A novel carbon aerogel prepared for adsorption of copper(II) ion in water

A novel carbon aerogel with network pore and surface group of hydroxyl was prepared from cellulose colloid, through sol-gel reaction, freeze-drying and carbonization. Surfactant like isooctyl alcohol ether phosphate was taken as structure inducer in sol-gel reaction, for construction of porous network in the prepared samples. Characteristic of a specific area about 725.12 m²/g and total pore volume about 0.64 cm³/g, the prepared cellulose-based carbon aerogel of CCA₂, has a maximum capacity about 55.25 mg/g for Cu²⁺ in neutral aqueous solution. Its adsorption equilibrium can be reached within 10 min in an aqueous solution of pH7.0 at 25?°C, while desorption of Cu²⁺ need about 1 h eluted by HCl or HNO₃ solution of 0.01 M. And regeneration of the carbon aerogel in adsorption of Cu²⁺ can be repeated for five times, remaining 96% adsorption capacity. It is also found in adsorption process the kinetics nicely follows pseudo-second-order rate expression, and the isotherm fits Langmuir model.     

Facile synthesis of Cu<Subscript>x</Subscript>O (x = 1, 2)/TiO<Subscript>2</Subscript> nanotube arrays as an efficient visible-light driven photocatalysts

TiO₂ nanotube arrays (TNTs) modified with Cu_xO (x = 1, 2) were prepared by a simple impregnation-calcinations method. The obtained samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy , UV–Vis diffuse reflectance spectroscopy and photocurrent tests. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. Compared with pure TNTs, the Cu_xO/TNTs composite exhibited much higher photocatalytic activity under visible-light irradiation (λ > 420 nm). The photocatalytic activity of the composite was related to impregnation time of the copper nitrate solution, and an optimal time was 2 h. The activity of 2-Cu_xO/TNTs displayed 4.9 times as high as that of pure TNTs. The enhanced photocatalytic performance is mainly attributed to the synergistic effects of initiating visible-light absorption and the matched band edge positions of Cu₂O, CuO and TiO₂. Also, a possible mechanism on the Cu_xO/TNTs photocatalytic degradation of RhB is proposed. Overall, the inexpensive and environmentally friendly photocatalyst, as promising materials, could be used to remove some aquatic pollutants in the field of water purification.     

In-situ generation Cu2O/CuO core-shell heterostructure based on copper oxide nanowires with enhanced visible-light photocatalytic antibacterial activity

As visible light-driven photocatalysts in wastewater treatment, Cu₂O/CuO composites have garnered considerable attention. Herein, Cu₂O/CuO core–shell nanowires were fabricated directly on a Cu mesh using a simple two-step synthesis process involving a wet chemical method and rapid annealing. Unlike conventional composite nanowires, controllable core–shell nanowires exhibit high photoelectrochemical properties and overcome the problems associated with the recovery of powder-based photocatalysts. The presence and structural distribution of the Cu₂O/CuO core–shell nanowires were confirmed using X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Among the samples subjected to different rapid annealing temperatures for 180 s, the sample exposed to rapid annealing at 350 °C achieved the highest photocurrent density of ?6.96 mA cm^?2. In the core–shell nanowires fabricated on the samples, the ratio of Cu₂O/CuO was 1:1. The photocatalytic activity of the Cu₂O/CuO nanowire samples was also determined by measuring methyl blue degradation to determine their applicability in wastewater treatment. A remarkable photocatalytic degradation rate of 91.6% was achieved at a loading bias voltage of ?0.5 V. The Cu₂O/CuO heterojunction enhanced the photodegradation of the samples because the different bandgaps improved the dissociation of the photogenerated electron–hole pairs. Furthermore, the antibacterial activity of the Cu₂O/CuO nanowires exhibited considerable resistance against Escherichia coli and photocatalytic antibacterial treatment for only 20 min under visible light killed 10⁶ CFU/mL of E. coli. Therefore, the Cu₂O/CuO controllable core–shell nanowires with a high photodegradation performance and excellent antibacterial activity under general illumination show diverse applications in water treatment.     

