Innovative Thermocatalytic H2 Sensor with Double-Sided Pd Nanocluster Films on an Ultrathin Mica Substrate.

Hydrogen (H2) is crucial in the future global energy landscape due to its eco-friendly properties, but its flammability requires precise monitoring. This study introduces an innovative thermocatalytic H2 sensor utilizing ultrathin mica sheets as substrates, coated on both sides with Pd nanocluster (NC) films. The ultrathin mica substrate ensures robustness and flexibility, enabling the sensor to withstand high temperatures and mechanical deformation. Additionally, it simplifies the fabrication process by eliminating the need for complex microelectro-mechanical systems (MEMS) technology. Constructed through cluster beam deposition, the sensor exhibits exceptional characteristics, including a wide concentration range (from 500 ppm to 4%), rapid response and recovery times (3.1 and 2.4 s for 1% H2), good selectivity, high stability, and repeatability. The operating temperature can be as low as 40 °C, achieving remarkably low power consumption. The study explores the impact of double-sided versus single-sided catalytic layers, revealing significantly higher sensitivity and response with the double-sided configuration due to the increased catalytic surface area. Additionally, the research investigates the relationship between the deposition amount of Pd NCs and the sensor's sensitivity, identifying an optimal value that maximizes performance without excessive use of Pd. The sensor's innovative design and excellent performance position it as a promising candidate for meeting the demands of a hydrogen-based energy economy.

Development of Pd/In2O3 hybrid nanoclusters to optimize ethanol vapor sensing.

In this study, we successfully synthesize palladium-decorated indium trioxide (Pd/In2O3) hybrid nanoclusters (NCs) using an advanced dual-target cluster beam deposition (CBD) method, a significant stride in developing high-performance ethanol sensors. The prepared Pd/In2O3 hybrid NCs exhibit exceptional sensitivity, stability, and selectivity to low concentrations of ethanol vapor, with a maximum response value of 101.2 at an optimal operating temperature of 260 °C for 6 at% Pd loading. The dynamic response of the Pd/In2O3-based sensor shows an increase in response with increasing ethanol vapor concentrations within the range of 50 to 1000 ppm. The limit of detection is as low as 24 ppb. The sensor exhibits a high sensitivity of 28.24 ppm-1/2, with response and recovery times of 2.7 and 4.4 seconds, respectively, for 100 ppm ethanol vapor. Additionally, the sensor demonstrates excellent repeatability and stability, with only a minor decrease in response observed over 30 days and notable selectivity for ethanol compared to other common volatile organic compounds. The study highlights the potential of Pd/In2O3 NCs as promising materials for ethanol gas sensors, leveraging the unique capabilities of CBD for controlled synthesis and the catalytic properties of Pd for enhanced gas-sensing performance.

A Universal Self-Propagating Synthesis of Aluminum-Based Oxyhalide Solid-State Electrolytes.

Inorganic solid-state electrolytes (SSEs) play a vital role in high-energy all-solid-state batteries (ASSBs). However, the current method of SSE preparation usually involves high-energy mechanical ball milling and/or a high-temperature annealing process, which is not suitable for practical application. Here, a facile strategy is developed to realize the scalable synthesis of cost-effective aluminum-based oxyhalide SSEs, which involves a self-propagating method by the exothermic reaction of the raw materials. This strategy enables the synthesis of various aluminum-based oxyhalide SSEs with tunable components and high ionic conductivities (over 10-3 S cm-1 at 25 °C) for different cations (Li+, Na+, Ag+). It is elucidated that the amorphous matrix, which mainly consists of various oxidized chloroaluminate species that provide numerous sites for smooth ion migration, is actually the key factor for the achieved high conductivities. The application of these aluminum-based oxyhalide SSEs synthesized by our approach further pushes forward their practical application considering their easy synthesis, low cost, and low weight that ensures high-energy-density ASSBs.

The construction of lattice-matched CdS-Ag2S heterojunction photocatalysts: High-intensity built-in electric field effectively boosts bulk-charge separation efficiency.

