Structure for Enhanced Piezocatalytic Therapy and Ferroptosis.

Piezocatalytic therapy, which generates reactive oxygen species (ROS) under mechanical force, has garnered extensive attention for its use in cancer therapy owing to its deep tissue penetration depth and less O2 -dependence. However, the piezocatalytic therapeutic efficiency is limited owing to the poor piezoresponse, low separation of electron-hole pairs, and complicated tumor microenvironment (TME). Herein, a biodegradable, porous Mn-doped ZnO (Mn-ZnO)nanocluster with enhanced piezoelectric effect is constructed via doping engineering. Mn-doping not only induces lattice distortion to increase polarization but also creates rich oxygen vacancies (OV ) for suppressing the recombination of electron-hole pairs, leading to high-efficiency generation of ROS under ultrasound irradiation. Moreover, Mn-doped ZnO shows TME-responsive multienzyme-mimicking activityandglutathione (GSH) depletion ability owing to the mixed valence of Mn (II/III), further aggravating oxidative stress. Density functional theory calculations show that Mn-doping can improve the piezocatalytic performance and enzyme activity of Mn-ZnO due to the presence of OV . Benefiting from the boosting of ROS generation and GSH depletion ability, Mn-ZnO can significantly accelerate the accumulation of lipid peroxide and inactivate glutathione peroxidase 4 (GPX4) to induce ferroptosis. The work may provide new guidance for exploring novel piezoelectric sonosensitizers for tumor therapy.

Influence of La doping on the ethanol gas sensing properties of CdSnO3 micro-cubes

Metal oxides with perovskite structure have draw much attentions in the field of gas sensors because of their easy component regulation by element doping, leading the improvement of gas sensing properties. Herein, La-doped CdSnO3 micro-cubes with excellent ethanol gas sensing properties were synthesized using a co-precipitation method combined with an annealing process. The phase structure, morphology, and micro-structure of pure CdSnO3 and La doped CdSnO3 micro-cubes were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM). The influence of La doping on the gas sensing performance of CdSnO3 were investigated. The sensor response of Cd0.88La0.12SnO3 toward 100 ppm ethanol reached 115.2 at the operating temperature of 300 ºC, which was approximately 19 times higher than that of pure CdSnO3. In addition, Cd0.88La0.12SnO3 also showed fast response-recovery speed and good stability. The enhanced gas sensing properties of Cd0.88La0.12SnO3 micro-cubes were attributed to their abundant active sites, rich oxygen vacancy, and optimized internal electric field based on the analysis by X-ray photoelectron spectrometer (XPS), UV-Vis absorption characteristics (UV–vis), electron paramagnetic resonance (EPR), and ultraviolet photoelectron spectroscopy (UPS).

Efficient processing of tritiated water by using a two-stage Pd membrane reactor with Pt/TiO2 catalyst

Large amounts of tritiated water (HTO) will be produced during the operation of nuclear power plants and fusion devices, which is harmful to the environment and human due to its radioactivity and toxicity. So, the tritium concentration of tritiated water must be reduced to a very low value before discharge. Hydrogen-water isotope exchange reaction (H2 + HTO→H2O + HT) based on palladium membrane reactor has been proposed to process tritiated water. However, a comprehensive study about the influence of operation parameters on the membrane reactor performance is insufficient, which is not conducive to the design of reactor in practical application. Moreover, the commonly used Pt/Al2O3 or Ni/SiO2 catalysts are not active for tritiated water dissociation, so the catalytic activity of these catalysts is not high. In order to process tritiated water more effectively, a two-stage membrane reactor has been designed and established in this work, and Pt/TiO2 catalyst with rich oxygen vacancies is used to catalyze the hydrogen-water isotope exchange reaction for the first time. The membrane reactor performance shows an approximate linear relationship with a new combined parameter S0.5P1.5R/F2 (S is membrane area, F is water flow rate, P is vapor partial pressure, R is swamping ratio), which can be used predict the membrane performance. The isotope exchange reaction activity of Pt/TiO2 is better than that of Pt/Al2O3 due to its good ability for water dissociation and the hydrogen spillover effect. At last, a tritiated water processing experiment by using two-stage membrane reactor with Pt/TiO2 catalyst with rich oxygen vacancies has been carried out. The tritium decontamination factor reaches 40588, which is the highest experimental value so far. The results indicate that the two-stage Pd membrane reactor based on hydrogen-water isotope exchange reaction is an efficient technology for tritiated water processing.

