Highly enhanced and stable activity of defect-induced titania nanoparticles for solar light-driven CO2 reduction into CH4

Photocatalytic reduction of CO₂ to fuel offers an exciting opportunity for helping to solve current energy and global warming problems. Although a number of solar active catalysts have been reported, most of them suffer from low product yield, instability, and low quantum efficiency. Therefore, the design and fabrication of highly active photocatalysts remains an unmet challenge. In the current work we utilize hydrogen-doped, blue-colored reduced titania for photocatalytic conversion of CO₂ into methane (CH₄). The photocatalyst is obtained by exposure of TiO₂ to NaBH₄ at 350 °C for 0.5 h. Sensitized with Pt nanoparticles, the material promotes solar spectrum photoconversion of CO₂ to CH₄ with an apparent quantum yield of 12.40% and a time normalized CH₄ generation rate of 80.35 μmol g^?1 h^?1, which to the best of our knowledge is a record for photocatalytic-based CO₂ reduction. The material appears intrinsically stable, with no loss in sample performance over five 6 h cycles, with the sample heated in vacuum after each cycle.     

Photooxidation of NOx using scheelite-type ABO4 (A = Ca,Pb; B = W,Mo) phases as catalyts

The scheelite-type compounds have been investigated due to their interesting properties of photoluminescence and recently, they have been applied as photocatalysts in air and water purification trough the removal of different organic and inorganic pollutants. In this work, four scheelite-type ABO₄ (A = Ca, Pb; B = W, Mo) compounds were prepared by co-precipitation method and its capacity to act as photocatalyst was evaluated in the removal of NO_x gases using the oxidation of nitric oxide (NO) as model reaction. The photocatalytic activity of the samples decreased in the following order: CaMoO₄ > PbWO₄ > PbMoO₄ > CaWO₄, which was related with the electronic properties associated with each sample. When the photocatalyst with the highest photocatalytic activity (CaMoO₄) was activated under UV radiation, the selectivity for the formation of NO₃^? ions was 35%, revealing the ability of the photocatalyst to carry out a deep oxidation of NO until innocuous products. Based in the modification of the experimental conditions, the mechanism proposed for the photooxidation of NO to NO₃^? ions was mainly by the action of the ion superoxide (O₂^?) formed from the O₂ adsorbed on CaMoO₄ surface.     

High performance magnetically recoverable g-C3N4/Fe3O4/Ag/Ag2SO3 plasmonic photocatalyst for enhanced photocatalytic degradation of water pollutants

The g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ nanocomposites have been successfully fabricated by facile refluxing method. The as-obtained products were characterized by XRD, EDX, SEM, TEM, UV–vis DRS, FT–IR, TGA, PL, and VSM techniques. The results suggest that the Ag/Ag₂SO₃ nanoparticles have anchored on the surface of g-C₃N₄/Fe₃O₄ nanocomposite, showing strong absorption in the visible region. The evaluation of photocatalytic activity indicates that for the g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ (40%) nanocomposite, the degradation rate constant was 188 × 10^?4 min^?1 for rhodamine B, exceeding those of the g-C₃N₄ (16.0 × 10^?4 min^?1) and g-C₃N₄/Fe₃O₄ (20.2 × 10^?4 min^?1) by factors of 11.7 and 9.3, respectively. The results showed that the nanocomposite prepared by refluxing for 120 min has the superior photocatalytic activity and its activity decreased with rising the calcination temperature. The trapping experiments confirmed that superoxide ion radical was the main active species in the photocatalytic degradation process. Also, it was demonstrated that the magnetic photocatalyst has considerable activity in degradation of one more dye pollutant. Finally, the reusability of the photocatalyst was evaluated by five consecutive catalytic runs. This work may open up new insights into the utilization of magnetically separable nanocomposites and provide new opportunities for facile fabrication of g-C₃N₄-based plasmonic photocatalysts.     

