Nitrogen Configuration Effects on Charge Carrier Dynamics in CsPbBr3/Carbon Dots S-Scheme Heterojunction for Photocatalytic CO2 Reduction.

Nitrogen-doped carbon dots (NCDs) featuring primary pyrrolic N and pyridinic N dominated configurations were prepared using hydrothermal (H-NCDs) and microwave (M-NCDs) methods, respectively. These H-NCDs and M-NCDs were subsequently applied to decorate CsPbBr3 nanocrystals (CPB NCs) individually, using a ligand-assisted reprecipitation process. Both CPB/M-NCDs and CPB/H-NCDs nanoheterostructures (NHSs) exhibited S-scheme charge transfer behavior, which enhanced their performance in photocatalytic CO2 reduction and selectivity of CO2-to-CH4 conversion, compared to pristine CPB NCs. The presence of pyrrolic N configuration at the heterojunction of CPB/H-NCDs facilitated efficient S-scheme charge transfer, leading to a remarkable 43-fold increase in photoactivity. In contrast, CPB/M-NCDs showed only a modest 3-fold enhancement in photoactivity, which was attributed to electron trapping by pyridinic N at the heterojunction. The study offers crucial insights into charge carrier dynamics within perovskite/carbon NHSs at the molecular level to advance the understanding of solar fuel generation.

Silica wastes derived multifunctional coatings for formaldehyde photodegradation and autonomous indoor humidity buffering.

To maintain a comfortable and healthy indoor environment without large amounts of energy consumption is of great importance. The progress of multifunctional indoor coatings with formaldehyde photodegradation and humidity buffering capability is necessary. From the viewpoints of circular economy, the preparation of effective photocatalysts (denoted as sFCC/GCN-x and ESF/GCN-y) via the decoration of recycling industrial wastes (i.e., spent fluid catalytic cracking catalysts (sFCC) and enhancement silica fume (ESF)) onto graphitic carbon nitride (GCN) by using a simple route is reported. The obtained results show that the prepared sFCC/GCN-0.15 and ESF/GCN-0.15 photocatalysts have the rate constants of formaldehyde degradation of 0.0075 and 0.0082 min-1, respectively, which are superior to that of pristine GCN (0.0044 min-1) under visible-light irradiation. The enhanced transfer kinetics of photogenerated electrons and declined recombination of electron-hole pairs may account for the surpassing photocatalytic performance. Results obtained from electron paramagnetic resonance spectra and Mott-Schottky plots indicate that the formation of ï½¥O2- via the reaction of O2 with electrons generated on the conduction band is the major reaction pathway to photodegrade formaldehyde under visible light. To further assess the real applications of prepared photocatalysts, the sFCC/GCN-0.15 and ESF/GCN-0.15 are used to fabricate the multifunctional coatings (denoted as s- and E-coatings) with sFCC and ESF as the main compositions. Experimentally, the E-coatings could reach the formaldehyde degradation efficiency of ca. 84.5% after 3 h of visible light irradiation and excellent humidity buffering ability (293.8 g m-2) which is at least 10-folds higher than commercial coatings (28.9 g m-2). This notable progress of humidity buffering capacity on E-coatings can be attributed to their surface textural properties. Most importantly, this study exemplifies the valorization of inorganic silica wastes to produce sustainable and multifunctional coatings which may offer the practical and cost-effective applications in the indoor living space.

Visible-Light Photocatalytic CO2-to-CO and H2O-to-H2O2 by g-C3N4/Cu2O-Pd S-Scheme Heterojunctions.