Preparation of Cu2O/TiO2 composite porous carbon microspheres as efficient visible light-responsive photocatalysts

In this paper, Cu₂O/TiO₂ composite porous microspheres were prepared in the absence of templates and additives by a simple hydrothermal method using Cu(CH₃COO)₂·H₂O and (NH₄)₂TiF₆ as precursors. The photocatalytic activity of the samples was evaluated by the photo-degradation of methylene blue (MB) aqueous solution under the visible-light illumination. To the best of our knowledge, this is the first report on the preparation and photocatalytic activity of Cu₂O/TiO₂ composite porous microspheres with a template-free hydrothermal method. This work may provide new insights into preparing other inorganic porous microspheres.     

A unique Cu2O/TiO2 nanocomposite with enhanced photocatalytic performance under visible light irradiation

A unique Cu₂O/TiO₂ nanocomposite with high photocatalytic activity was synthesized via a two-step chemical solution method and used for the photocatalytic degradation of organic dye. The structure, morphology, composition, optical and photocatalytic properties of the as-prepared samples were investigated in detail. The results suggested that the Cu₂O/TiO₂ nanocomposite is composed of hierarchical TiO₂ hollow microstructure coated by a great many Cu₂O nanoparticles. The photocatalytic performance of Cu₂O/TiO₂ nanocomposite was evaluated by the photodegradation of methylene blue (MB) under visible light, and compared with those of the pure TiO₂ and Cu₂O photocatalysts synthesized by the identical synthetic route. Within 120 min of reaction time, nearly 100% decolorization efficiency of MB was achieved by Cu₂O/TiO₂ photocatalyst, which is much higher than that of pure TiO₂ (26%) or Cu₂O (32%). The outstanding photocatalytic efficiency was mainly ascribed to the unique architecture, the extended photoresponse range and efficient separation of the electron-hole pairs in the Cu₂O/TiO₂ heterojunction. In addition, the Cu₂O/TiO₂ nanocomposite also retains good cycling stability in the photodegradation of MB.     

Thermal conversion synthesis of Cu2O photocathode and the promoting effects of carbon coating

Simplifying the synthesis of cuprous oxide (Cu₂O) photocathode has turned out to be critical for scalable application. Herein, we present a novel thermal conversion approach to synthesize a shell/core structured Cu₂O/Cu photocathode. In this method a shell comprising a mixture of CuO and Cu₂O is obtained by heating Cu mesh at 500 °C in air beforehand, and subsequent annealing in N₂ atmosphere converts the unwanted CuO into Cu₂O gradually, which results in the desired Cu₂O/Cu structure. A slightly viscous starch sol coats the Cu₂O shell as carbon source, after carbonizing under N₂ atmosphere, the Cu₂O/Cu is covered with compact carbon films, i.e. C/Cu₂O/Cu. Photoelectrochemical experiments reveal that the introduction of carbon layers on Cu₂O enhances the photocurrent density from − 1.5 to − 2.75 mA·cm^− 2 at 0 V vs. reversible hydrogen electrode (RHE). Moreover, the deposition of carbon films on Cu₂O in this work has little effect on improving the stability.     

Experimental Study on Photocatalytic Activity of Cu2O/Cu Nanocomposites Under Visible Light

Cu₂O/Cu nanocomposites (NCs) are synthesized using a two-step hydrothermal method, their different phase compositions are obtained by adjusting the reaction time, and then, they are used as photocatalysts to degrade dye Procion Red MX-5B (PR), methylene blue (MB) and methyl orange (MO) under visible-light. Experimental results indicate Cu₂O/Cu NCs exhibit a much higher photocatalytic activity than pure Cu₂O, they remain almost unchanged in their phase compositions in the long photocatalytic reaction process, except for partial oxidation of particle surface. They still exhibit a high photocatalytic activity even at the end of four photocatalytic reaction cycles. It can therefore be concluded that Cu₂O/Cu nanocomposites are good candidates for processing of pollutant water.     