The built-in electric field of heterojunction can effectively promote carrier separation and transfer. While, its interface orientation is often random, leading to lattice mismatch and high resistance, thus limiting the efficiency of interfacial charge transfer. Herein, the lattice-matched heterojunction (CdS-Ag2S) was constructed by ion-exchange epitaxial growth. The results of surface photovoltage spectroscopy (SPV), transient photovoltage spectroscopy (TPV), and time-resolved photoluminescence (TRPL) show that the lattice-matched heterojunction has higher charge separation efficiency and longer photogenerated carrier lifetime than that of lattice-mismatched one. The lattice-matched CdS-Ag2S has a high built-in electric field (BIEF) value of 103.42 and a bulk-charge separation (BCS) efficiency of 68.71%, which is about three times higher than that of the lattice-mismatched heterojunction (CdS-Ag2S-M). In addition, the photodegradation efficiency of CdS-Ag2S towards norfloxacin (NOR) was also 3.4 times higher than that of CdS-Ag2S-M. The above results and density functional theory (DFT) calculations indicate that improving the lattice matching at the heterojunction is beneficial for establishing a high-intensity built-in electric field and effectively promoting bulk-charge separation efficiency, thus achieving excellent photocatalytic performance. This work provides an essential reference for the research of high-performance heterojunction photocatalysts.

Theoretical Study on the Swelling Mechanism and Structural Stability of Ni3Al-LDH Based on Molecular Dynamics.

layered double hydroxide (LDH) as a kind of 2D layer material has a swelling phenomenon. Because swelling significantly affects the adsorption, catalysis, energy storage, and other application properties of LDHs, it is essential to study the interlayer spacing, structural stability, and ion diffusion after swelling. In this paper, a periodic computational model of Ni3Al-LDH is constructed, and the supramolecular structure, swelling law, stability, and anion diffusion properties of Ni3Al-LDH are investigated by molecular dynamics theory calculations. The results show that the interlayer water molecules of Ni3Al-LDH present a regular layered arrangement, combining with the interlayer anions by hydrogen bonds. As the number of water molecules increases, the hydrogen bond between the anion and the basal layer gradually weakens and disappears when the number of water molecules exceeds 32. The hydrogen bond between the anion and the water molecule gradually increases, reaching an extreme value when the number of water molecules is 16. The interlayer spacing of Ni3Al-LDH is not linear with the number of water molecules. The interlayer spacing increases slowly when the number of water molecules is more than 24. The maximum layer spacing is stable at around 19 Å. The interlayer spacing, binding energy, and hydration energy show an upper limit for swelling: the number of water molecules is 32. When the number of interlayer water molecules is 16, the water molecules' layer structure and LDH interlayer spacing are suitable for anions to obtain the maximum diffusion rate, 10.97 × 10-8 cm2·s-1.

Construction dual vacancies to regulate the energy band structure of ZnIn2S4 for enhanced visible light-driven photodegradation of 4-NP.

Most of the intrinsic photocatalysts with visible light response can only generate one active radical due to the limitation of their band structures, which is immediate cause limiting their photocatalytic degradation performance. In this work, ZnIn2S4 with Zn vacancy and S vacancy (VZn+S-ZnIn2S4) was prepared for the first time. As expected, the VZn+S-ZnIn2S4 exhibits remarkable photocatalytic performance for 4-Nitrophenol (4-NP) degradation under visible light and the apparent rate constant is about 11 times that of pristine ZnIn2S4. The construction of dual vacancies can regulate the energy band structure of the ZnIn2S4, enabling it to generate •OH and •O2- simultaneously. Meanwhile, dual vacancies system can also extremely improve the separation efficiency of carriers. It is worth noting that Zn vacancy and S vacancy can capture photogenerated holes and photogenerated electrons, respectively, which is beneficial for photogenerated carriers to participate in radical generation reactions. In addition, a possible 4-NP degradation pathway was proposed based on HPLC-MS analysis. This work provides a new way to construct photocatalysts for photodegradation of pollutants in wastewater.