Visible-light photocatalytic conversion of CO2-to-fuels for green electricity is sustainably attractive for alleviating carbon emissions. Photocatalytic CO2-to-CO frequently suffered from relatively low yields, mainly due to ineffective charge transfer rates. A new approach for photocatalytic CO2-to-CO enhanced with effective H+ from H2O-to-H2O2 through the water oxidation reaction (WOR) has been studied in the present work. Here, the nano palladium (9 wt %), serving as a cocatalyst, dispersed on the g-C3N4/Cu2O heterojunctions (i.e., g-C3N4/Cu2O-Pd) has been prepared to facilitate charge separation for the two-electron reduction of CO2 to CO. Experimentally, the g-C3N4/Cu2O-Pd heterojunctions have a higher photocatalytic H2O-to-H2O2 yield than the g-C3N4/Cu2O heterojunction by 5.3 times. The photocatalytic WOR provides sufficient electrons (e-) and H+ (2H2O → H2O2 + 2H+) for CO2-to-CO (CO2(aq) + 2H+ + 2e- → CO(g) + H2O(l)). Relatively high photocatalytic yields of H2O2 (34.0 µmol/mg) and CO (14.6 µmol/mg) affected by the heterojunctions can be achieved. Also, the heterojunctions have a high photostability with a photocatalytic generated CO/H2 ratio of 1.75 approximately. This visible-light photocatalytic CO2-to-CO and H2O-to-H2O2 by the new g-C3N4/Cu2O-Pd S-scheme heterojunctions demonstrates the feasibility of the zero carbon emission approach with additional green oxidant (H2O2) generation.

Pseudocapacitive Deionization of Saltwater by Mn3O4@C/Activated Carbon.

Capacitive deionization (CDI), a m ethod with notable advantages of relatively low energy consumption and environmental friendliness, has been widely used in desalination of saltwater. However, due to the weak electrical double-layer electrosorption of ions from water, CDI has suffered from low throughput capacity that may limit its commercial applications. Thus, it is of importance to develop a high-efficiency and engineering-feasible CDI process. Manganese and cobalt and their oxides, being faradic materials, have a relatively high pseudocapacitance, which can cause an increase of positive and negative charges on opposing electrodes. However, their low conductivity properties limit their electrochemical applications. Pseudocapacitive Mn3O4 nanoparticles encapsulated within a conducting carbon shell (Mn3O4@C) were prepared to enhance charge transfer and capacitance for CDI. Desalination performances of the Mn3O4@C (5-15 wt %) core-shell nanoparticles on activated carbon (AC) (Mn3O4@C/AC) serving as CDI electrodes have thus been investigated. The pseudocapacitive Mn3O4@C/AC electrodes with relatively low diffusion resistances have much greater capacitance (240-1300 F/g) than the pristine AC electrode (120 F/g). In situ synchrotron X-ray absorption near-edge structure spectra of the Mn3O4@C/AC electrodes during CDI (under 1.2 and -1.2 V for electrosorption and regeneration, respectively) demonstrate that reversible faradic redox reactions cause more negative charges on the negative electrode and more positive charges on the positive electrode. Consequently, the pseudocapacitive electrodes for CDI of saltwater ([NaCl] = 1000 ppm) show much better desalination performances with a high optimized salt removal (600 mg/g·day), electrosorption efficiency (48%), and electrosorption capacity (EC) (25 mg/g) than the AC electrodes (288 mg/g·day, 23%, and 12 mg/g, respectively). The Mn3O4@C/AC electrode has a maximum EC of 29 mg/g for CDI under +1.2 V. Also, the Mn3O4@C/AC electrodes have much higher pseudocapacitive electrosorption rate constants (0.0049-0.0087 h-1) than the AC electrode (0.0016 h-1). This work demonstrates the feasibility of high-efficiency CDI of saltwater for water recycling and reuse using the low-cost and easily fabricated pseudocapacitive Mn3O4@C/AC electrodes.

Charge Carrier Dynamics of CsPbBr3/g-C3N4 Nanoheterostructures in Visible-Light-Driven CO2-to-CO Conversion.

The photon energy-dependent selectivity of photocatalytic CO2-to-CO conversion by CsPbBr3 nanocrystals (NCs) and CsPbBr3/g-C3N4 nanoheterostructures (NHSs) was demonstrated for the first time. The surficial capping ligands of CsPbBr3 NCs would adsorb CO2, resulting in the carboxyl intermediate to process the CO2-to-CO conversion via carbene pathways. The type-II energy band structure at the heterojunction of CsPbBr3/g-C3N4 NHSs would separate the charge carriers, promoting the efficiency in photocatalytic CO2-to-CO conversion. The electron consumption rate of CO2-to-CO conversion for CsPbBr3/g-C3N4 NHSs was found to intensively depend on the rate constant of interfacial hole transfer from CsPbBr3 to g-C3N4. An in situ transient absorption spectroscopy investigation revealed that the half-life time of photoexcited electrons in optimized CsPbBr3/g-C3N4 NHS was extended two times more than that in the CsPbBr3 NCs, resulting in the higher probability of charge carriers to carry out the CO2-to-CO conversion. The current work presents important and novel insights of semiconductor NHSs for solar energy-driven CO2 conversion.