In-situ synthesis and textural evolution of the novel carbonaceous SiC/mullite aerogel via polymer-derived ceramics route

A novel carbonaceous SiC/mullite composite aerogel is derived from catechol-formaldehyde/silica/alumina hybrid aerogel (CF/SiO₂/AlOOH) via polymer-derived ceramics route (PDCR). The effects of the reactants concentrations on the physicochemical properties of the carbonaceous SiO₂/Al₂O₃ aerogel and SiC/mullite aerogel are investigated. The mechanism of the textural and structural evolution for the novel carbonaceous SiC/mullite is further discussed based on the experimental results. Smaller reactants concentration is favorable to formation of mullite. Reactants concentration of 25% is selected as the optimal condition in considering of the mullite formation and bulk densities of the preceramic aerogels. Spherical large silica particles are also produced during heat treatment, and amorphous silica is remained after this reaction. With further heat treatment at 1400 °C, silicon carbide and mullite coexist in the aerogel matrix. The mullite addition decreases the temperature of SiC formation, when compared with the conventional methods. However, after heat treatment at 1450 °C, the amount of mullite begins to decrease due to the further reaction between carbon and mullite, forming more silicon carbide and alumina. The carbonaceous SiC/mullite can be transferred to SiC/mullite binary aerogel after carbon combustion under air atmosphere. The carbonaceous SiC/mullite has a composition of SiC (31%), mullite (19.1%), SiO₂ (14.4%), and carbon (35%). It also possesses a 6.531 nm average pore diameter, high surface area (69.61 m²/g), and BJH desorption pore volume (0.1744 cm³/g). The oxidation resistance of the carbonaceous SiC/mullite is improved for 85 °C when compared with the carbon based aerogel.     

Creating dual charge transfer channels to collaborative enhance the photocatalytic bacteriostatic efficiency and photocorrosion resistance of Cu2O based nanocomposites

Cuprous oxide (Cu₂O), as one of the traditional photocatalytic antifouling agents, has its own defects for practical applications such as rapid recombination of carriers, serious photocorrosion (Cu₂O changing into CuO) and explosive release of cuprous ions. Herein, a novel ternary interfacial heterojunction (Cu₂O/C/CCN) was prepared by carbon doping of g-C₃N₄ followed by in-situ carbon film covering and Cu₂O loading. Compared with pure Cu₂O and Cu₂O/g-C₃N₄, Cu₂O/C/CCN presented more powerful broad-spectrum and long-term photocatalytic antibacterial properties against S. aureus and P. aeruginosa, and the antibacterial rate remained at approximately 94.28% and 90.54%, respectively, even after storage 30 days. The high antibacterial rate of the Cu₂O/C/CCN can be attributed to the high photocatalytic performance and stable and continuous release of cuprous ions. The carbon doping of g-C₃N₄ could adjust its band gap and promote more efficient photoexcited carrier generation and transfer by the formation of delocalized large π bonds like “electron bridge” as the first charge transfer channel. The existence of carbon film between g-C₃N₄ and Cu₂O can build the second highly efficient charge transfer channel for the separation of photoexcited carriers by forming a Z-scheme interfacial heterojunction. DFT calculation and fluorescence spectrum results showed that more active electrons on CCN tend to transfer to Cu₂O through the two nonradiative decay pathways. The highly efficient carrier transport and separation can also greatly reduce the 15.3% generation of CuO compared to Cu₂O/g-C₃N₄. The more negative reduction potential further promoted the ROS generation for sterilization. In addition, the loading of Cu₂O on 2D C/CCN can reduce the contact area between Cu₂O and solution and then slow the release rate of cuprous ions by 75% compared to Cu₂O. Therefore, Cu₂O/C/CCN has great potential for practical antifouling applications.     

The compatibility of transition metal oxide/carbon composite anode and ionic liquid electrolyte for the lithium-ion battery

Three types of transition metal oxide/carbon composites including Fe₂O₃/C, NiO/C and CuO/Cu₂O/C synthesized via spray pyrolysis were used as anode for lithium ion battery application in conjunction with two types of ionic liquid: 1 M LiN(SO₂CF₃)₂ (LiTFSI) in 1-ethyl-3-methyl-imidazolium bis(fluorosulfonlyl)imide (EMI-FSI) or 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (Py13-FSI). From the electrochemical measurements, the composite electrodes using Py13-FSI as electrolyte show much better electrochemical performance than those using EMI-FSI as electrolyte in terms of reversibility. The Fe₂O₃/C composite shows the highest specific capacity and the best capacity retention (425 mAh g⁻¹) under a current density of 50 mA g⁻¹ for up to 50 cycles, as compared with the NiO/C and CuO/Cu₂O/C composites. The present research demonstrates that Py13-FSI could be used as an electrolyte for transition metal oxides in lithium-ion batteries.     

