Simulated Solar Light Irradiation Research Articles

TiO2 encased TaN nanoparticles heterojunction for photocatalytic H2 evolution from aqueous glycerol solution

Steering of photo excitons via interface engineering of semiconductor photocatalysts is key to achieving a stable and efficient photocatalyst for continuous hydrogen production. Among them, the development of binary nanocomposites have several advantages such as larger surface area, effective light harvesting, improved photoexcitons separation for red-ox reactions, and non-corrosive nature has received special attention. In this work, nanocomposite of metallic TaN nanoparticles attached with TiO2 layer was successfully synthesized using hydrothermal method. HR-TEM analysis revealed the formation of metallic TaN wrapped with TiO2 with irregular spherical morphology. Electrochemical analysis revealed that Schottky barrier is formed at the interface between TaN and TiO2, with the barrier potential also being dependent on the wrapped layer thickness. However, the hot electrons diffusion through TiO2 energy states can attend the photocatalytic reaction, only when they pass over the Schottky barrier. TaN plays a key role in boosting photocatalytic activity by promoting the separation and transfer of photoexcitons. As the thickness of the TiO2 layer increases, the rate of H2 production initially increases and then decreases. This is consistent with the trend for layer thickness-dependent photocatalytic hydrogen evolution. In addition to catalytic stability, time on stream, recyclability, and parametric analysis aided in optimization of ideal experimental conditions is revealed. Under optimal conditions, the photocatalyst showed an enhanced rate of H2 generation (18.2 mmol h−1. g−1cat) under simulated solar light irradiation.

Enhanced [formula omitted] sites with substitutional defects of [formula omitted] on Zn(O,S) for high-rate hydrogen generation under simulated solar-light irradiation

Carbon-free fuels are required to meet the net-zero emission in 2050 and hydrogen fuel is promising as the future solution. In this work, the hydrogen-evolved Zn(O,S) photocatalyst is improved by doping Li into its lattice with different amounts of LiNO3 precursor. The single phase of Li-doped Zn(O,S) has been confirmed with XRD and TEM analysis. In addition, the electrochemical and optical properties of catalysts are studied with EIS, TPC, DRS, and PL analyses. Li-ZnOS-10 exhibits interesting behaviors with a lower charge transfer resistivity, good photoresponse, and lower PL emission, suggesting it is a promising photocatalyst material. The as-prepared catalysts are tested for hydrogen generation reaction with simulated solar-light illumination. Li-ZnOS-10 catalyst can produce ∼15 mmol/gh and convert 30 ppm nitrobenzene to aniline entirely in 3 h. XPS analysis indicates a low amount of Li dopant in Zn(O,S), implying the formation of LiZn− surface defect that attracts the H+ to longer its lifetime for hydrogenation reaction. Furthermore, the indicated oxygen vacancy sites (VO2+) also play a crucial role in interacting with nitrobenzene and trapping electrons during photoreaction. This work demonstrated improved hydrogen generation reaction and the possible application for green chemical conversion.

Comparative investigation on defect-engineered Bi2S3-xSex for boosting photocatalytic Cr(VI) reduction and in-situ H2O2 generation: Mechanistic and kinetic studies

Heterogeneous photocatalysis has been demonstrated as a highly effective approach in addressing the difficulties encountered by conventional technologies in environmental remediation. Herein, for the first time, a novel hierarchical photocatalyst of selenium-doped Bi2S3 (Bi2S3-xSex) was successfully synthesized through a one-spot hydrothermal route followed by a vacancy engineering process (V-Bi2S3-xSex). The photocatalytic reduction of Cr(VI) and in-situ generation of hydrogen peroxide (H2O2) under simulated solar-light irradiation were performed to evaluate the catalytic activity of the as-prepared samples. The catalytic activity of as-prepared samples was evaluated toward the photocatalytic reduction of Cr(VI) and in-situ generation of H2O2 under simulated solar-light irradiation. Notably, V-Bi2S3-xSex (V-BSSe-5, as optimum sample) exhibited a photo-reduction of Cr(VI) at a rate of 97.04% during 150 min, which was 1.53- and 1.39-fold higher than those of pure Bi2S3 and Bi2Se3, respectively. Interestingly, the V-Bi2S3-xSex photocatalyst not only harvested more incident light in the UV–vis and near-infrared (NIR) regions but also supplied many active sites, improving the promotion of photo-generated charge-carriers, inhibiting charge recombination, and thus enhancing the photocatalytic activity. In addition, V-BSSe-5 showed greater photocatalytic efficiency for H2O2 generation, which was 15.69, 10.07, and 1.79 times higher than those of Bi2S3, Bi2Se3, and BSSe-5, respectively. The charge-carrier migration pathway and possible photocatalytic mechanisms were systematically discussed by assisting the electron spin resonance and ultraviolet photoelectron spectroscopy analyses. The findings of this study demonstrate that doping and defect engineering strategies have the potential to be a significant advancement in the development of visible- and NIR-light responsiveness photocatalysts, thereby providing a solution to current environmental and energy challenges.

