Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Plasmon-Driven Photochemical Reduction Reaction on Silver Nanostructures for Green Fabrication of Superhydrophobic Surface

Green fabrication of superhydrophobic surface by water-based processing is still challenging, because introduction of the substances with hydrophilic moieties compromises its superhydrophobicity. Herein, a plasmon-driven photochemical reduction reaction under ultraviolet light (UVA) irradiation is first discovered and is applied to deoxygenation of hydrophilic organic adsorbates on rough nano-Ag coating for the formation of stable superhydrophobic surface. A nano-Ag coating with strong localized surface plasmon resonance in the UVA region is prepared by a water-based silver mirror reaction and results in a unique chemical reduction reaction on its surface. Consequently, the low residual hydrophilic functionalities and the formed cross-linked structure of the adsorbate on Ag nanoparticles (NPs) enables the coating to exhibit stable superhydrophobicity against to both air and water. The superhydrophobic Ag NP-coated sandpaper can also be used as a surface-enhanced Raman scattering (SERS) substrate to concentrate aqueous analytes for trace detection.

Inductive Effect of Lewis Acidic Dopants on the Band Levels of Perovskite for a Photocatalytic Reaction

Band-edge modulation of halide perovskites as photoabsorbers plays significant roles in the application of photovoltaic and photochemical systems. Here, Lewis acidity of dopants (M) as the new descriptor of engineering the band-edge position of the perovskite is investigated in the gradiently doped perovskite along the core-to-surface (CsPbBr₃-CsPb_1-xM_xBr₃). Reducing M-bromide bond strength with an increase in hardness of acidic M increases the electron ability of basic Br, thus strengthening the Pb-Br orbital coupling in M-Pb-Br, noted as the inductive effect of dopants. Especially, the highly hard Lewis acidic Mg localized in the outer position of the perovskite induces the increase of work function and then shifts band edge upward along the core-to-surface of the perovskite. Thus, charge separation driven by the dopant-induced internal electric field induces the slow annihilation of the excited holes, improving the slow aromatic C_sp³-H dissociation in the photocatalytic oxidation process by ∼211% (491.39 μmol g^-1 h^-1) enhancements, compared with undoped nanocrystals.

Precise real-time quantification for photocatalytic reaction: integration of the sensitivein-situSERS sensor and high-efficiency photocatalyst

Recently,in-situsurface-enhanced Raman spectroscopy (SERS) is gradually becoming an important method for monitoring photocatalytic reaction processes, in which the quantification potential is a vital factor in determining whether this technology can be truly applied in the future. In order to improve the quantification performance ofin-situSERS and explore a precise operando Raman detection for photocatalytic reactions, an architecture of heterostructural Cu₂O/ZnO/Ag nano round brush has been designed and discussed in this work. This structure is an integration of sensitivein-situSERS sensor and high-efficiency photocatalyst, realizing real-time monitoring of photocatalytic reaction in a wide concentration range from 20 to 3 mg l^-1. The coefficient of determination between different detection methods is beyond 0.86 in this range, implying the high-precise quantification of this platform. Comprehensive analysis on structure effect, SERS performance, photocatalytic property, electric filed characteristic, etc were all systematically made and discussed in detail for this platform. This work presents a precise preliminar real-time photocatalytic monitoring usingin-situSERS detection, which is a new attempt and also meaningful reference for otherin-situanalytical technology.