Mechanisms of biochar enhanced Cu2O photocatalysts in the visible-light photodegradation of sulfamethoxazole.

Cu2O nanoparticles are decorated with biochars derived from spent coffee grounds (denoted as Cu2O/SCG) and applied as visible-light-active photocatalysts in the sulfamethoxazole (SMX) degradation. The physicochemical properties of Cu2O/SCG are identified by various spectral analysis, electrochemical and photochemical techniques. As a result, the Cu2O/SCG exhibits the higher removal efficiency of SMX than the pristine Cu2O under visible light irradiation. We can observe that Cu2O could be incorporated onto the SCG biochars with rich oxygen vacancies/adsorbed hydroxyl groups. In addition, the Cu2O/SCG has the lower charge transfer resistance, faster interfacial electron transfer kinetics, decreased recombination of charge carriers and superior absorbance of visible light. The construction of band diagrams for Cu2O/SCG and pristine Cu2O via UV-vis spectra and Mott-Schottky plots suggest that the band energy shifts and higher carrier density of Cu2O/SCG may be responsible for the photocatalytic activity enhancements. From the radical scavenger experiments and electron paramagnetic resonance spectra, the aforementioned energy shifts could decrease the energy requirement of transferring photoinduced electrons to the potential for the formation of active superoxide radicals (·O2-) via one and two-electron reduction routes in the photocatalytic reaction. A proposed degradation pathway shows that ·O2- and h+ are two main active species which can efficiently degrade SMX into reaction intermediates by oxidation, hydroxylation, and ring opening. This research demonstrates the alternative replacement of conventional carbon materials for the preparation of biochar-assisted Cu2O photocatalysts which are applied in the environmental decontamination by using solar energy.

Visible-Light Driven H2O-to-H2O2 Reaction by Nitrogen-Enriched Resins for Photocatalytic Oxidation of an Organic Pollutant in Wastewater.

A photocatalytic H2O-to-H2O2 reaction for sustainable organic wastewater treatment is environmentally attractive. Phenolic resins, inexpensive metal-free photocatalysts, are capable of harvesting visible light. Herein, novel nitrogen-enriched resin photocatalysts with a desired band-gap energy (1.83-1.98 eV) for harvesting visible light were prepared by copolymerization of resorcinol and melem for simultaneous photocatalytic H2O-to-H2O2 and oxidation of methylene blue. Under visible light irradiation for 5 h, very high yields of H2O2 (870-975 µM of H2O2/g/h) by RFM resin photocatalysts could be achieved. The photocatalytic H2O2 for reactive oxygen species (•OH) and photogenerated h+ could account for high conversion (40% conversion under visible light irradiation within 3 h) in oxidation of methylene blue. Such unique low-cost metal-free resins demonstrate the visible light photocatalytic H2O-to-H2O2 reaction which can synergize with the oxidation of organic pollutants in wastewater.

Selective recovery of platinum from spent autocatalyst solution by thiourea modified magnetic biocarbons.

The precious platinum group metals distributed in urban industrial products should be recycled because of their rapid decline in the contents through excessive mining. In this work, thiourea modified magnetic biocarbons are prepared via an energy-efficient microwave-assisted activation and assessed as potential adsorbents to recover platinum ions (i.e., Pt(IV)) from dilute waste solution. The physicochemical properties of prepared biocarbons are characterized by a series of spectroscopic and analytic instruments. The adsorption performance of biocarbons is carried out by using batch tests. Consequently, the maximum adsorption capacity of Pt(IV) observed for adsorbents is ca. 42.8 mg g-1 at pH = 2 and 328 K. Both adsorption kinetics and isotherm data of Pt(IV) on the adsorbents are fitted better with non-linear pseudo second-order model and Freundlich isotherm, respectively. Moreover, the thermodynamic parameters suggest that the Pt(IV) adsorption is endothermic and spontaneous. Most importantly, the adsorbents exhibit high selectivity toward Pt(IV) adsorption and preserve ca. 96.9% of adsorption capacity after six cyclic runs. After adsorption, the regeneration of the prepared adsorbents can be effectively attained by using 1 M thiourea/2% HCl mixed solution as an eluent. Combined the data from Fourier transform infrared and X-ray photoelectron spectroscopies, the mechanisms for Pt(IV) adsorption are governed by Pt-S bond between Pt(IV) and thiourea as well as the electrostatic attraction between anionic PtCl62- and cationic functional groups of adsorbents. The superior Pt(IV) recovery and sustainable features allow the thiourea modified magnetic biocarbon as a potential adsorbent to recycle noble metals from spent autocatalyst solution.