CNT/PVDF Composite Coating Layer on Cu with a Synergy of Uniform Current Distribution and Stress Releasing for Improving Reversible Li Plating/Stripping.

The uncontrollable formation of polymorphous Li deposits, e.g., whiskers, mosses, or dendrites resulting from nonuniform interfacial current distribution and internal stress release in the upward direction on the conventional current collector (e.g., Cu foil) of Li metal rechargeable batteries with a lithium-metal-free negatrode (LMFRBs), leads to rapid performance degradation or serious safety problems. The 3D carbon nanotubes (CNTs) skeleton has been proven to effectively reduce the current density and eliminate the internal accumulated stress. However, remarkable electrolyte decomposition, inherent Li source consumption due to repeated SEI formation, and Li+ intercalation in CNTs limit the application of 3D CNTs skeleton. Thus, it is necessary to avoid the side effects of the 3D CNTs skeleton and retain uniform interfacial current distribution and stress mitigation. In this work, we integrate the CNTs network with a soft functional polymer polyvinylidene fluoride (PVDF) to form a relatively dense coating layer on Cu foil, which can shield the contact between the internal surface of the 3D CNTs framework and the electrolyte. Simultaneously, the Li-F-rich SEI resulting from the partial reduction of PVDF with deposited Li and the soft nature of the coating layer release the accumulation of internal stress in the horizontal direction, resulting in mosses/whisker-free Li deposition. Thus, improved Li deposition/dissolution and stable cycling performance of the LMFRBs can be achieved.

High-Efficiency Photocatalytic Ammonia Synthesis by Facet Orientation-Supported Heterojunction Cu2O@BiOCl[100] Boosted by Double Built-In Electric Fields.

In this work, the advantages of in situ loading, heterojunction construction, and facet regulation were integrated based on the poly-facet-exposed BiOCl single crystal, and a facet-oriented supported heterojunction of Cu2O and BiOCl was fabricated (Cu2O@BiOCl[100]). The photocatalytic nitrogen reduction reaction (pNRR) activity of Cu2O@BiOCl[100] was as high as 181.9 µmol·g-1·h-1, which is 4.09, 7.13, and 1.83 times that of Cu2O, BiOCl, and Cu2O@BiOCl-ran (Cu2O randomly supported on BiOCl). Combined with the results of the photodeposition experiment, X-ray photoelectron spectroscopy characterization, and DFT calculation, the mechanism of Cu2O@BiOCl[100] for pNRR was discussed. When Cu2O directionally loaded on the [100] facet of BiOCl, electrons generated by Cu2O will be transmitted to the [100] facet of BiOCl through Z-scheme electron transmission. Due to the directional separation characteristics of charge in BiOCl, the electrons transmitted from Cu2O are enriched on the [001] facet of BiOCl, which will together with the original electrons generated by pristine BiOCl act on pNRR, thus greatly improving the activity of photocatalytic ammonia synthesis. Thus, a new construction scheme of biphasic semiconductor heterojunction was proposed, which provides a reference research idea for designing and synthesizing high-performance photocatalysts for nitrogen reduction.

Metal Nanocluster-Metal Organic Framework-Polymer Hybrid Nanomaterials for Improved Hydrogen Detection.