The Effectiveness of Liquid PUD-TiO2 Photocatalyst on Asphalt Pavement

Harmful nitrogen oxides (NO_X) are produced by vehicles, factories, mines, and power plants. In fact, over one million tons of NO_X are emitted into the atmosphere every year, making it the most prevalent air pollutant. Approximately 45% of the emitted NO_X in Korea is associated with the transportation sector. In this paper, the application of a new TiO₂ photocatalyst on the asphalt roads to remove combustion-produced NO_X was studied. In an effort to overcome the known constructability, adhesion, cost, and dispersion problems associated with TiO₂ photocatalysts, the liquid polyurethane (PUD) was added with TiO₂ to form a mixture later known as liquid PUD-TiO₂. Laboratory and field tests were conducted to determine the optimum amount of photocatalyst to be used and the performance of asphalt pavement coated with PUD-TiO₂ in terms of indirect tensile strength, water susceptibility, and rutting resistance. Additionally, the performance of PUD-TiO₂ under different humidity, wind speed, and temperature conditions was also evaluated. The results showed that the application of PUD-TiO₂ photocatalyst on the asphalt pavements road reduces the NO_X available on the surface of the road. The PUD-TiO₂ also was found to have no effects on the performance of asphalt pavement. Meanwhile, under different weather conditions, the reaction between the photocatalyst and NO_X is mainly affected by the humidity.

Miniaturized Portable Total Phosphorus Analysis Device Based on Photocatalytic Reaction for the Prevention of Eutrophication

Phosphorus (P) is one of the most important elements in the aquatic ecosystem, but its overuse causes eutrophication, which is a serious issue worldwide. In this study, we developed a miniaturized portable total phosphorus (TP) analysis device by integrating a TP sensor with a photocatalyst to pretreat analyte and optical components (LED and photodetector) to measure the absorbance of the blue-colored analyte for real-time TP monitoring and prevention of eutrophication. The size of the miniaturized portable TP analysis device is about 10.5 cm × 9.5 cm × 8 cm. Analyte-containing phosphorus was pretreated and colored blue by colorizing agent as a function of the phosphorus concentration. Absorbance of the blue-colored analyte was estimated by the LED and the photodetector such that the phosphorus concentration was quantitatively measured. This device can obtain a wide linear response range from 0.5 mg/L to 2.0 mg/L (R2 = 0.97381), and its performance can be improved by increasing the intensity of the UV light emitted from the LED array. Consequently, the performance of this miniaturized portable TP analysis device was found to be similar to that of a conventional TP analysis system; thus, it can be used in automated in situ TP analysis.

Understanding and Improving Photocatalytic Activity of Pd-Loaded BiVO4 Microspheres: Application to Visible Light-Induced Suzuki-Miyaura Coupling Reaction

The effective utilization of visible light is required for exploiting photocatalytic reactions in indoor and outdoor environments. In this study, Pd-supported BiVO₄ microspheres (Pd-BiVO₄) were prepared for visible light-induced photocatalytic reactions. Under irradiation with a white light-emitting diode, the obtained Pd-BiVO₄ composite exhibited considerably improved catalytic activity for the decomposition of an organic dye compared with other BiVO₄ catalysts. The Pd-BiVO₄ composite was also effective for catalytic organic transformation via the visible light-induced Suzuki-Miyaura coupling reaction. The photogenerated electrons in the conduction band of BiVO₄ flowed to the Pd nanoparticles and amplified cross-coupling reaction. The influence of the crystal structure and grain size of BiVO₄ and the role of the deposited Pd nanoparticles were fully investigated to elucidate the visible light activity of the catalyst. This system highlights the possibility of an indoor light source with low energy density for sustainable organic transformations.

Synthesis and Performance of TiO2/Fly Ash Cenospheres as a Catalytic Film in a Novel Type of Periodic Air-Sparged Photocatalytic Reactor

The results of a photocatalytic process performed in a new type of inclined, three-phase fluidised bed reactor with a periodic photocatalyst film are presented. These phases were fly ash cenospheres coated with TiO2, an aqueous solution of methylene blue and an air stream passing from the bottom of the photoreactor. The cenospheres have a density lower than water and could thus form a catalytic film on a top irradiated window. The formed surface film is stable but is easy to break and be reproduced in a cyclic air-sparged process. Mixing was performed in either a cyclic or a continuous manner. From an operational point of view, the best variant of mixing was a 10 s air-sparge/10 s break with a 50% duty cycle, because it provided the same discolouration efficiency and reduced energy demand by 50% in comparison with the continuous mixing. Due to film formation, the proposed catalytic reactor enables a substantial reduction in the energy required for mixing while maintaining the desired degree of discolouration.