Construction of Pd-Co-doped CdS heterojunctions as efficient platforms in photocatalysis.

In this work, we present the structural, optical and photocatalytic properties of CdS semiconducting nanostructures, doped with palladium- and cobalt-based species. XRD analysis, corroborated by Raman and XPS, demonstrated the growth of CdS crystallites in the hexagonal structure, whereas solvothermal conversion of neat precursor metal salts resulted in the formation of metallic Pd and cobalt oxide, respectively. Scanning electron microscopy imaging certified the dendritic structure of hybrids, especially in the case where CdS was grown in the presence of either palladium- or cobalt-based nanoparticles. XPS surface analysis revealed that a major fraction of metallic Pd nanoparticles was converted to PdO during the in situ growth of CdS nanoparticles. The oxidation of Pd nanoparticles could be ascribed to chemisorption of oxygen phases onto the metal surface. The presence of cocatalyst nanoparticles resulted in an appreciable shift of the absorption edge of the ternary hybrids by about 50 nm. The optimized hybrid was found to photodegrade Orange G dye almost quantitatively within 2 h, by simulated solar light irradiation. Scavenging experiments revealed that hydroxy radicals were the main transient intermediate, leading to the oxidative degradation of the dye.

WS2–TiO2 hetero-photocatalysts for efficient hydrogen evolution via plasmon-induced resonance energy transfer

Lowering the cost and increasing the efficiency of photocatalysts for hydrogen (H2) evolution remain challenging, especially with eco-friendly materials. With these goals in mind, in this study we adopted tungsten disulfide (WS2) nanosheets, a nonmetallic surface plasmon resonance (SPR) material covering P25 TiO2, for plasmon-induced resonance energy transfer (PIRET) to improve the photocarrier response of H2 evolution. Under simulated solar light irradiation, the optimized 2.4W heterostructure provided a durable and outstanding H2 evolution rate (321 μmol g−1 h−1) that was approximately 55.3 times higher than that of TiO2. Raman spectra revealed the presence of dipole–dipole interactions within the WS2–TiO2 heterostructure, while UV–Vis optical absorption spectra indicated that the WS2 absorption range overlaid the band gap of TiO2. Under irradiation with light, the SPR of the WS2 nanosheets underwent near-field dipole-dipole coupling with the excitons of TiO2 to increase the number of excitons and inhibit charge recombination. This study suggests the possibility of using nonmetallic SPR materials for efficient solar energy conversion.

Photocatalytic properties of ZnFe-mixed oxides synthesized via a simple route for water remediation

Abstract ZnFe photocatalysts have been increasingly investigated for water remediation due to the high demands in this field, such as activity, toxicity, cost, and stability. The presented study was focused on the simple, safe, non-toxic, and eco-friendly synthesis and characterization of ZnFe-mixed metal oxides in correlation with their functional properties. Photocatalytic performance of these materials was evaluated by rhodamine B photodegradation under simulated solar light irradiation. The synthesized mixed oxides contained hexagonal wurtzite ZnO as the predominant phase, whereas, after thermal treatment, the formation of the spinel-structured ZnFe2O4 phase was observed. The photocatalysts with the additional spinel phase and thermally treated at 300°C and 500°C exhibited superior photocatalytic activity probably due to the highest amount of the ZnFe2O4 spinel phase, favourable mesoporous structure, and an optimal energy band gap of ∼2.30 eV that initiated higher light-harvesting efficiency. The rhodamine B photodegradation followed zero-order kinetics, indicating complete coverage of active sites by the pollutant substrate. Additionally, photocatalysts showed the highest efficiency at the natural pH (6.8), being in accordance with green synthesis principles. Simple, green route assembling synthesis method, high photodegradation efficiency, and good reusability make these ZnFe-mixed oxides great candidates for potential application in practical wastewater treatments.