CeO2-Cu2O composite nanofibers: Synthesis,characterization photocatalytic and electrochemical application

The present study describes fabrication and electrochemical classification of one-dimensional CeO₂-Cu₂O nanofibers for photocatalysis and supercapacitor application. The utilized CeO₂-Cu₂O composite was prepared by sol–gel electrospinning method using Polyvinylpyrrolidone (PVP), Ce(NO₃)₃?6H₂O and Cu(CH₃COO)₂ as precursors. The physicochemical properties of the synthesized samples were characterized using special characterization approaches such as X-ray diffractometer (XRD), energy dispersive X-ray analysis (EDX), electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). As compared to pristine CeO₂, the UV–vis spectrum of CeO₂-Cu₂O composite exhibited the absorption peak which shifted to higher wavelength. The photocatalytic activity results indicated the substantial degradation of MB dye by ～92% over the surface of CeO₂-Cu₂O nanocomposite catalyst under visible light illumination. The CeO₂-Cu₂O composite possessed higher photocatalytic activity and electrochemical capacitance than the pristine samples as supercapacitor electrode materials. The CeO₂-Cu₂O composite exhibits a specific capacitance of 329.64 F g^?1 at 5 mV s^?1, which is higher than that of the pristine CeO₂ (192.5 F g^?1) nanofibers. These results suggest the applicability of fabricated composite nanofibers as visible light active photocatalyst and as electrode material for supercapacitors.     

Sol-gel synthesis,structural and enhanced photocatalytic performance of Al doped ZnO nanoparticles

In this research ZnO and Zn_1?x Al_xO (x = 1, 3, 5, 7% mol) nanoparticles were synthesized by sol-gel method. The effect of Al concentration on the structure, morphology, absorption spectra and photocatalytic properties investigated by using X-ray, TEM, EDS and UV–Vis spectrophotometer approaches. Hexagonal, spherical and rod-like structure was achieved as the dominant structure for undoped nanoparticles, low and high concentrations of doped Al, respectively. Photocatalytic activity of nanoparticles was measured by degradation of methyl orange as a pollutant under radiation of ultraviolet (UV). The experimental test results indicate that the best photocatalytic performance is at of 5% of Al. Furthermore, the doped ZnO nanoparticles have more activity in visible area compared with undoped nanoparticles. The absorption amount in this area increases by raising the Al concentrations. Furthermore, the band gap of the particles decreases from 3.22 eV to 2.93 eV by increasing Al percentage.     

Effect of trace HA on microstructure,mechanical properties and corrosion behavior of Mg-2Zn-0.5Sr alloy

Effect of the addition of trace HA particles into Mg-2Zn-0.5Sr on microstructure, mechanical properties, and bio-corrosion behavior was investigated in comparison with pure Mg. Microstructures of the Mg-2Zn-0.5Sr-xHA composites(x = 0, 0.1 and 0.3 wt%) were characterized by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy dispersion spectroscopy(EDS) and X-ray diffraction(XRD). Results of tensile tests at room temperature show that yield strength(YS) of Mg-2Zn-0.5Sr/HA composites increases significantly, but the ultimate tensile strength(UTS) and elongation decrease with the addition of HA particles from 0 up to 0.3 wt%. Bio-corrosion behavior was investigated by immersion tests and electrochemical tests. Electrochemical tests show that corrosion potential(Ecorr)of Mg-2Zn-0.5Sr/HA composites significantly shifts toward nobler direction from-1724 to-1660 m VSCE and the corrosion current density decreases from 479.8 to 280.8 μA cm~(-2) with the addition of HA particles. Immersion tests show that average corrosion rate of Mg-2Zn-0.5Sr/HA composites decreases from11.7 to 9.1 mm/year with the addition of HA particles from 0 wt% up to 0.3 wt%. Both microstructure and mechanical properties can be attributed to grain refinement and mechanical bonding of HA particles with second phases and α-Mg matrix. Bio-corrosion behavior can be attributed to grain refinement and the formation of a stable and dense CaHPO_4 protective film due to the adsorption of Ca~(2+)on HA particles. Our analysis shows that the Mg-2Zn-0.5Sr/0.3HA with good strength and corrosion resistance can be a good material candidate for biomedical applications.     