[Application of Fenton-like Photocatalysts Based on Defect Reconstruction in Degradation of Dye Wastewater]

In recent years, improving the performance of catalysts through defect modulation has attracted extensive attention. However, the impact of defect rearrangement on Fenton-like photocatalytic reactions has not been studied. In this study, Fe-containing polyoxometalate molecules were grafted onto the surface of defective TiO₂.The influence of oxygen vacancy formation and the defect arrangement process on the catalytic activity was investigated. The results indicated that the calcination of cyanamide modified defective TiO₂ is beneficial for the spatial reconstruction of oxygen vacancies generated by H₂ atmosphere treatment. With rearranged structural defects, photo-generated electrons were prone to transfer from the surface of P25 to Fe-POM nanoparticles. Due to the enhanced charge separation in TiO₂ and the increased reactive sites on the Fenton-like reagent, Fenton-like photocatalysts with rearranged defects showed a 13-fold increase in catalytic activity during the degradation of dye molecules.

Photocatalytic CO2 Reduction Using Various Heteroleptic Diimine-Diphosphine Cu(I) Complexes as Photosensitizers

The development of efficient redox-photosensitizers based on the earth-abundant metal ions as an alternative toward noble- and/or rare-metal based photosensitizers is very desirable. In recent years, heteroleptic diimine-diphosphine Cu(I) complexes have been well investigated as one of the most remarkable candidates because of their great potentials as efficient photosensitizers. Here, we investigated the effects of the structure of the diphosphine ligands on the photosensitizing abilities using a series of Cu(I) complexes bearing 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmpp) and various diphosphine ligands in order to explore the suitable structure for the photosensitizing reactions. The number of methylene chains between the two phosphorous atoms in the diphosphine ligands was systematically changed from two to four, and the relationship between the length of the carbon chains and the photosensitizing abilities were investigated by conducting photocatalytic CO₂ reduction with the Cu(I) complexes as photosensitizers. Turnover frequencies of the CO₂ reduction drastically increased with increasing the length of the carbon chains. The systematic study herein reported suggests that the large P-Cu-P angles should be one of the most important factors for enhancing the photosensitizing abilities.

Preparation of a New Type of Black TiO2 under a Vacuum Atmosphere for Sunlight Photocatalysis

Black TiO₂ as a solar-driven photocatalyst has attracted enormous attention from scientists and engineers in water and wastewater treatment field. Most of the methods used for the preparation of black TiO₂ are thermal treatment under a hydrogen atmosphere. Nevertheless, it is well known that working with hydrogen is not safe and needs special maintenance. Here, for the first time, we prepared black TiO₂ by sintering P25 pellets at different temperatures (500-800 °C) under a vacuum atmosphere that showed the same performance with the prepared black TiO₂ under a hydrogen atmosphere. The samples were characterized by X-ray diffraction, Raman spectra field emission scanning electron microscopy, transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and ultraviolet-visible deep resistivity sounding techniques. The differences between the formation of oxygen vacancy density and color turning in sintered powder and pellet were also studied. The results showed that the color of the P25 powder became darker after sintering but not completely turning to black, whereas the P25 pellets completely turned black after sintering. The resultant black TiO₂ was used for the photocatalytic degradation of the acetaminophen (ACE) in aqueous solution under AM 1.5G solar light illumination; it was found that the P25 pellet sintered in 500 °C had the highest photocatalytic performance for ACE degradation under AM 1.5G solar light illumination. The photocatalytic activity of prepared black TiO₂ under vacuum and hydrogen atmospheres was also compared together; the results showed that photocatalytic activities of both samples were so close together. The existence of the oxygen vacancy after 6 months and long and short-term stability (by application for photocatalytic degradation of ACE in an aqueous solution) of the black TiO₂ pellets was also studied; the results showed that the TiO₂ pellets in aqueous phase had acceptable stability.