Fabrication of optimal oxygen vacancy amount in P/Ag/Ag2O/Ag3PO4/TiO2 through a green photoreduction process for sustainable H2 evolution under solar light

Defects engineering on photocatalysts such as oxygen vacancies (OVs) is an effective approach for improving photocatalytic hydrogen (H2) evolution efficiency. In this study, OVs modified P/Ag/Ag2O/Ag3PO4/TiO2 (PAgT) composite was successfully fabricated via a photoreduction process by controlling the ratio of PAgT to ethanol (16, 12, 8, 6 and 4 g·L-1) under simulated solar light irradiation for the first time. Characterization methods confirmed the presence of OVs in the modified catalysts. Meanwhile, the OVs amount and their effects on the light absorption ability, charge transfer rate, conduction band and H2 evolution efficiency of the catalysts were also investigated. The results indicated that the optimal OVs amount endowed OVs-PAgT-12 with the strongest light absorption, the fastest electron transfer rate and suitable band gap for H2 evolution, leading to the highest H2 yield (863 μmol·h−1·g−1) under solar light irradiation. Moreover, OVs-PAgT-12 exhibited a superior stability during cyclic experiment, indicating its great potential for practical application. Furthermore, a sustainable H2 evolution process was proposed based on a combination of sustainable bio-ethanol resource, stable OVs-PAgT, abundant solar energy and recyclable methanol. This study would provide new insights into the design of defects modified composite photocatalyst for enhanced solar-to-hydrogen conversion.

Incorporating Mesoporous Anatase TiO2 Spheres to Conductive Carbon Black Filled PVDF Membrane for Self-Cleaning Photo(electro)catalytic Filtration

Polyvinylidene fluoride (PVDF) membranes have been widely used for micro/ultrafiltration. However, their hydrophobicity leads to serious membrane fouling over time during the process of dye decolorization, which limits their practical application. Herein, PVDF, mesoporous TiO2 spheres (MTS, ∼460 nm), and carbon black (CB) are strategically hybridized via a polyvinylpyrrolidone (PVP)-assisted phase inversion method. The fabricated PVDF/CB/TiO2 conductive membrane prepared by optimal low-molecular-weight PVP (10 kDa) shows a highly porous structure with macro-voids, and MTS are firmly incorporated into the PVDF/CB membrane matrix with a morphologically intact structure, rendering the ternary and conductive membranes with excellent PEC properties. The decolorization rate of 0.50 mg/L methylene blue (MB) reaches 98.6% under the condition of 1.0 V bias potential and simulated solar light irradiation in a continuous cross-flow filtration process. The •O2– and •OH radicals and photogenerated holes (h+) are mainly responsible for MB decolorization in the PEC system. Our work provided a sustainable and efficient method for dye decolorization by combining the PEC system and membrane technology.

Triptycene-Based Polymer-Incorporated CdxZn1–xS Nanorod with Enhanced Interfacial Charge Transfer for Stable Photocatalytic Hydrogen Production in Seawater

Solar-driven hydrogen (H2) generation from seawater exhibits great economic value in addressing the urgent energy shortage yet faces challenges from the severe salt-deactivation effect, which could result in the consumption of photoinduced charges and decomposition of catalysts. Herein, a triptycene-based polymer was coated on the surface of a CdxZn1-xS nanorod to form a core-shell heterojunction (TCP@CZS) by using the in situ Suzuki reaction for photocatalytic H2 production from water/seawater splitting. The introduction of TCP can provide a large surface area, enrich the active site, and boost charge transfer for the proton reduction reaction. Benefiting from it, optimal TCP@CZS indicated a H2 evolution rate of 93.88 mmol h-1 g-1 with Na2S/Na2SO3 in natural seawater under simulated solar light irradiation, which was 2.2 and 1.1 times higher than that of pure Cd0.6Zn0.4S and that in pure water, respectively. Besides, the apparent quantum efficiency (AQE) of TCP@CZS-3 under 420 nm light irradiation was 22.6% in seawater. This work highlights the feasibility of the triptycene-based porous organic polymer as an efficient catalyst for solar energy conversion in seawater.