Photodecomposition of ibuprofen over g-C3N4/Bi2WO6/rGO heterostructured composites under visible/solar light.

A microwave-assisted hydrothermal preparation of heterostructured graphitic carbon nitride/bismuth tungsten oxide/reduced graphene oxide nanocomposites (denoted as GBR-T, T = microwave irradiation time) is performed. The prepared GBR-T photocatalysts are identified by employing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), time-resolved photoluminescence (TRPL) and nitrogen adsorption-desorption isotherms. The photocatalytic performance of these GBR-T is evaluated by the photocatalytic degradation of ibuprofen (IBP) under the visible light (λ > 420 nm) and solar light irradiation. Among all prepared photocatalysts, ca. 93% of IBP photodegradation can be achieved with a degradation rate constant (k) of 0.011 min-1 under visible-light irradiation upon the optimal microwave-assisted reaction time of 60 min. The improvement is primarily attributable to the higher crystallization degree, specific surface area and increased charge transfer efficiency as verified by XRD, nitrogen adsorption-desorption isotherms and TRPL, respectively. The photocatalytic performance of this catalyst is further enhanced in the photodecomposition of IBP (ca. 98.6%) under sun light irradiation. The electron spin resonance (ESR) and liquid chromatography-mass/mass spectrometry (LC-MS/MS) studies show that the superoxide radicals and hydroxyl radicals are the dominant active species in the photocomposition of IBP and degradation intermediates are formed through three probable photodegradation pathways. This investigation provides a simple way to prepare triple 2D heterojuction photocatalysts which could be effectively used in the advanced oxidation process for removal of emerging contaminants in wastewater by using renewable energy.

Microwave-assisted production of CO2-activated biochar from sugarcane bagasse for electrochemical desalination.

A high-performance carbon electrode is desirable for promoting electrochemical desalination efficiency in the membrane capacitive deionization (MCDI). Sugarcane bagasse (food waste) was employed in this study to prepare hierarchically porous biochars by microwave-assisted carbonization and activation with potassium hydroxide in N2 or CO2 atmosphere under varying flow rates (100-600 cm3 min-1). The sugarcane bagasse-derived biochars activated under CO2 flow of 300 cm3 min-1 (denoted as SBB-CO2-300) possessed the ratio of mesopores to total pore volume (Vmeso/Vtotal) of 56.7% with a specific surface area of 1019 m2 g-1. The electrochemical behavior of SBB-CO2-300 was demonstrated by a surpassing specific capacitance of 208 F g-1 at 5 mV s-1 by means of cyclic voltammetry. The desalination tests using a batch-mode MCDI at 1.2 V in a 5 mM NaCl solution indicated that the SBB-CO2-300 electrode exhibited an excellent electrosorption capacity of 28.9 mg g-1. The improvement in the electrochemical deionization performance of SBB-CO2-300 was attributed to the superior Vmeso/Vtotal ratio, high surface area, excellent capacitance behavior, and hierarchical pore structure. The biowaste-derived biochars prepared via facile microwave-assisted carbonization and CO2 activation route can provide a sustainable and high-efficiency carbon electrode for electrochemical deionization of brackish water.

A simple method to prepare g-C3N4-TiO2/waste zeolites as visible-light-responsive photocatalytic coatings for degradation of indoor formaldehyde.