The development of hydrogen sensors is of paramount importance for timely leak detection and remains a crucial unmet need. Palladium-based materials, well known as hydrogen sensors, still suffer from poisoning and deactivation. Here, a hybrid hydrogen sensor consisting of a Pd nanocluster (NC) film, a metal-organic framework (MOF), and a polymer, are proposed. The polymer coating, as a protection layer, endows the sensor with excellent H2 selectivity and CO-poisoning resistance. The MOF serves as an interface layer between the Pd NC film and the polymer layer, which alters the nature of the interaction with hydrogen and leads to significant sensing performance improvements, owing to the interfacial electronic coupling between Pd NCs and the MOF. The strategy overcomes the shortcomings of retarded response speed and degraded sensitivity induced by the polymer coating of a Pd NC film-polymer hybrid system. This is the first exhibition of a hydrogen-sensing enhancement mechanism achieved by engineering the electronic coupling between Pd and a MOF. The work establishes a deep understanding of the hydrogen-sensing enhancement mechanism at the nanoscale and provides a feasible strategy to engineer next-generation gas-sensing nanodevices with superior sensing figures of merit via hybrid material systems.

Fabrication of ZnAl-LDH mixed metal-oxide composites for photocatalytic degradation of 4-chlorophenol.

In this work, two different types of ZnAl-layered double hydroxide (LDH) mixed metal-oxide composites (CeO2 and SnO2) were synthesized and applied for the photodegradation of 4-chlorophenol (4-CP) in wastewater. The fabricated CeO2/ZnAl-LDH and SnO2/ZnAl-LDH were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and theoretical density functional theory (DFT) calculations, suggesting that the band gaps of the synthesized hybrid composites were much lower than those of traditional ZnAl-LDH. In addition, the photocatalytic activity for 4-CP degradation and reaction kinetics were investigated to evaluate the catalytic behavior of the prepared composites. The results indicated that the photocatalytic process in this case followed a pseudo-first-order kinetic model, and SnO2/ZnAl-LDH illustrated the optimum performance for 4-CP degradation with an efficiency of 95.2% due to its stability and recyclability. Additionally, the reaction mechanism of 4-CP photodegradation was studied over SnO2/ZnAl-LDH; it presented that 4-CP could be oxidized by hydroxyl radicals, holes, and superoxide radicals, where hydroxyl radicals were identified as the dominant active species during the degradation process. Finally, decomposition intermediates were measured to deduce the reaction pathway of 4-CP, and three tentative pathways were proposed and discussed.

Lithium/Graphene Composite Anode with 3D Structural LiF Protection Layer for High-Performance Lithium Metal Batteries.

Lithium metal batteries (LMBs) are a promising candidate for next-generation energy storage devices. However, the high irreversibility and dead Li accumulation of the lithium metal anode caused by its fragile original solid electrolyte interface (SEI) seriously hinder the practical application of LMBs. Herein, a facile slurry-coating and one-step thermal fluorination reaction method is proposed to construct the 3D structural LiF-protected Li/G composite anode. The existence of a 3D LiF protection layer is convincingly confirmed and the function of the Li/G skeleton is discussed in detail. The 3D structural LiF protection layer results in superior electrochemical performance by improving the utilization of Li and suppressing the accumulation of dead Li in symmetric and full coin cells. Moreover, a 0.85 Ah pouch cell strictly following the parameters of the practical battery industry can work stably for 140 cycles with a gradual internal resistance increase. This novel Li/G composite anode indicates a promising strategy in lithium/carbon composite anodes for LMBs, and the facile thermal fluorination reaction method presented in this paper offers a new method for the construction of a 3D structural protection layer for lithium metal anodes.

3D hollow Bi2O3@CoAl-LDHs direct Z-scheme heterostructure for visible-light-driven photocatalytic ammonia synthesis.

In this paper, the novel 3D hollow Z-scheme heterojunction photocatalysts based on Bi2O3 and CoAl layered double hydroxides (Bi2O3@CoAl-LDHs) were prepared for efficient visible-light-driven photocatalytic ammonia synthesis. The synthesized nanohybrid exhibits excellent photocatalytic ammonia synthesis performance (48.7 µmol·L-1·h-1) and structural stability, which is primarily attributed to the fact that Z-scheme heterojunction significantly enhanced lifetime of photogenerated carriers (6.22 ns) and transfer efficiency of surface photogenerated electrons (72.5%). Strict control experiments and nitrogen isotope labeling results show that nitrogen and hydrogen in the produced ammonia come from nitrogen and water in the reactant respectively. Electron paramagnetic resonance (EPR) experiments and density functional theory (DFT) calculations further reveal that the built-in electric field due to the difference between Bi2O3 and CoAl-LDHs is the key to constructing the Z-scheme heterojunction. In addition, results of partial density of states (PDOS) show that Co in Bi2O3@CoAl-LDHs composite is the active site for photocatalytic N2 fixation.