Superlattice Nanofilm on a Touchscreen for Photoexcited Bacteria and Virus Killing by Tuning Electronic Defects in the Heterointerface.

Currently, the global COVID-19 pandemic has significantly increased the public attention toward the spread of pathogenic viruses and bacteria on various high-frequency touch surfaces. Developing a self-disinfecting coating on a touchscreen is an urgent and meaningful task. Superlattice materials are among the most promising photocatalysts owing to their efficient charge transfer in abundant heterointerfaces. However, excess electronic defects at the heterointerfaces result in the loss of substantial amounts of photogenerated charge carrier. In this study, a ZnOFe2 O3 superlattice nanofilm is designed via atomic layer deposition for photocatalytic bactericidal and virucidal touchscreen. Additionally, electronic defects in the superlattice heterointerface are engineered. Photogenerated electrons and holes will be rapidly separated and transferred into ZnO and Fe2 O3 across the heterointerfaces owing to the formation of ZnO, FeO, and ZnFe covalent bonds at the heterointerfaces, where ZnO and Fe2 O3 function as electronic donors and receptors, respectively. The high generation capacity of reactive oxygen species results in a high antibacterial and antiviral efficacy (>90%) even against drug-resistant bacteria and H1N1 viruses under simulated solar or low-power LED light irradiation. Meanwhile, this superlattice nanofilm on a touchscreen shows excellent light transmission (>90%), abrasion resistance (106 times the round-trip friction), and biocompatibility.

Z-scheme driven photocatalytic activity of CNTs-integrated Bi2S3/WO3 nanohybrid catalysts for highly efficient hydrogen evolution under solar light irradiation

Harvesting solar energy for the production of molecular hydrogen through photocatalytic approach is a clean and sustainable pathway to deal with the energy crisis and pollution. In this connection, direct Z-scheme interfaced noble metal free CNTs integrated Bi2S3-WO3 ternary composite was designed and developed through simple hydrothermal and wet impregnation strategies. This combination was manifested for the first time to tackle the photo-corrosion of Bi2S3 through Z-scheme heterojunction formation, and its effective contribution in the mitigation of charge carrier recombination was investigated. 9 wt% WO3 loaded Bi2S3 (WB-9) delivered a notable H2 production rate of 4.85 mmol.h−1.g-1cat over 5 vol% glycerol as a sacrificial reagent under simulated solar light irradiation. This enhancement was six folds higher than the pristine Bi2S3 photocatalytic activity. To enhance the reduction half-reaction further, electron mobility was regulated with CNT integration, which not only triggers the successive transport of electrons through its tubular channel, but also facilitate an excellent reduction co-catalyst to support rapid reduction of protons to form H2 molecules. Upon optimization of CNTs loading, 1 wt% CNTs loaded WB-9 (CWB-4) produced two-folds higher H2 production rates than WB-9, which is about 9.91 mmol.h−1. g−1cat. The observed efficiency, stability, and recyclability of CWB-4 attributed to the effective utilization of generated charge carriers across the system and suppressed photo-corrosion of Bi2S3 through the Z-scheme interface.

Integration between CuMOF and g-C3N4 for effective suppressing charge recombination in photocatalytic peroxymonosulfate activation

In this work, CuMOF and graphite phase carbon nitride (g-C3N4) composite was synthesized, and tetracycline hydrochloride (TC) in water was degraded under simulated solar light irradiation with the assistance of peroxymonosulfate (PMS). The prepared g-C3N4/CuMOF samples were characterized by XRD, FT-IR, SEM, TEM and XPS. It is found that the introduction of CuMOF into g-C3N4 was not only beneficial to the charge separation of g-C3N4, but also greatly accelerated the activation of PMS. Through the initial pH value, PMS concentration, catalyst concentration, catalyst repeated use and other factors, the degradation performance of g-C3N4/CuMOF was studied. The photocatalytic experiment results showed that in the presence of PMS, the degradation rate of TC reached 90 % within 30 min. In addition, the reaction mechanism of the g-C3N4/CuMOF/PMS system was studied by using scavenging experiments and electron spin resonance (ESR) technology. This work provides a promising way for the rational design of high-performance and low-cost photocatalysts for environmental remediation.