The indoor air quality should be highly addressed because people spend more time staying in indoor environments. Photocatalytic degradation of indoor pollutants (e.g., formaldehyde) is one of the most promising and environmental friendly technologies. In this work, a heterostructured photocatalyst combining graphitic carbon nitride (g-C3N4), TiO2 and waste zeolites (g-C3N4-TiO2/waste zeolites) is developed by a facile calcination and sol-gel method. The prepared photocatalysts exhibit the superior visible-light-responsive activities toward formaldehyde degradation (k = 0.0127 min-1) which is higher than g-C3N4-TiO2 (k = 0.0123 min-1) and P25 (k = 0.0056 min-1). Over 90% of low-concentration formaldehyde can be oxidized by g-C3N4-TiO2/waste zeolites under a commercial LED light within 300 min. The electron spin resonance spectra indicate that the superoxide radical anions (O2-) photogenerated on the g-C3N4-TiO2/waste zeolites under visible light irradiation are responsible for the decomposition of formaldehyde. The enhancement in the photocatalytic decomposition of formaldehyde in the air is possibly due to the heterojunction between g-C3N4 (the enhanced absorption of visible light) and TiO2 (fast transfer of photogenerated electrons from g-C3N4) as well as assisted adsorption of gas-phase formaldehyde via waste zeolites. This work also exemplifies the valorization of industrial silicate wastes to efficient photocatalytic coatings for indoor air purification.

SnO2/TiO2 nanotube heterojunction: The first investigation of NO degradation by visible light-driven photocatalysis.

Titania (TiO2) as a commercial photocatalyst has been continually struggling due to the limitation of ultraviolet light response and the high recombination rate of photoinduced carriers. The development of heterojunction nanostructures provides great promise to achieve the activation by visible light and suppress the photoinduced electron-hole pairs recombination. Herein, we synthesized a SnO2 and TiO2 nanotube heterojunction (SnO2/TNT) via a one-step hydrothermal strategy and systematically investigated NO photocatalytic degradation over the SnO2/TNTs heterojunction under visible light at the parts per billion level. Various physicochemical characterization techniques were conducted to verify the physical and chemical properties of the materials. For example, the morphology and lattice spacings of the materials were examined by high-resolution TEM (HR-TEM) images and selected area electron diffraction (SAED) pattern, X-ray photoelectron spectroscopy (XPS) was employed to study the oxidation states and propose the band alignment diagram of the SnO2/TNTs heterojunction, and photoluminescence spectroscopy was employed for understanding of carrier's trapping, migration and transfer. The photocatalytic results show that the SnO2/TNTs heterojunction exhibits the superior photocatalytic performance, and the photocatalytic degradation efficiency of NO can reach 60% under visible light with effective inhibition of NO2 production. The excellent photocatalytic ability is due to the low recombination rate of the photoinduced electron-hole pairs. Furthermore, a trapping experiment was combined with electron spin resonance (ESR) and utilized to identify the involvement of reactive radicals in the photocatalysis process suggesting that and OH mediated pathways play a predominant role in NO removal.

Adsorption of nicotine in aqueous solution by a defective graphene oxide.

Extensive concerns have been focused on the emerging contaminants including nicotine in the aquatic system recently. Graphene oxide (GO) and modified graphene oxides (GO-COOH and defective GO-COOH) are used as effective adsorbents to remove nicotine from aqueous solution. The adsorption isotherms and kinetics of the adsorbents all fit well with Langmuir model and pseudo-second-order model, respectively. The thermodynamic studies show that the adsorption is an exothermic and spontaneous process. The influence of pH and ionic solution strength on the adsorbents is also investigated. The maximum adsorption capacity can be observed at pH value of ca. 8. The adsorption capacities of nicotine are decreased upon the increase of sodium ion concentration. Among all the adsorbents, the defective GO-COOH adsorbents possess the maximum adsorption capacity of nicotine of 196.5 mg g-1 obtained from Langmuir isotherm. In regeneration experiments, the defective GO-COOH adsorbents can maintain 95.1% of adsorption capacity after five times of cyclic adsorption-desorption processes. The adsorbents are identified by Fourier transform infrared, 13C solid-state magic-angle spinning nuclear magnetic resonance, X-ray photoelectron and Raman spectroscopies to determine the adsorption mechanisms and structure on the adsorbents. It can be deduced that the surpassing performance of defective GO-COOH may be ascribed to the unique adsorption mechanism of defects, the enhanced π-π interaction and cation-π bonding. The highly-efficient and stable features enable the defective GO-COOH a promising adsorbent to eliminate nicotine from water.

Facet-Dependent Cuprous Oxide Nanocrystals Decorated with Graphene as Durable Photocatalysts under Visible Light.