Impacts of solvation on photo-damage of polypeptides: Modulation and biological implications.

We investigate the photon/matter interactions between soft X-rays and three selected polypeptides, poly-glycine (poly-Gly), poly-L-arginine (poly-Arg), and poly-l-lysine (poly-Lys), where the effects of molecular packing under the influence of solvent, e.g., water, substrates (Au foil or Si wafer) and X-ray irradiation under different durations were systematically investigated. Compared with negligible photo-damage on bare polypeptide powders, significantly enhanced degradation in pre-solvated polypeptides was observed likely because of the formation photo-generated radicals. X-ray photoemission spectroscopy (XPS) were employed as the analysis means to identify and quantify the chemical changes, especially the high-resolution photoemission spectra of C 1s, O 1s, N 1s and their evolution under continuous X-ray irradiation. The photo-degradation was found to preferentially occur on the CO entity in poly-Gly and the guanidinium group in poly-Arg. In poly-Arg, deprotonation occurs via the switch from zwittterionic to a neutral configuration, whereas poly-Lys deprotonates by directly losing the corresponding amine. The critical role of the interactions between amino acids, the building blocks of protein and almost all forms of biological activities, and the free-radical-generating living environment under irradiation was critically analyzed. The present study found that the preparation history of a sample, especially its inadvertent exposure to the sources of H2O, O2 and OH, could significantly alter the outcome of a radiation-related chemical process. Implications on the non-destructive probe of biologically important systems using physical methods involving X-rays were discussed as well.

Direct Z-scheme CeO2@LDH core-shell heterostructure for photodegradation of Rhodamine B by synergistic persulfate activation.

Photocatalytic activation of persulfate (PAPS) is considered an efficient and green approach for the mitigation of organic pollutants because of its advantages in low energy consumption and high reusability of photocatalysts. Herein, direct Z-scheme CeO2@LDH heterojunction photocatalyst with a core-shell structure is constructed. We reveal that CeO2@LDH exhibits excellent persulfate (PS) activation performance and high degradation efficiency of RhB under visible light irradiation. Control experiments by quenching catalytically active radicals and analysis of electron paramagnetic resonance (ESR) spectra suggest that the sulfate radical (SO4·-) generated by photocatalytic activation of PS, together with superoxide radical (·O2-) and hydroxyl radical (·OH), degrade pollutants synergistically. Density functional theory (DFT) calculations indicate that the built-in electric field across the surface of CeO2 and LDH is the intrinsic driving force for the efficient transfer of hot carriers in the Z-scheme heterojunction. The construction of this transfer path can effectively engineer the interfacial band structure and inhibit the recombination of photogenerated electron-hole pairs and promote their transportation. Meanwhile, electrons were found to accumulate at the conduction band (CB) of LDHs and holes populate at valence band (VB) of CeO2, generating more active species for photodegradation of RhB. We demonstrate that the Z-scheme heterojunction photocatalyst activated PS system (Z-scheme/PS) is a promising method to degrade RhB and potentially organic pollutants in general.

Experimental and Theoretical Investigations into the Performance and Mechanism of CO2 Capture by 3D and 2D ZnAl Layered Double Hydroxides.