Platinum quantum dots-decorated MXene-derived titanium dioxide nanowire/Ti3C2 heterostructure for use in solar-driven gas-phase carbon dioxide reduction to yield value-added fuels

Solar-driven photocatalytic CO2 reduction to produce valuable chemicals and fuels offers an attractive strategy in alleviating the energy crisis. Pt quantum dots (PtQDs) with TiO2 nanowire (TiO2NW)/Ti3C2 MXene heterostructures (Pt-TiO2NW/Ti3C2) with tight interfacial contacts between the various components were prepared at room temperature via oxidation reactions. The incorporated PtQDs played crucial roles as electron conduction bridges supported by the cocatalyst effect, effectively enhancing the separation efficiencies of photoinduced electron/hole pairs and improving CO2 reduction under simulated solar light irradiation. The Pt-TiO2NW/Ti3C2 heterostructures exhibited remarkable carbon monoxide (CO) and methane (CH4) production at respective rates of 38.14 and 36.15 μmol g−1 after 10 h of simulated solar light irradiation, an apparent quantum yield of 1.68%, and 79.2% selectivity for CH4. The photocatalytic activities of the Pt-TiO2NW/Ti3C2 heterostructures for CO2 reduction were significantly enhanced compared to those of TiO2NW/Ti3C2 and the single-component photocatalysts, and they exhibited remarkable stabilities even after five cycles. In addition, the densities of states and electronic characteristics of Ti3C2 MXene and Pt-TiO2NW/Ti3C2 were studied using density functional theory, and a synergistic mechanism of the improvement in CO2 photoreduction is proposed.

Multifunctional TiO2/MIL-100(Fe) to conduct adsorption, photocatalytic, and heterogeneous photo-Fenton reactions for removing organic dyes

BackgroundSince TiO2 photocatalysts were only ultraviolet-light-responsive and homogeneous photo-Fenton had some drawbacks in generating iron sludge, multifunctional TiO2/MIL-100(Fe) composites were synthesized to remove organic dyes under simulated solar light irradiation. MethodsCommercial TiO2 and MIL-100(Fe) precursors were mixed in one pot using a modified reflux method in 12 h, 18 h, and 24 h to fabricate TiO2/MIL-100(Fe) with different weight ratios of the TiO2 and Fe(NO3)2 precursors, including 0.07, 0.15, and 0.30. MIL-100(Fe) was used to efficiently distribute TiO2 and adsorb dyes due to its high specific surface area. Besides, TiO2/MIL-100(Fe) composites could absorb visible light to conduct photocatalytic and heterogeneous photo-Fenton reactions simultaneously. Significant findingsFor the TiO2/MIL-100(Fe) composites (TF15-18), the individual kinetics analysis of removing organic dyes, including dark adsorption and light reaction, belonged to the pseudo-second-order model with the rate constants of 1.682 and 7.702 g·mg−1·min−1, respectively. The completed dye removal was achieved under 90 min dark adsorption and 180 min light reaction under the best conditions of pH=3.5 and 40 μL H2O2 addition in 150 mL MB solution.

Plasmonic silver nanoparticle-deposited n-Bi2S3/p-MnOS diode-type catalyst for enhanced photocatalytic nitrogen fixation: Introducing the defective p-MnOS