Three morphologies (octahedral, hierarchical and rhombic dodecahedral) of crystal Cu2O with different facets ({111}, {111}/{110}, and {110}) incorporating graphene sheets (denoted as o-Cu2O-G, h-Cu2O-G and r-Cu2O-G, respectively) have been fabricated by using simple solution-phase techniques. Among these photocatalysts, the r-Cu2O-G possesses the best photocatalytic performance of 98% removal efficiency of methyl orange (MO) with outstanding kinetics for 120 min of visible light irradiation. This enhancement is mainly due to the dangling “Cu” atoms in the highly active {110} facets, resulting in the increased adsorption of negatively charged MO. More importantly, the unique interfacial structures of Cu2O rhombic dodecahedra connected to graphene nanosheets can not only decrease the recombination of electron-hole pairs but also stabilize the crystal structure of Cu2O, as verified by a series of spectroscopic analyses (e.g., X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)). The effective photocatalysts developed in this work could be applied to the efficient decolorization of negatively charged organic dyes by employing solar energy.

Highly visible-light-responsive Cu2O/rGO decorated with Fe3O4@SiO2 nanoparticles as a magnetically recyclable photocatalyst.

The rhombic dodecahedral cuprous oxide-reduced graphene oxide/core-shell Fe3O4@SiO2 composites (denoted as rCu2O-rGO/Fe3O4@SiO2) are successfully synthesized facilely via a wet-chemical route. The resulting rCu2O-rGO/Fe3O4@SiO2 combines the unique structure of Cu2O, electronic characteristics of reduced graphene oxide (rGO) and magnetic property of Fe3O4@SiO2 to be an effective and recoverable photocatalyst for the degradation of methyl orange (MO). The obtained results show that rCu2O-rGO/Fe3O4@SiO2 is capable of completely degrading MO in the presence of a very low catalyst concentration (0.125 g l-1) within a short time (60 min) under visible light compared to the reported catalysts. The observations may be due to the distinctive interfacial structures of rhombic dodecahedral Cu2O nanoparticles connected to rGO sheets that can enhance the separation of photogenerated electron-hole pairs, stabilize the Cu2O and increase MO adsorption, as evidenced by a variety of spectroscopic analyses (transmission electron microscopy, x-ray photoelectron spectroscopy and photoluminescence). More importantly, these efficient photocatalysts can easily be recovered under a magnetic field and remain highly photoactive towards the degradation of MO after cyclic tests, and may be promising photocatalysts for practical applications in the solar-energy purification of wastewater.

Preparation of stable tetraethylenepentamine-modified ordered mesoporous silica sorbents by recycling natural Equisetum ramosissimum.

It is well-known that global warming of the earth is caused by the progressive increase of CO2 concentration in the environment due to the huge utilization of fossil fuels. As a result, the development of an efficient and economic method to capture CO2 from large stationary sources, such as coal-fired power plants, cement and steel factories, and so on is urgent. In this study, ordered mesoporous silicas (E-SBA-15) have been prepared by using Equisetum ramosissimum plants as the silica sources and their subsequently incorporating with amino-containing compounds (tetraethylenepentamine, TEPA) and stabilizers (titanium isopropoxide, TIP). A variety of different spectroscopic and analytical techniques, such as nitrogen adsorption-desorption isotherms, low-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transformed infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) are used to characterize the physicochemical properties of various materials. CO2 adsorption capacities of prepared sorbents at 75 °C are obtained by TGA at atmospheric pressure. Among all sorbents, TEPA impregnated E-SBA-15 sorbents possess the highest CO2 sorption capacity (1.60 mmol CO2 g-1sorbent) under ambient pressure using dry 15% CO2. However, TEPA/TIP incorporated E-SBA-15 sorbents exhibit enhanced durability during repeated sorption-desorption cycles compared to the above-mentioned sorbents. This significant enhancement in the stability of CO2 sorption-desorption process is most likely due to the decreased decomposition/leaching of TEPA which is restricted via the steric effect of TIP. These synthesized sorbents from inexpensive resources (agricultural waste) exhibit good sorbent capacity and surpassing regenerability, revealing a promising CO2 sorbent for the cost-effective applications in a cyclic adsorption process.

Dual Alkali Solvent System for CO2 Capture from Flue Gas.