Visible-light induced tetracycline degradation catalyzed by dual Z-scheme InVO4/CuBi2O4/BiVO4 composites: The roles of oxygen vacancies and interfacial chemical bonds

Dual Z-scheme InVO4/CuBi2O4/BiVO4 (CuInBi) composites with rich oxygen vacancies and chemical bonds at the heterojunction interfaces were fabricated, for the first time, through hydrothermal method with post annealing treatment, in which CuBi2O4 acts as a bridge to connect InVO4 and BiVO4. The as-prepared composites exhibited superior photocatalytic activity compared with the individual semiconductors. Specifically, the degradation rate of tetracycline (20 mg/L) in the presence of CuInBi-1 (1.0 g/L) was up to 5.4, 2.8, and 3.1 times faster than those in the presence of CuBi2O4, InVO4, and BiVO4, respectively. The enhanced photocatalytic performance could be partially attributed to the good light absorption of CuBi2O4, which broadens the visible light response of the InVO4/CuBi2O4/BiVO4 composites. Meanwhile, the interfacial chemical bonds in the dual Z-scheme heterojunction help accelerate charge separation and maintain strong redox activity. In addition, the oxygen vacancies, induced mainly by the low-valent vanadium atoms, facilitate the production of singlet oxygen (1O2) through energy transfer, which easily attacks the electron-rich groups, including phenolic group, dimethylamino group, amine group, and double bonds, in tetracycline. The InVO4/CuBi2O4/BiVO4 composite exhibited excellent reusability and stability, and performed well in photocatalytic degradation of tetracycline in river water and under natural sunlight, demonstrating great potential for practical application. The probable photocatalytic mechanism of InVO4/CuBi2O4/BiVO4 composite was proposed according to the results of density functional theory (DFT) calculations, and the reactive oxygen species (ROSs) and major degradation intermediates detected in the photocatalytic system. This work demonstrates the important roles of oxygen vacancies and interfacial chemical bonds in boosting the photocatalytic activity of Z-scheme heterojunctions and provides a reference for the construction of high-activity photocatalysts for efficient degradation of antibiotics.

Simultaneous Inhibition of Zn Dendrites and Polyiodide Ions Shuttle Effect by an Anion Concentrated Electrolyte Membrane for Long Lifespan Aqueous Zinc-Iodine Batteries.

Aqueous zinc-iodine (Zn-I2) batteries have attracted extensive attention due to their merits of inherent safety, wide natural abundance, and low cost. However, their application is seriously hindered by the irreversible capacity loss resulting from both anode and cathode. Herein, an anion concentrated electrolyte (ACE) membrane is designed to manipulate the Zn2+ ion flux on the zinc anode side and restrain the shuttle effect of polyiodide ions on the I2 cathode side simultaneously to realize long-lifetime separator-free Zn-I2 batteries. The ACE membrane with abundant sulfonic acid groups possesses a multifunctional amalgamation of good mechanical strength, guided Zn2+ ion transport, and effective charge repulsion of polyiodide ions. Moreover, rich ether oxygen, carbonyl, and S-O bonds in anionic polymer chains will form hydrogen bonds with water to reduce the proportion of free water in the ACE membrane, inhibiting the water-induced interfacial side reactions of the Zn metal anode. Besides, DFT calculations and in-situ UV-vis and in situ Raman results reveal that the shuttle effect of polyiodide ions is also significantly suppressed. Therefore, the ACE membrane enables a long lifespan of Zn anodes (3700 h) and excellent cycling stability of Zn-I2 batteries (10000 cycles), thus establishing a substantial base for their practical applications.

Understanding of the synergy effect of DBD plasma discharge combined to photocatalysis in the case of Ethylbenzene removal: Interaction between plasma reactive species and catalyst

Hybrid non-thermal plasma combined with photocatalysis is an efficient technology for the degradation of volatile organic compounds (VOCs) and leads to a synergetic boosting effect of the degradation process. Herein, the degradation of ethylbenzene (EB) in a hybrid lab-scale reactor was performed. In the combined mode (plasma DBD and photocatalysis [TiO2 + UVA]), the degradation of EB was synergetically boosted, and a higher degradation efficiency was reached. In this study, the behavior of the synergetic effect was investigated whilst varying several operational conditions, including the UV light source (UVA and UVC), the TiO2 weight (7.5–22.51 g·m-²), the addition of metallic dopants to the TiO2 at different weight ratios (x%Cu-TiO2 and x%MnO2-TiO2, where x = 1, 3, 5 and 10 for the weight ratios of Cu:TiO2 and MnO2:TiO2) and the catalyst support (glass fiber tissue [GFT] and nickel foam [NF] with different thicknesses [0.3–3.3 mm]). Moreover, the oxygen content (0–100%) in the reactor atmosphere was examined. The results showed an enhancement of the synergetic effect under UVC (TiO2 + UVC + DBD), which may be a consequence of intensive ozone decomposition under UVC and the generation of reactive atomic oxygen. The improvement of the synergetic effect under 1% Cu-TiO2 and 10% MnO2-TiO2 catalysts is assumed to reflect the role of metallic species in the production of oxygen species on the TiO2 surface via the ozone depletion mechanism. Furthermore, TiO2/NF (3.3 mm) showed the highest synergetic effect, likely due to the conductive character and the 3D porous structure of NF. Finally, the rich oxygen composition had an apparent impact on the synergetic effect.