Raman Spectroscopy, Photocatalytic Degradation, and Stabilization of Atomically Thin Chromium Tri-iodide

As a 2D ferromagnetic semiconductor with magnetic ordering, atomically thin chromium tri-iodide is the latest addition to the family of two-dimensional (2D) materials. However, realistic exploration of CrI₃-based devices and heterostructures is challenging due to its extreme instability under ambient conditions. Here, we present Raman characterization of CrI₃ and demonstrate that the main degradation pathway of CrI₃ is the photocatalytic substitution of iodine by water. While simple encapsulation by Al₂O₃, PMMA, and hexagonal BN (hBN) only leads to modest reduction in degradation rate, minimizing light exposure markedly improves stability, and CrI₃ sheets sandwiched between hBN layers are air-stable for >10 days. By monitoring the transfer characteristics of the CrI₃/graphene heterostructure over the course of degradation, we show that the aquachromium solution hole-dopes graphene.

Improvement in Electrical Characteristics of Eco-friendly Indium Zinc Oxide Thin-Film Transistors by Photocatalytic Reaction

Eco-friendly solution-processed oxide thin-film transistors (TFTs) were fabricated through photocatalytic reaction of titanium dioxide (PRT). The titanium dioxide (TiO₂) surface reacts with H₂O under ultraviolet (UV) light irradiation and generates hydroxyl radicals (OH•). These hydroxyl radicals accelerate the decomposition of large organic compounds such as 2-methoxyethanol (2ME; one of the representative solvents for solution-processed metal oxides), creating smaller organic molecular structures compared with 2ME. The decomposed small organic materials have low molar masses and low boiling points, which help improving electrical properties via diminishing defect sites in oxide channel layers and fabricating low-temperature solution-processed oxide TFTs. As a result, the field-effect mobility improved from 4.29 to 10.24 cm²/V·s for IGZO TFTs and from 2.78 to 7.82 cm²/V·s for IZO TFTs, and the V_th shift caused by positive bias stress and negative bias illumination stress over 1000 s under 5700 lux decreased from 6.2 to 2.9 V and from 15.3 to 2.8 V, respectively. In theory, TiO₂ has a permanent photocatalytic reaction; as such, hydroxyl radicals are generated continuously under UV irradiation, improving the electrical characteristics of solution-processed IZO TFTs even after four iterations of TiO₂ recycling in this study. Thus, the PRT method provides an eco-friendly approach for high-performance solution-processed oxide TFTs.

A Gallium Oxide-Graphene Oxide Hybrid Composite for Enhanced Photocatalytic Reaction

Hybrid composites (HCs) made up of gallium oxide (GaO) and graphene oxide (GO) were investigated with the intent of enhancing a photocatalytic reaction under ultraviolet (UV) radiation. The material properties of both GaO and GO were preserved, even after the formation of the HCs. The incorporation of the GO into the GaO significantly enhanced the photocatalytic reaction, as indicated by the amount of methylene blue (MB) degradation. The improvements in the reaction were discussed in terms of increased surface area and the retarded recombination of generated charged carriers.

Complexes in the photocatalytic reaction of CO(2) and H(2)O: theoretical studies

Complexes (H₂O/CO₂, e–(H₂O/CO₂) and h⁺–(H₂O/CO₂)) in the reaction system of CO₂ photoreduction with H₂O were researched by B3LYP and MP2 methods along with natural bond orbital (NBO) analysis. Geometries of these complexes were optimized and frequencies analysis performed. H₂O/CO₂ captured photo-induced electron and hole produced e–(H₂O/CO₂) and h⁺–(H₂O/CO₂), respectively. The results revealed that CO₂ and H₂O molecules could be activated by the photo-induced electrons and holes, and each of these complexes possessed two isomers. Due to the effect of photo-induced electrons, the bond length of C=O and H-O were lengthened, while H-O bonds were shortened, influenced by holes. The infrared (IR) adsorption frequencies of these complexes were different from that of CO₂ and H₂O, which might be attributed to the synergistic effect and which could not be captured experimentally.