A novel two-aqueous-phase CO2 capture system, namely the dual alkali solvent (DAS) system, has been developed. Unlike traditional solvent-based CO2 capture systems in which the same solvent is used for both CO2 absorption and stripping, the solvent of the DAS system consists of two aqueous phases. The upper phase, which contains an organic alkali 1-(2-hydroxyethyl) piperazine (HEP), is used for CO2 absorption. The lower phase, which consists of a mixture of K2CO3/KHCO3 aqueous solution and KHCO3 precipitate, is used for CO2 stripping. Only a certain kind of amine (such as HEP) is able to ensure the phase separation, satisfactory absorption efficiency, effective CO2 transfer from the upper phase to the lower phase, and regeneration of the upper phase. In the meantime, due to the presence of K2CO3/KHCO3 in the lower phase, HEP in the upper phase is capable of being regenerated from its sulfite/sulfate heat stable salt, which enables the simultaneous absorption of CO2 and SO2/SO3 from the flue gas. Preliminary experiments and simulations indicate that the implementation of the DAS system can lead to 24.0% stripping energy savings compared to the Econamine process, without significantly lowering the CO2 absorption efficiency (∼90%).

Visible-light-driven photodegradation of sulfamethoxazole and methylene blue by Cu2O/rGO photocatalysts.

The cuprous oxide-reduced graphene oxide (Cu2O/rGO-x) composites were prepared via a simple wet-chemical method by using CuSO4·5H2O and graphene oxide as precursors and ascorbic acid as a reducing agent, respectively. These Cu2O/rGO-x were employed as photocatalysts for degrading emerging contaminants and organic dye pollutants (i.e., sulfamethoxazole (SMX) and methylene blue (MB)) under visible light. A variety of different spectroscopic and analytical techniques, such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman scattering spectroscopy and UV-Visible spectroscopy were used to characterize the physical properties of photocatalysts. In the photodegrading experiments, it can be found that the Cu2O/rGO-80 photocatalyst has the superior visible-light response of ca. 50% removal efficiency of SMX within 120 min and 100% removal efficiency of MB within 40 min. These observations may be attributed the well-dispersed and visible-light-responsive Cu2O nanoparticles are supported on the surface of rGO sheets that can enhance absorption of visible light during photocatalysis.

Spectroscopic studies of heat-treated FeNxCy/C involved in electrochemical oxygen reduction under acid media.

Carbon-incorporated FeNx electrocatalysts (FeNC/C-T) have been synthesized by carbonizing a nitrogen-containing specie and iron precursor on carbon blacks at various heat-treated temperatures. The catalyst properties (crystalline structure, surface chemical states, oxidation state and co-ordination geometry) and their formation scheme of FeNC/C-T have been thoroughly examined by X-ray based spectroscopies such as X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The electrochemical performance of oxygen reduction reaction (ORR) and methanol tolerance were also investigated by rotating disk electrode tests in 0.5M H2SO4. By combined results from XPS and XAS spectroscopies, the catalysts carbonized at 1073K possess higher surface Fe/C and N/C atomic ratios with formation of carbons incorporated FeN4 species were found to have the optimal electrocatalytic properties.

Synthesis, characterization and photocatalytic performance of self-assembled mesoporous TiO2 nanoparticles.

A facile synthesis route is reported for preparation of mesoporous TiO(2) nanoparticles (MT-x) through evaporation induced self-assembly by using Pluronic F127, titanium isopropoxide, and various amounts of ethanol as templating agents, titanium sources and solvents, respectively. A variety of different spectroscopic and analytical techniques, such as small- and large-angle powder X-ray diffraction (XRD), N(2) adsorption-desorption isotherms, transmission electron microscopy (TEM), Raman and Fourier transform infrared (FTIR) spectroscopies were used to characterize the physicochemical properties of various MT-x catalysts. Among the catalysts, MT-20 was found to have better mesostructures formed by the arrangement of anatase TiO(2) nanoparticles of ca. 17.3 nm with broad interparticle pore size distribution. Hydrogen generation from water splitting on MT-20 using visible light was enhanced by at least 8.7 times if compared with the conventional TiO(2) photocatalyst. The superior photocatalytic performances observed for the synthesized MT-20 may be attributed to the presence of unique nanostructures in the TiO(2) photocatalysts.