Two-dimensional (2D) materials have a wide range of applications in adsorption and catalysis because of their high specific surface areas and large number of surface active sites. In this paper, bulk ZnAl layered double hydroxides (ZnAl-LDHs or bulk-LDHs) and 2D monolayer ZnAl-LDHs (monolayer-LDHs) were constructed and used for CO2 capture at temperatures of 298-573 K. The experimental results show that monolayer-LDHs have a large specific surface area (455 m2 g-1) and shows an excellent CO2 capture performance (4.5 mmol g-1). The CO2 adsorption capacity of monolayer-LDHs decreases greatly with an increase of the temperature, while bulk-LDHs are less affected by the temperature. Moreover, the parameters of charge distribution, density of states, and charge transfer of bulk-LDHs and monolayer-LDHs were studied in detail by density functional theory, and the difference of the adsorption mechanism between two LDH materials in CO2 capture was compared. It is found that monolayer-LDHs have better electronic activity than bulk-LDHs. At low temperature, CO2 is more likely to be physically adsorbed on the surface of monolayer-LDHs, and the adsorption process is more likely to occur. CO2 is more easily adsorbed on the surface of bulk-LDHs in the form of chemisorption, the adsorption energy is larger (-1.01 eV), but the CO2 capture capacity is quite stable at high temperature.

A low-temperature water-gas shift reaction catalyzed by hybrid NiO@NiCr-layered double hydroxides: catalytic property, kinetics and mechanism investigation.

The realization of a high efficiency water gas shift reaction (WGSR) at low temperatures has always been a research hotspot and is difficult to achieve. Based on NiCr layered double hydroxides (NiCr-LDHs), a hybrid NiO@NiCr-LDH was prepared by intercalation and surface complexing. The above materials were applied to WGSR at low temperatures, and the catalytic activity and reaction mechanism of WGSR with NiCr-LDHs and LDHs intercalated with organic metal ligands (NiCr-Ni/SB-LDHs) were compared. It was found that the activity of NiO@NiCr-LDHs was about 4 and 2 times higher than that of NiCr-LDHs and NiCr-Ni/SB-LDHs, respectively. At 150 °C, the CO conversion of NiO@NiCr-LDHs is 35.2%, the reaction rate is 19.71 µmol gcat-1 s-1, the TOF value is 0.225 s-1, and the activation energy is 77.4 kJ mol-1. In addition, the complexing NiO content has a great influence on the activity of NiO@NiCr-LDHs for WGSR. In addition, DFT calculations were used to compare the differences in the performance and catalytic mechanism of different nickel containing LDH catalysts for WGSR. According to the calculated results of relative energy barrier and activation energy, a possible reaction pathway and mechanism are discussed. The results show that compared with NiCr-LDHs and NiCr-Ni/SB-LDHs, NiO@NiCr-LDHs can effectively reduce the activation energy of the H2O dissociation step, which is the rate determining step of WGSR.

Visible light promoted degradation of gaseous volatile organic compounds catalyzed by Au supported layered double hydroxides: Influencing factors, kinetics and mechanism.

In this paper, factors of initial concentration, catalyst dosage, irradiation intensity, relative humidity and reaction temperature onto visible light gaseous o-xylene photodegradation by ZnCr layered double hydroxides (ZnCr-LDHs) and Au supported ZnCr-LDHs (Au/ZnCr-LDHs) were investigated. ZnCr-LDHs shows low removal efficiency for o-xylene photodegradation, while Au/ZnCr-LDHs exhibits both excellent photodegradation rate and high TOF values for o-xylene as well as other VOCs including benzene, o-xylene, m-xylene and p-xylene. The kinetic equation and activation energy were calculated for o-xylene photodegradation, which are [Formula: see text] and 21.85 kJ/mol for ZnCr-LDH [Formula: see text] and 12.84 kJ/mol for Au/ZnCr-LDHs. The obvious difference both in kinetic equation and activation energy suggests the reaction mechanism of ZnCr-LDHs and Au/ZnCr-LDHs should be very different. The active species inhabitation experiments show that the major drive of photocatalytic reaction for ZnCr-LDHs is hydroxyl radical, while for Au/ZnCr-LDHs it is the hole and hydroxide radical. It is also proved that the support of Au NPs onto LDHs would result in the transfer of photoexcited electrons from LDHs to Au NPs which results in the enhancement of photocatalytic property as well as photocatalytic mechanism change based on UV-vis, XPS, the contribution of different wavelength ranges of visible light onto photocatalytic efficiency and electrochemical tests.