Photocatalytic nitrogen reduction reaction (PNRR) is clean and sustainable, considered an ideal synthesis technology for ammonia (NH3). In this study, we in situ developed the n-Bi2S3 nanorod/p-MnOS cubic composite catalyst for the first time using a one-step hydrothermal method, as MnOS, listed in the X-ray diffraction standard data file as an uncharacterized compound, has not been reported since 1965. Then, using a photodeposition technique, Ag nanoparticles (NPs) were added to the surface of the Bi2S3/MnOS to enhance PNRR via the surface plasmon resonance. After different characterization techniques for evaluation, Ag-Bi2S3/MnOS is found to be highly effective in the spatial separation of photogenerated electron-hole pairs due to the charge transfer at the composite interface. Photodeposited Ag is applied as an electron trapper to enhance the spatial separation of charge carriers. Based on their ability to reduce nitrogen under simulated solar light irradiation, the PNRR activities of Bi2S3, MnOS, Bi2S3/MnOS, and 0.5 to 2 % Ag-Bi2S3/MnOS were evaluated. After two hours, the PNRR activity of 1 % Ag-Bi2S3/MnOS produced ammonia 5.9 mmol/g, double the amount of Bi2S3/MnOS composite and approximately 5 times the amounts of Bi2S3 and MnOS materials. PNRR enhancement involves the internal static electron field created at the n-type Bi2S3/p-type MnOS interface and the improved electron conductivity with the photodeposition of Ag NPs, to speed up the reaction of reactive species. The importance of solid solution engineering in material design is demonstrated in this work.

Solar Light-Induced Photocatalytic Degradation of Sulfamethoxazole by Cobalt Phosphide-Promoted Bismuth Vanadate

The pursuit of low-cost, high-efficiency co-catalysts that are free of noble metals has become an area of considerable interest in the field of photocatalysis over the past few years. In this work, a series of cobalt phosphide (CoP 0.125–1.00 wt.%)-promoted bismuth vanadate (BiVO4) photocatalysts was synthesized and physicochemical characterized by means of X-Ray diffraction, nitrogen isotherm absorption diffuse-reflectance spectroscopy, and high-resolution transmission electron microscopy. The efficiency of the as prepared photocatalytic materials was investigated for sulfamethoxazole (SMX) destruction in ultrapure water under simulated solar light irradiation. Results showed that the deposition of small amounts (0.50 wt.%) of CoP on BiVO4 enhances SMX degradation. Moreover, SMX removal increased by increasing 0.50 CoP/BiVO4 loading (up to 1 g/L) and decreasing SMX loading (1000–250 μg/L). Further tests were carried out in real and synthetic matrices, such as wastewater secondary effluent and bottled water, revealing the existence of hindering effects on SMX removal. The efficiency of 0.50 CoP/BiVO4 photocatalyst was further investigated in a pilot plant configuration where the examined system was able to remove >99% of 300 μg/L SMX in deionized water utilizing 80 kJ/L of solar irradiation.

Titania nanorods array homojunction with sub-stoichiometric TiO2 for enhanced methylene blue photodegradation

TiO2 thin films are known to promote photodegradation of dyes and pollutants in water solution via heterogeneous photocatalysis. This ability is guided by the photoexcitation through photons having energies above the band gap. To improve photocatalytic activity, nanostructures with high surface area can be applied, which can ease molecular adsorption/desorption mechanisms, enhance electronic transfer properties and lower excitation energy. For this purpose, square cross-section TiO2 vertically aligned nanorod (TNR) array configuration has been chosen as a semiconductor substrate. On top of it, a thin layer of sub-stoichiometric TiO2−x has been deposited, aiming at inducing a vacancy doped homojunction between two different oxygen rich/deficient TiO2 layers, possibly leading to lower band gap and enhanced photochemical activity. In principle, promotion of electron and holes separation and suppression of charge recombination could occur. Vertically aligned TNRs have been deposited through a hydrothermal growth in acidic conditions on a pre-seeded glass conducting substrate, optimizing the seeding process through spin coating. Sub-stoichiometric TiO2−x layer (50 nm nominal thickness) has been deposited on top of TNRs via radiofrequency magnetron sputtering at three different stoichiometries, tuning the oxygen partial pressure in sputtering argon atmosphere at 10 %, 15 % and 20 %, respectively. Photocatalytic activity has been investigated in the photodegradation of an aqueous solution of methylene blue, both under UV and simulated solar light irradiation at room temperature and atmospheric pressure, resulting in the degradation of methylene blue target molecule up to 99 % under UV and 85 % under simulated solar irradiation after 6 h. These promising achievements unlock new environmental applications for enhanced dye degradation industrial processes.