Cu2O/rGO复合材料修饰阴极强化MFC产电脱氮性能及其机理

微生物燃料电池(MFC)在处理含硝酸盐(NO_3^--N)废水时具有同时产电和脱氮的潜力,寻找成本低且改善其产电脱氮性能的阴极修饰材料是MFC在含氮废水处理领域应用的关键。氧化亚铜/还原氧化石墨烯(Cu₂O/rGO)复合材料具有良好的电化学性能,在替代铂基材料提高MFC性能方面具有一定的应用前景。本研究通过还原法制备了Cu₂O/rGO复合材料,并对材料的结构和氧还原性能进行表征；同时,将其负载于阴极碳布后分析其电化学性能,并通过MFC的输出电压、功率密度和NO_3^--N的去除率探究Cu₂O/rGO阴极对MFC产电和脱氮性能的强化作用；通过对反硝化相关酶活性和胞外聚合物的测定,探究Cu₂O/rGO阴极强化MFC性能的机理。结果表明：Cu₂O/rGO复合材料具有大量的介孔结构,能够为电子传递提供更多的通道,并且Cu₂O/rGO复合材料具有良好的氧化还原可逆性；与Pt/C阴极相比,Cu₂O/rGO阴极的交换电流密度升高33.53%,电子转移阻力降低65.53%；Cu₂O/rGO-MFC在处理NO_3^-N废水时获得的最大平均输出电压(662.54 mV)、最大功率密度(26.27 mW/cm^₂)、平均库伦效率(32.02%)和NO_3^--N去除速率(83.33 mg NO_3^--N L/h)均高于Pt/C-MFC(485.33 mV,16.98 mW/cm^₂,7.38%,41.67 mg NO_3^--N L/h)；Cu₂O/rGO复合材料通过提高MFC阴极反硝化关键酶活性和类蛋白组分含量,改善了MFC的产电和脱氮性能。     

Preparation and characterization of RuO<Subscript>2</Subscript> · <Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O/carbon aerogel composites for supercapacitors

A series of RuO₂ · xH₂O/carbon aerogel (CA) composite electrode materials was prepared by a chemical precipitation method. Ultrasonication was used to accelerate the chemical reaction and improve the dispersion of RuO₂ · xH₂O particles on the surface and the pores of the aerogel. The structure and morphology of the as-prepared composite were characterized by N₂ adsorption isotherm, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM). The results showed that the CA had a pearly network structure and the composites had a relatively high specific surface area and mesopore volume. The electrochemical performance of the composite electrodes was studied by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance measurements. The results indicated a substantial increase in the specific capacitance of the composite. Moreover, the utilization efficiency of RuO₂ · xH₂O was greatly improved by loading it on the conductive and porous CA due to a significant improvement in the inter-particle electronic conductivity and the extensive mesoporous network of the composites.     

Cu2O-based binary and ternary photocatalysts for the degradation of organic dyes under visible light

As competitive photocatalysts, Cu₂O nanoparticles meet with severe photogenerated carries recombination and insufficient light absorption, leading to the poor photocatalytic performance. Herein, the truncated Cu₂O-Au (CA) binary and Cu₂O-Au-TiO₂ (CAT) ternary octahedra with Au nanoparticles (Au NPs), preferentially supported on the (110) and (100) planes of Cu₂O, are synthesized for efficient photocatalytic degradation reactions. The photodegradation rates of MO of CA1 (Cu₂O-Au containing 1 wt % Au) and CAT are as high as 95.61% and 96.5% under 60 min of visible light irradiation, respectively. On the one hand, the synergistic function of localized surface plasmon resonance (LSPR) of Au NPs and Schottky barrier accelerate the separation and transfer of photogenerated carriers. On the other hand, a Z-scheme electron transfer system is constructed in CAT to promote the photodegradation performance. According to the finite-difference-time-domain (FDTD) simulation result, there is a strong electric field enhancement at the contact sites between Au, Cu₂O and TiO₂, which accelerates the electron transfer to a large extent and separates the electron-hole pairs. Therefore, this work may provide an approach for the synthesis and applications of multiple heterostructure catalyst.     