Effects of electrochemical synthetic conditions on surface property and photocatalytic performance of copper and iron-mixed p-type oxide electrodes

Earth-abundant copper and iron-mixed oxide(CuO/CuFeO_2; CFO) film electrodes are synthesized using an electrochemical deposition(ED) technique at two different ED potentials(-0.36 and-0.66 V vs saturated calomel electrode(SCE); denoted as ED-1 and ED-2, respectively). Then, their surface morphologies are compared, and the photo(electro)catalytic activities for the reduction of Cr(VI) are examined in aqueous solutions at pH 7 under simulated sunlight(AM 1.5 G; 100 mW cm~(-2)). The degree of the electrical potential applied to the ED process significantly affects the thickness of the synthesized electrode film and the intensity ratio of the diffraction peaks of CuO(111) and CuFeO_2(012). A 200 μm thick ED-2 sample with a distinct stacking of CuO on CuFeO_2 exhibits a larger broadband absorption spectrum than the 50-μm thick ED-1 with less separate stacking. Furthermore, the ED-2 sample has a higher intensity ratio of the diffraction peaks of CuO(111) and CuFe02(012) than ED-1. As-synthesized ED-2 samples produce larger photocurrents, leading to faster Cr(VI) reduction on the surface under given potential bias(-0.5 V vs SCE)or bias-free conditions. The energy levels(i.e., flatband potential) for the two samples are almost the same(only 10 mV difference), presumably supposing that the enhanced photoactivity of the ED-2 sample for Cr(VI) reduction is due to the facilitated charge transfer. The time-resolved photoluminescence emission spectra analysis reveal that the lifetime(r) of the charge carriers in the ED-1 sample is 0.103 ns, which decreases to 0.0876 ns in the ED-2. The ED-2 sample synthesized at a high negative potential is expected to contribute greatly to the application of other solar-to-fuel energy conversion fields as a highly efficient electrode material.     

Magnetic separation and adsorptive performance for methylene blue of mesoporous NiFe2O4/SBA-15 nanocomposites

Magnetic NiFe₂O₄/SBA-15 nanocomposites were synthesized by a facile impregnation method, and NiFe₂O₄ nanoparticles presented spinel phase structure and existed in the mesopores of SBA-15. Partial mesopores were blocked by NiFe₂O₄ nanoparticles and micropores formed, which the capillarity of micropores played a decisive role for methylene blue (MB) adsorption. The saturation magnetization increased from 2.34 emu g^?1 to 10.03 emu g^?1 with the NiFe₂O₄ content, while the specific surface area decreased from 552.18 m² g^?1 to 260.40 m² g^?1 and pore volume decreased from 1.13 cm³ g^?1 to 0.49 cm³ g^?1. MB adsorption could be improved by optimizing the NiFe₂O₄ content of the nanocomposites. MB could be adsorbed completely in 60 min with the optimum nanocomposites and could be separated easily from water by magnetic separation technique.     

Stable controlled growth of 3D CuO/Cu nanoflowers by surfactant-free method for non-enzymatic hydrogen peroxide detection

Sensitive, convenient and rapid detection of hydrogen peroxide(H_2 O_2) is highly desirable in fields like fundamental biological research, food industries, and clinical environmental analysis. Herein, a hierarchical porous CuO/Cu flower-like active electrode material for non-enzymatic H_2 O_2 sensor was synthesized via a low-cost and one-step chemical oxidation of Cu powder in water bath without surfactants. In order to discuss the growth mechanism of the product, products with different growth time length were fabricated. The electro-catalysis of all products were first exhibited by cyclic-voltammetry,and the product under 6 h reaction shows the best result. The detailed electro-catalytic behaviors of the best product(under 6 h reaction) are characterized by cyclic-voltammetry and amperometry under alkaline conditions. The materials have high sensitivity of 103 μA mM~(-1) cm~(-2)(R~2= 0.9979), low detection limit of 2 μmol/L and wide concentration range(from 2 μmol/L to 19.4 mmol/L). Large specific surface area and stabled nanostructure enabled good features, such as stability and sensitivity for the H_2 O_2 determination.     

Highly dispersible and uniform size Cu2ZnSnS4 nanoparticles for photocatalytic application

Highly dispersible, uniform size (～7 nm) single-phase Cu₂ZnSnS₄ nanoparticles have been synthesized by hydrothermal method using non-toxic surfactant (oleic acid). High resolution transmission electron microscopy image indicates good crystallinity of the Cu₂ZnSnS₄ nanoparticles with the growth along (1 1 2) plane. X-ray photoelectron spectroscopy analyses suggested that the formation of with Cu, Zn, and Sn in +1, +2 and +4 oxidation states. The optical absorption spectrum of Cu₂ZnSnS₄ nanoparticles exhibits an absorption in the visible region and its optical band gap was found to be ～1.72 eV, which could be much more appropriate for photocatalytic application under visible light irradiation. These Cu₂ZnSnS₄ nanoparticles have been shown high photocatalytic degradation activity of methylene blue (MB) dye in the presence of visible light irradiation. The rate constant (k) value of Cu₂ZnSnS₄ nanoparticles is found to be 0.0144 min^?1. We have discussed the mechanism of dye degradation process that drives the photocatalytic degradation process. The reusability of the Cu₂ZnSnS₄ nanoparticles for the dye degradation is also demonstrated.     