Bi12TiO20-TiO2 S-scheme heterojunction for improved photocatalytic NO removal: Experimental and DFT insights

The fabrication of step-scheme (S-scheme) photocatalysts with superior redox ability for air purification is very important but remains a challenge. In this study, an S-scheme Bi12TiO20-TiO2 heterojunction is prepared for photocatalytic NO removal. The optimized Bi12TiO20-TiO2 heterojunction shows higher NO removal efficiency (42.6 %) than that of pristine Bi12TiO20 (8.7 %) and TiO2 (21.4 %) under simulated solar light irradiation. The enhanced photocatalytic activity can be attributed to the efficient separation and transfer efficiency of photoinduced electrons-hole pairs, enhanced redox ability, and increased NO adsorption capacity induced by S-scheme heterojunction between Bi12TiO20 and TiO2. The S-scheme charge transfer mechanism on Bi12TiO20-TiO2 heterojunction is proposed based on characterizations and theoretical calculations. The NO conversion process is investigated using in-situ Fourier transform infrared spectroscopy (in-situ FTIR). This study provides new insights for exploring highly efficient photocatalysts for NO removal.

ZnO with engineered surface defects as a competent photocatalyst for CO2 photoreduction into valuable fuels under simulated solar light irradiation

Photocatalysis is one of the eco-friendly methods in greenhouse gases abatement by utilizing renewable resources such as sunlight. This study examined defective ZnO nanoparticles that serve as carbon dioxide (CO2) adsorption and activation sites in photocatalytic reactions. The defective ZnO nanoparticles were synthesized via a facile precipitation-hydrothermal method by only controlling the concentration of NaOH as the precipitating agent. The rough surface of ZnO were formed due to the heating treatment, where it conveniently removed the attached inorganic molecules on ZnO surfaces. The roughness surface of ZnO was observed by using Transmission Electron Microscopy (TEM) analysis, in which the pores with bright spot can be observed. Additionally, the defects originating from oxygen vacancies (VO), zinc interstitials (Zni) and carbonates groups (CO32−) was successfully optimized over variation of NaOH concentrations proven by Photoluminescence (PL) and X-Ray Photoelectron Spectroscopy (XPS) analysis. Here, 1 : 4 ZnO exhibited the highest CH4 yield (1.3 ×10-1 µmol) and 3-fold production than commercial ZnO (4.8 × 10-2 µmol). The reusability of 1 : 4 ZnO was demonstrated by conducting 4 cycles of stability test, which revealed a robust photocatalyst of 7.7% performance reduction after 4th cycle. A schematic mechanism pertaining to the novel defective ZnO nanoparticles in CO2 photoreduction to valuable fuels was proposed in this study, which undoubtedly will contribute a positive effect to industry’s long-term sustainability.

Construction adsorption and photocatalytic interfaces between C, O co-doped BN and Pd-Cu alloy nanocrystals for effective conversion of CO2 to CO

Photocatalytic reduction of carbon dioxide (CO2) into fuels is an auspicious route to alleviate the energy and environmental crisis brought by the continuous depletion of fossil fuels. The CO2 adsorption state on the surface of photocatalytic materials plays a significant role in its efficient conversion. The limited CO2 adsorption capacity of conventional semiconductor materials inhibit their photocatalytic performances. In this work, a bifunctional material for CO2 capture and photocatalytic reduction was fabricated by introducing palladium (Pd)-copper (Cu) alloy nanocrystals onto the surface of carbon, oxygen co-doped boron nitride (BN). The elemental doped BN with abundant ultra-micropores had high CO2 capture ability, and CO2 was adsorbed in the form of bicarbonate on its surface with the presence of water vapor. The Pd/Cu molar ratio had great impact on the grain size of Pd-Cu alloy and their distribution on BN. The CO2 molecules tended to be converted to carbon monoxide (CO) at interfaces of BN and Pd-Cu alloys due to their bidirectional interactions to the adsorbed intermediate species while methane (CH4) evolution might occur on the surface of Pd-Cu alloys. Owing to the uniform distribution of smaller Pd-Cu nanocrystals on BN, more effective interfaces were created in the Pd5Cu1/BN sample and it gave a CO production rate of 7.74 μmolg−1h−1 under simulated solar light irradiation, higher than the other PdCu/BN composites. This work can pave a new way for constructing effective bifunctional photo-catalysts with high selectivity to convert CO2 to CO.