The effect of Cu addition on Ge-based composite anode for Li-ion batteries

A Ge/Cu₃Ge/C composite, prepared by pyrolysis and a high energy mechanical milling process, was investigated as an anode material for Li-ion batteries. Electron probe micro-analyzer images showed that Ge and Cu₃Ge were well dispersed in the carbon matrix. Various analytical techniques were carried out to clarify the reaction mechanism of the Cu₃Ge single phase and the Ge/Cu₃Ge/C composite ex situ XRD and ex situ HRTEM analyses for Ge/Cu₃Ge/C composite electrode were carried out and the final phase formed was Li₁₅Ge₄. For the case of pure Cu₃Ge electrode, it reacted with Li at very low rate and the final product was probably a Li-Ge compound. Electrochemical tests showed that the Ge/Cu₃Ge/C composite exhibited better capacity retention than that of the Ge/C composite anode probably due to the presence of amorphous carbon which acted as a buffering matrix during volume expansion and Cu that formed during the first discharge increased the electrical conductivity locally.     

Magnetic carbon aerogel pyrolysis from sodium carboxymethyl cellulose/sodium montmorillonite composite aerogel for removal of organic contamination

In this paper, we present a facile approach for the synthesis of polysaccharide-based carbon aerogel by sol–gel processing, freeze-drying, and pyrolysis of a sodium carboxymethyl cellulose/sodium montmorillonite composite aerogel. The as-prepared carbon aerogel was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, nitrogen adsorption measurements, and vibrating sample magnetometry. The carbon aerogel obtained in this study possessed low density (0.064?±?0.0029 g/cm³), a high surface area (185 m²/g), and flame retardance. Measurements of the magnetic properties indicated that the carbon aerogel exhibited typical ferromagnetic characteristic at room temperature. The absorption capacity of the carbon aerogel for oils and organic solvents is as much as 10–20 times its own weight. Moreover, a method of combustion could be employed to recycle the carbon aerogel. The results imply that the carbon aerogel is a potential cost-effective adsorbent for oil and organic pollutants from aqueous solutions in environmental pollution cleanup.     

Electrochemical properties of electrospun CuxO (x = 1, 2)-embedded carbon nanofiber with EXAFS analysis

The Cu_xO (x = 1, 2)-embedded carbon nanofibers (Cu_xO/CNF) were prepared by electrospinning of the composite solutions of Cu(II) acetate, PAN (polyacrylonitrile) and PVP (polyvinylpyrrolidone), and subsequent stabilization and carbonization. The structure of Cu₂O/CNF is largely dependent on the carbonization temperature. The Cu_xO/CNF-700 has the disordered CuO structure, while the Cu_xO/CNF-800 has the intermediate structure between the disordered CuO and Cu₂O. The structural change in the CNF prepared by electrospinning and optimum thermal treatment leads to excellent electrochemical properties. The CNF plays an important role as buffering agent to prevent Cu_xO particles from agglomerating. Besides, the aligned CNF with high electrical conductivity leads to the occurrence of Cu nano-particles in the discharging process, and it serves to convert Li₂O into Li in the charging process. Both Cu_xO/CNF-700 and Cu_xO/CNF-800 exhibit high specific discharge capacity, exceptional cycle retention, and excellent reversible capacity even in initial cycle, while Cu_xO/CNF-900 shows bad electrochemical performance.     