Synthesis of porous carbon spheres derived from lignin through a facile method for high performance supercapacitors

Porous carbon spheres (PCS) derived from lignin have been prepared through a facile method and fabricated as electrodes for electric double-layer capacitors. Spherical shaped mixtures of lignosulfonate and crystalized KOH are formed by spray drying of a solution of lignosulfonate and KOH. Activation by KOH is performed at high temperatures along with lignosulfonate carbonization. With an appropriate pore structure, the obtained PCS have a specific surface area of 1372.87 m² g^?1 and show a capacitance of 340 F g^?1 in 3 M KOH at a current density of 0.5 A g^?1. Moreover, a symmetric supercapacitor fabricated using the PCS as electrodes show a maximum capacitance of 68.5 F g^?1, and an energy density of 9.7 W h kg^?1 at a power density of 250 W kg^?1. The capacity retention is more than 94.5% after 5000 galvanostatic charge-discharge cycles. The excellent characteristics seem to be ascribed to the pore structures of PCS that have a large specific surface area and a low electrical resistance.     

Fabrication of Ag-doped MoO3 and its nanohybrid with a two-dimensional carbonaceous material to enhance photocatalytic activity

Recently, two-dimensional (2D) carbon-based materials and their nanocomposites have gained considerable fascination as a photocatalysts due to their remarkable contribution towards photocatalytic water splitting and remediation. Herein, a novel 2D reduced graphene oxide (rGO) based silver doped molybdenum trioxide (Ag/MoO₃) photocatalyst was synthesized successfully via hydrothermal and ultra-sonication methods. The surface structure, morphology, functional group characterization, and bandgap of the synthesized photocatalysts were analyzed using advanced physicochemical techniques. The photocatalytic performance of the prepared materials was scrutinized for Methylene blue (MB) dye degradation under solar light illumination. Because of its lower charge transfer resistance (19.54 Ω) and higher electrical conductivity (12.74 × 10² Sm^?1) the rGO/Ag/MoO₃ photocatalyst demonstrated significantly higher photocatalytic activity for dye removal than pure MoO₃ and Ag/MoO₃ photocatalysts. In particular, the rGO/Ag/MoO₃ photocatalyst illustrated about 98% dye degradation at a rate constant (0.0571 min^?1) greater than MoO₃ (0.0097 min^?1) and Ag/MoO₃ (0.0184 min^?1). Ag doping and the addition of rGO sheets led to enhanced optical absorbance and effectual separation of photo-induced electron-hole pairs, causing major progress in the photocatalytic behavior of MoO₃. Transient photocurrent results revealed longstanding photo-excited charge carriers in the graphene-based material.     

Co2(OH)3Cl nanoparticles as new-type electrode material with high electrochemical performance for application in supercapacitor

In this work, we report the preparation of Co₂(OH)₃Cl nanoparticles with average size of ～20 nm and well-defined cubic shape at room temperature by an epoxide precipitation route. It was found that the as-prepared Co₂(OH)₃Cl nanoparticles could be used as a promising new electrode material for application in redox supercapacitors due to its high electrochemical performance. It presented superior specific capacitance of 783 F g^?1 at low current density of 2.8 A g^?1, while it had a high value of 604 F g^?1 at high current density of 56.6 A g^?1, proving its excellent high rate performance. Its 75% capacitance retention after 10,000 cycles of charge–discharge demonstrated its long-life span. According to characterization results, the possible mechanism for the electrochemical process that Co₂(OH)₃Cl nanoparticles underwent was proposed as a process of Co₂(OH)₃Cl → β-Co(OH)₂ → CoOOH ? Co₃O₄.     