Orthogonal synthesis of a novel hybrid layered material containing three different zincous components and its photocatalytic property investigation.

A novel hybrid layered material-Schiff Base-Zinc Complexes intercalated ZnCr-LDHs-supported ZnO-was synthesized by one-step coprecipitation method and characterized by XRD, UV-vis DRS, SEM, TEM, BET, ICP-AES and XPS analysis. The influences of the three Zn components (intercalated between the layers, supported on the surface, distributed in the host layers of the layered material) on the crystallinity and the photocatalytic activity of ZnO/ZnCr-SalenZn-LDHs for Rhodamine B (RhB) degradation were studied in detail by orthogonal design. The results showed that the percentage of the three components has a great effect on the structure and photocatalytic performance of ZnO/ZnCr-SalenZn-LDHs. The SalenZn intercalated between the layers and the Zn distributed in the layers of the layered material were the main influencing factors, and the ZnO supported on the surface of the layered material was the secondary influencing factor. The optimum initial molar ratios were SalenZn:Cr = 0.5, Zn:Cr = 3, and ZnO:Cr = 0.75, respectively, and the photocatalytic degradation efficiency of RhB reached 96.9%. In addition, a possible mechanism of photocatalysis was discussed from the perspectives of photogenerated reactive species and photoinduced carries transfer. While, the regeneration of the best photocatalytic material was also investigated in detail.

Ti/ZnO-MxOy composites (M = Al, Cr, Fe, Ce): synthesis, characterization and application as highly efficient photocatalysts for hexachlorobenzene degradation.

A series of novel organic-inorganic nanoscale layered materials were synthesized by intercalating the Ti-containing Schiff base complex into the interlayer of the ZnM layered double hydroxides (LDHs, M = Al, Cr, Fe, Ce). The hybrid material was further calcined to make metal oxide composites with highly dispersed Ti elements (Ti/ZnO-MxOy). The structural characterization and photocatalytic results showed that, after intercalation and calcination, the metal oxide composites with a unique flower-like crystal morphology not only had high specific surface area, uniform pore size distribution and narrow band gap, but also showed extremely high photocatalytic performance for hexachlorobenzene (HCB) degradation. The Ti/ZnO-Cr2O3 composite with the narrowest band gap (2.40 eV) and the highest surface area (227 m(2)) showed the highest photocatalytic performance for HCB (95.5% within 240 min) among the four metal oxide composites. Particularly, it was found that composites derived from layered materials with different supramolecular structure of the host and guest showed different photocatalytic properties. In addition, based on the results from ESR, GC-MS and HPLC-MS, the type and amount of hydroxyl radicals, the decomposition intermediates and the pathway of HCB degradation photocatalyzed by Ti/ZnO-MxOy composites are also discussed in detail.

Photocatalytic degradation of methylene blue with a nanocomposite system: synthesis, photocatalysis and degradation pathways.

Three different composites, including a calcined FeOOH supported ZnAl layered double hydroxide (FeOOH-LDO), a calcined ZnAl layered double hydroxide (ZnAl-LDO) and a calcined ZnFeAl layered double hydroxide (ZnFeAl-LDO), were synthesized via a sol-gel method, and their activity for the visible light photocatalytic degradation of methylene blue (MB) was studied. The composites were characterized by PXRD, SEM, and BET techniques, confirming the formation of highly crystalline structures. The activity performance of MB degradation was in the following order: FeOOH-LDO (∼95%) > ZnFeAl-LDO (∼60%) > ZnAl-LDO (∼23%). In addition, a possible photocatalytic degradation reaction mechanism for MB was also proposed. Moreover, the frontier electron densities on the atoms of MB were calculated, which were in satisfactory agreement with the postulated mechanism.