La-doped WO3@gCN Nanocomposite for Efficient degradation of cationic dyes

In present investigation, gCN supported carbon coated Lanthanum doped tungsten oxide (C@LWO/gCN) composite were synthesized via hydrothermal approach. The photodegradation of different cationic dyes like malachite green (MG), crystal violet (CV) and methylene blue (MB) has been carried out under prepared C@LWO/gCN composite. Furthermore, the comparative photodegradation was also performed using pristine LWO and C@LWO nanowires. The synthesized samples were characterized via physiochemical techniques such as XRD, FESEM, EDX, FTIR, BET and UV/Vis spectroscopy. The results proved incorporation of La ions into WO₃ lattice and reduced band gap of doped sample which significantly boost up the capability of the material towards photodegradation. The maximum degradation was found out at pH = 6, 5 mg catalyst dose, 5 ppm dye concentration and 35 °C temperature. The achieved results proved that the trapping agents compete with prepared composite specie for the h⁺, e⁻, HO^● and O₂^●- radicals. The obtained experimental records of photodegradation of cationic dyes using C@LWO/gCN composite has correlation with pseudo first order kinetics, Langmuir-Hinshelwood model and t_1/2. The simplest facile synthetic approach, remarkable photodegradation performance against colored and colorless effluents suggest that C@LWO/gCN composite exhibit great potential for large-scale wastewater treatment.     

Enhanced photodegradation activity of Rhodamine B by MgFe2O4/Ag3VO4 under visible light irradiation

MgFe₂O₄/Ag₃VO₄ composite photocatalysts were synthesized by a milling–calcining method. The results of Rhodamine B (RhB) photodegradation showed that the MgFe₂O₄/Ag₃VO₄ composite exhibited enhanced photodegradation activity under visible-light irradiation. The 0.2 wt.% MgFe₂O₄/Ag₃VO₄ calcined at 573 K exhibited the optimal photocatalytic behavior. Its maximum degradation rate was 5.4 times higher than that of Ag₃VO₄. Moreover, transient photocurrent-time was also investigated. Based on the results of the characterizations, the mechanism of enhanced photocatalytic activity is discussed.     

Enhanced photocatalytic performance through the ferroelectric synergistic effect of p-n heterojunction BiFeO3/TiO2 under visible-light irradiation

A BiFeO₃/TiO₂ p-n heterojunction photocatalyst with ferroelectric synergistic effect under visible-light irradiation was developed through facile hydrolysis and precipitation by forming nanospheres of TiO₂ on BiFeO₃ nanocube to improve the photocatalytic efficiency. Analyses of the microstructure, optical properties, and photoelectrochemical performance indicate the formation of a core–shell heterostructure of BiFeO₃/TiO₂ with excellent energy band matching. The BiFeO₃/TiO₂ p-n heterojunction has enlarged specific surface area, higher sensitivity to visible-light, and improved separation and transfer efficiency of photoelectron-hole pairs than single TiO₂ and BiFeO₃. Moreover, the composite exhibits superior photocatalytic degradation performance for methylene blue (MB) and common antibiotic tetracycline (TC) under UV and visible-light irradiation. The MB degradation rate within 180 min reaches 78.4% and 90.4% under UV and visible-light irradiation, respectively. Furthermore, the enhanced photocatalytic mechanism of BiFeO₃/TiO₂ is explored by photoluminescence (PL), electrochemical impedance spectroscopy (EIS), transient photocurrent analysis, radical quenching, and band structure characterization.     

Cu2O/TiO2 heterostructure nanotube arrays prepared by an electrodeposition method exhibiting enhanced photocatalytic activity for CO2 reduction to methanol

Cu₂O/TiO₂ composite nanotube arrays demonstrating enhanced photocatalytic performance were synthesized using an electrodeposition method to impregnate the p-type Cu₂O into the n-type titanium dioxide nanotube arrays (TNTs). The morphological results confirmed that the TNTs are wrapped by the Cu₂O nanoparticles and the UV–Vis absorption spectra showed that the Cu₂O/TNTs display a better ability for visible light absorption compared to the pure TNTs. CO₂ photocatalytic reduction experiments carried out by using Cu₂O/TNT nanocomposites proved that Cu₂O/TNTs exhibit high photocatalytic activity in conversion of CO₂ to methanol, while pure TNT arrays were almost inactive. Furthermore, Cu₂O/TNTs also exhibited augmented activity in degradation of target organic pollutant like acid orange (AO) under visible light irradiation. The ultra enhanced photocatalytic activity noticed by using Cu₂O/TNTs in CO₂ reduction and degradation of organic pollutant could be attributed to the formation of Cu₂O/TiO₂ heterostructures with higher charge separation efficiency.