Co-construction of oxygen doping and van der walls heterojunction in O-CB/ZnIn2S4 promoting photocatalytic production and activation of H2O2 for the degradation of antibiotics

The in situ production of H2O2 by photocatalysis have shown a sustainable strategy for water remediation, but the peroxide evolution capacity are still unsatisfactory. Herein, we ingeniously design oxygen-doped carbon black/zinc indium sulfide (O-CB/ZnIn2S4) composites for photocatalytic production and activation of H2O2 to degrade antibiotics. The rich oxygen dopants and van der walls heterojunction between O-CB and ZnIn2S4 promoted charge transfer, oxygen adsorption and reduction for peroxide generation. The optimized O-CB/ZnIn2S4-2 composites exhibited ultrahigh H2O2 production rate (1985 μmol/g/h) in pure water (pH=7) without sacrificial reagents and aeration assistance, which was 2 times, 3 times, and 12 times higher than CB/ZnIn2S4-2, ZnIn2S4 and O-CB, respectively. Additionally, O-CB/ZnIn2S4-2 composites exhibited considerable amount of OH of 30 μmol/L in 60 min, which was originated from the reduction of innergenerate-H2O2 by photogenerated electrons and direct photolysis. The degradation and quenching experiments shows that the innergenerate-H2O2 contributed to the rapid degradation and deep mineralization of tetracycline antibiotics(tetracycline, oxytetracycline, chlortetracycline hydrochloride). Moreover, intermediates analysis and toxicity estimation further confirm the significant mineralization and toxicity decrease during the degradation of oxytetracycline by O-CB/ZnIn2S4-2. The work provides deep insights into the crucial role of dopants and heterojunction in promoting H2O2 production and activation.

Design of ultrathin CoAl-LDHs/ZnIn2S4 with strong interfacial bonding and rich oxygen vacancies for highly efficient hydrogen evolution activity

Designing a semiconductor-based heterostructure photocatalyst is very important way to enhance the hydrogen production activity. Here, a novel 2D/2D CoAl-LDHs/ZnIn2S4 S-scheme heterostructure with an ultrathin structure was synthesized by electrostatic attraction between CoAl-LDHs and ZnIn2S4 nanosheets. The presence of oxygen vacancies in the monolayer CoAl-LDHs nanosheet promotes the formation of Co-SX bonds, which serve as charge transfer channels at the interface of the CoAl-LDHs/ZnIn2S4 heterostructure. The ultrathin CoAl-LDHs/ZnIn2S4 exhibits broadened light absorption in the near-infrared range due to the occurrence of Co-SX chemical bonds. The CoAl-LDHs/ZnIn2S4 with a mass ratio of 1:2 demonstrated the highest photocatalytic hydrogen evolution activity (1563.64 μmol g−1 h−1) under the simulated sunlight, which is 4.6 and 9.7 times than that of the ZnIn2S4 and CoAl-LDHs/ZnIn2S4(bulk), respectively. The enhanced photocatalytic activity of ultrathin 2D/2D CoAl-LDHs/ZnIn2S4 should attributed to the shorter carriers path that benefit from the ultrathin structure and the quicker photogenerated charge transfer and the S-scheme migration pathway accelerated by the charge channel of Co-SX bonds. These new ideas should be inspiring for the design and construction of heterostructures for higher photocatalytic hydrogen evolution activity.