A study on preparation and photocatalytic characterization of conjugated polymer/ZnS complex

A conjugated polymer/ZnS complex was successfully synthesized and characterized by the methods of FTIR, UV–vis, ESR and TEM. The result showed that the conjugated polymer/ZnS complex could extend the absorption band to the visible region (190–700 nm), whereas pure ZnS could be activated under ultraviolet light (<380 nm) irradiation only. Photocatalytic experiment showed that the conjugated polymer/ZnS complex had extremely high photocatalytic activity for degradation of dyes. The conjugated polymer played an important role in the photocatalytic degradation of dyes.     

High efficiency visible-light-driven Fe2O3-xSx/S-doped g-C3N4 heterojunction photocatalysts: Direct Z-scheme mechanism

Several nanoporous Fe_2 O_3-xSx/S-doped g-C_3 N_4(CNS) Z-scheme hybrid heterojuctions have been successfully synthesized by one-pot in situ growth of the Fe_2O_3-xSx particles on the surface of CNS. The characterization results show that S-doping in the g-C3 N4 backbone can greatly enhance the charge mobility and visible light harvesting capability. In addition, porous morphology of hybrid composite provides available open pores for guest molecules and also improves light absorbing property due to existence of multiple scattering effects. More importantly, the Fe_2 O_3-xSx nanoparticles formed intimate heterojunction with CNS and developed the efficient charge transfer by extending interfacial interactions occurred at the interfaces of both components. It has been found that the Fe_2 O_3-xSx/CNS composites have an enhanced photocatalytic activity under visible light irradiation compared with isolated Fe_2 O_3 and CNS components toward the photocatalytic degradation of methylene blue(MB). The optimal loaded Fe_2 O_3-xSx value obtained is equal to 6.6 wt% that provided 82% MB photodegradation after 150 min with a reaction rate constant of 0.0092 min~(-1) which was faster than those of the pure Fe_2 O_3(0.0016 min~(-1))and CNS(0.0044 min~(-1)) under the optimized operating variables acquired by the response surface methodology. The specific surface area and the pore volume of Fe_2 O_3(6.6)/CNS hybrid are 33.5 m~2/g and0.195 cm~3/g, which are nearly 3.8 and 7.5 times greater compared with those of the CNS, respectively. The TEM image of Fe_2 O_3(6.6)/CNS nanocomposite exhibits a nanoporous morphology with abundant uniform pore sizes of around 25 nm. Using the Mott-Schottky plot, the conduction and valence bands of the CNS are measured(at pH = 7) equal to-1.07 and 1.48 V versus normal hydrogen electrode(NHE), respectively.Trapping tests prove that ·OH-and ·O_2-radicals are major active species in the photocatalytic reaction.It has been established that formation of the Z-scheme Fe_2 O_3(6.6)/CNS heterojunction between CNS and Fe_2 O_3 directly produces ·OH as well as ·O_2-radicals which is consistent with the results obtained from trapping experiments.     

Impact of Pt loading methods over mesoporous-assembled TiO2–ZrO2 mixed oxide nanocrystal on photocatalytic dye-sensitized H2 production activity

In this work, the photocatalytic water splitting under visible light irradiation for hydrogen production was investigated by using Eosin Y-sensitized Pt-loaded mesoporous-assembled TiO₂–ZrO₂ mixed oxide nanocrystal photocatalysts. The mesoporous-assembled TiO₂–ZrO₂ mixed oxide with the TiO₂-to-ZrO₂ molar ratio of 95:5 (i.e. 0.95TiO₂–0.05ZrO₂) was synthesized by using a sol–gel process with the aid of a structure-directing surfactant. The Pt loading was comparatively performed via two different effective methods: single-step sol–gel (SSSG) and photochemical deposition (PCD). The synthesized photocatalysts were methodically characterized by N₂ adsorption–desorption, XRD, UV–visible spectroscopy, SEM–EDX, TEM–EDX, TPR, and H₂ chemisorption analyses. The results revealed that the Pt loading by the PCD method greatly enhanced the photocatalytic hydrogen production activity of the synthesized mesoporous-assembled 0.95TiO₂–0.05ZrO₂ mixed oxide photocatalyst more than that by the SSSG method. The optimum Pt loading by the PCD method was experimentally observed at 0.5 wt.%, which was well associated with the maximum Pt dispersion. In addition, the PCD conditions, i.e. UV light irradiation time and UV light intensity, were investigated and optimized to be 2 h and 44 W, respectively.     