Temperature-dependent NO2/diisopropylamine sensor based on SnO2 squama-wrapped tubes derived from waste bamboo shoot skin

The development of a conductometric sensor with dual-selectivity remains challenging because most sensors were only reported for sensing a given harmful gas. Accordingly, waste bamboo shoot skin (BSS) was selected as biotemplate and simply immersed in SnCl4 aqueous solution. Then, the obtained BSS precursor was calcined at 600 °C to reproduce biomorphic SnO2-6 squama-wrapped tubes, which achieved temperature-controlled dual-selectivity for two different gases. At a low temperature of 92 °C, SnO2-6 sensor has a super-high response (S = 1300) towards 10 ppm NO2, being obviously larger than most reported metal oxide-based sensors. Also it exhibits a good response (S = 46) towards 100 ppm diisopropylamine (DIPA) at 170 °C for the first time. Such excellent dual-sensing capability mainly relates to the synergism of uniform mesopore distribution, relatively large specific surface area and rich oxygen vacancy defects involved in SnO2-6 squama-wrapped tubes, which not only helps to accelerate rapid gas transport, but also efficiently exposes more active sites, increases the contents of adsorbed oxygen species and promotes surface chemical reactions. Meanwhile, the sensor has reversible response-recovery characteristic, good stability and humidity resistance to both gases. In addition, the dual-functional sensing mechanism was also investigated.

A Novel Combined Technology of Rich Reactive Oxygen Species and Ultrasound for the Decapsulation of Waste Cu(InGa)Se2 Solar Cells

A Novel Combined Technology of Rich Reactive Oxygen Species and Ultrasound for the Decapsulation of Waste Cu(InGa)Se₂ Solar Cells

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

Oxidation of renewable polyol/sugar into formic acid using molecular O2 over heterogeneous catalysts is still challenging due to the insufficient activation of both O2 and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO2 catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO2, the tri-coordinated Mn in the defective MnO2 catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mnδ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O2, as well as C–C and C–H bonds. As a result, the defective MnO2 catalyst shows high catalytic activity (turnover frequency: 113.5 h−1) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance.

Surface Modification of a Lignin-Derived Carbon-Supported Co-Based Metal/Oxide Nanostructure for Alkaline Water Splitting.

Exploring low-cost and eco-friendly bifunctional electrocatalysts of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolytes is still highly desired, and is crucial for water electrolysis and sustainable hydrogen generation. In this work, we report a facile pyrolysis-oxidation strategy to convert by-product lignin into bifunctional OER/HER electrocatalysts (Co/Co3O4-NPC-400) composed of Co/Co3O4 anchored on N-doped carbon with a surface of rich oxygen vacancies and oxygen-containing groups. The co-pyrolysis of lignin and NH4Cl can achieve a N-doped carbon matrix with a hierarchical pore structure, while the air-annealing process can induce the formation of oxygen-containing groups and oxygen vacancies. Owing to its surface properties, hierarchical pore structure and multiple active components, the constructed Co/Co3O4-NPC-400 possesses bifunctional catalytic activity and superior stability for OER/HER, especially for unexpected OER activity with a high current density of about 320 mA∙cm-2 at a potential of 1.8 V (vs. RHE). Water electrolysis using Co/Co3O4-NPC-400 as both the anode and the cathode needs a cell voltage of 1.95 and 2.5 V to attain about 10 and 400 mA∙cm-2 in 1 M KOH. This work not only provides a general strategy for the preparation of carbon-supported electrocatalysts for water splitting, but also opens up a new avenue for the utilization of lignin.

La and S Co-Doping Induced the Synergism of Multiphase Nickel-Iron Nanosheets with Rich Oxygen Vacancies to Trigger Large-Current-Density Oxygen Evolution and Urea Oxidation Reactions.

The development of cost-effective electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is of great significance for hydrogen production. Herein, La and S co-doped multiphase electrocatalyst (LSFN-63) is fabricated by metal-corrosion process. FeOOH can reduce the formation energy of NiOOH, and enhance the stability of NiOOH as active sites for OER/UOR. The rich oxygen vacancies can increase the number of active sites, optimize the adsorption of intermediates, and improve electrical conductivity. Beyond, La and S co-doping can also regulate the electronic structure of FeOOH. As a result, LSFN-63 presents a low overpotential of 210/450mV at 100/1000mA cm-2 , small Tafel slope (32mV dec-1 ), and outstanding stability under 1000mA cm-2 @60h, and can also display excellent OER activity with 180mV at 250mA cm-2 and long-term catalytic durability at 250mA cm-2 @135h in 30wt% KOH under 60 °C. Moreover, LSFN-63 demonstrates remarkable UOR performance in 1m KOH + 0.5m urea, which just requires an ultra-small overpotential of 140mV at 100mAcm-2 , and maintain long-term durability over 120h. This work opens up a promising avenue for the development of high-efficiency electrocatalysts by a facile metal-corrosion strategy.