Influence of ZnO concentration on the optical and photocatalytic properties of Ni-doped ZnS/ZnO nanocomposite

Photocatalysts consisting of nickel-doped ZnS/ZnO core shell nanocomposites with varying concentrations of ZnO was synthesized through chemical precipitation method. The catalyst was deployed in photocatalytic degradation of indigo carmine dye as a model organic pollutant. Characterization of the samples was achieved through the use of X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, UV–vis spectroscopy and energy dispersive spectroscopy. The composites consist of wurtzite ZnO phase deposited on cubic ZnS. Optical absorption, crystallite sizes and photocatalytic degradation efficiency increased with increasing ZnO concentration. Bandgap values of ZnS also decreased appreciably with increase in ZnO concentration. Ni-doped ZnS/(0.5 M ZnO) was identified as the most efficient catalyst with 91% dye degradation efficiency at a rate of 15.38 × 10^?3 min^?1 in 180 min. Meanwhile, the pristine ZnS degraded 25% of the dye at the rate of 1.53 × 10^?3 min^?1 within the same time. The Ni-doped Zns/(0.5 M ZnO) was used to degrade the dye on the basis of influence of factors such as solution temperature, hydrogen peroxide (H₂O₂) and ethanol contents. Dye degradation increased with increase in temperature, but decreased with ethanol content. H₂O₂ content initially caused enhanced dye degradation but the efficiency decreased with higher H₂O₂ content.     

Synthesis and photocatalytic activity of mesoporous cerium doped TiO2 as visible light sensitive photocatalyst

Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N₂ adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 °C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 °C shows better activity than that calcined at 400 °C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce⁴⁺/Ce³⁺ rather than only visible light absorption.     

Synthesis and characterization of novel magnetically separable NiFe2O4@AlMCM-41-Cu2O core-shell and its performance in removal of dye

The synthesis of magnetic NiFe₂O₄@AlMCM-41-Cu₂O core-shell as a new class of visible light driven photocatalyst was suggested. The magnetic NiFe₂O₄ core was prepared by solvothermal method. The intermediate AlMCM-41 shell was prepared by the method of liquid crystal templating mechanism and subsequently cuprous oxide (Cu₂O) nanoparticles (NPs) were synthesized in NiFe₂O₄@AlMCM-41core-shell via colloidal chemistry approach. The properties of prepared magnetic core-shell were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption–desorption measurement and vibration sample magnetometer (VSM). Based on EDX results, the weight percentage (wt%) of NiFe₂O₄ core, MCM-41 shell and Cu₂O NPs were calculated to be 68.89, 30.55 and 0.56%, respectively. It consisted of mesoporous structure with a surface area of 687.00 m² g^?1, an average pore size of 2.95 nm and possessed excellent magnetic properties of 4.74 emu g^?1. The TEM results indicated that the NiFe₂O₄ as core were regular spheres with diameter of 68 nm, and the average thickness of AlMCM-41 shells was ～35 nm. The particles size of Cu₂O incorporated in core-shell was less than 5 nm. The photocatalytic activity was evaluated under visible light irradiation using the removal of methylene blue (MB) dye as a model reaction. The removal rate of MB achieved up to 90% after 60 min under visible light irradiation, and the NiFe₂O₄@AlMCM-41-Cu₂O can be recycled and reused.     

Self-nitrogen-doped porous biochar derived from kapok (Ceiba insignis) fibers: Effect of pyrolysis temperature and high electrochemical performance

Self-nitrogen-doped porous biochar derived from kapok fibers possesses unique structure and excellent electrochemical performance. In this study, one-step pyrolysis method was introduced to prepare porous biochar from kapok fibers, and effect of pyrolysis temperature on structure and electrochemical performance of the porous biochar was investigated. It was found that pyrolysis temperature played an important role in determining microstructure of the biochar. At the pyrolysis temperature of 750 °C, the as-prepared biochar (C_KF-750) represented a largest specific surface area of 1125.7 m² g^?1 and pore volume of 0.7130 m³ g^?1, and hence brings C_KF-750 a highest specific capacitance of 283 F g^?1 at a current density of 1 A g^?1 in a 6 mol L^?1 KOH electrolyte. Furthermore, the cycle stability of C_KF-750 was wonderful, and the specific capacitance retained almost constant after 10000 cycles. Therefore, the pyrolysis temperature of 750 °C is optimal for the preparation of porous biochar as an outstanding electrode material for supercapacitor.