Photocatalytic Reaction Mechanism Research Articles

Accelerating carrier separation to boost the photocatalytic CO2 reduction performance of ternary heterojunction Ag-Ti3C2Tx/ZnO catalysts.

Developing low-cost and efficient photocatalyst/co-catalyst systems that promote CO2 reduction remains a challenge. In this work, Ag-Ti3C2Tx composites were made using a self-reduction technique, and unique Ag-Ti3C2Tx/ZnO ternary heterojunction structure photocatalysts were created using an electrostatic self-assembly process. The photocatalyst's close-contact heterogeneous interface increases photogenerated carrier migration efficiency. The combination of Ti3C2Tx and Ag improves the adsorption active sites and reaction centers for ZnO, making it a key site for CO2 adsorption and activation. The best photocatalysts had CO and CH4 reduction efficiencies of 11.985 and 0.768 μmol g-1 h-1, respectively. The CO2 conversion was 3.35 times better than that of pure ZnO, which demonstrated remarkable stability even after four cycle trials with no sacrificial agent. Furthermore, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) and valence band spectroscopy were utilized to propose the photocatalytic reaction mechanism and electron transfer channels of the Ag-Ti3C2Tx/ZnO system, confirming that CHO* and CO* are the important intermediates in the generation of CH4 and CO. This study introduces a novel method for the development of new and efficient photocatalysts and reveals that Ti3C2Tx MXene is a viable co-catalyst for applications.

Self-assembled composite heterojunction material PDIsm/BiOCOOH promotes photocatalytic degradation of levofloxacin

A broad-spectrum responsive organic-inorganic heterojunction was synthesized by in-situ self-assembled perylene diimide (PDIsm) through π-π stacking onto the surface of flower-like BiOCOOH. The PDIsm/BiOCOOH with different compositions exhibited enhanced photocatalytic degradation of levofloxacin under visible light irradiation. Among them, 10% PDIsm/BiOCOOH had the best photocatalytic activity, which was 4.6 and 14.1 times higher than pure PDIsm and BiOCOOH, respectively. The enhancement of photocatalytic activity was mainly attributed to the introduction of PDIsm which significantly improved the light absorption in almost the whole visible light range. Besides, the formed heterojunctions facilitate the separation and transfer of photogenerated charge carriers. In addition, after five cycles of degradation, the degradation rate of the PDIsm/BiOCOOH composite for levofloxacin hydrochloride remained above 75%, indicating its good photocatalytic activity and stability. Furthermore, free radical capture experiments and electron spin resonance experiments verify that •O2‾ and h+ were the active species generated in the photocatalytic process. Combining the experimental results of high-performance liquid chromatography-mass spectrometry, a possible photocatalytic reaction mechanism was proposed. This work provides a way to prepare an efficient organic-inorganic photocatalyst, which can potentially be utilized in environmental remediation under visible light.

Photo-Generated Charge Carrier Dynamics in Metal Oxide Photocatalysts

Solar water splitting is one of the most attractive energy carrier generation processes to utilize solar energy. Light generated hydrogen is a clean energy carrier, since their consumption for energy generation produces only water. Moreover, generated hydrogen can be stored and used whenever required. Hydrogen is mostly used as a feedstock in the chemical and petrochemical industries, e.g. production of ammonia, methanol and fertilisers.[1]The photocatalytic solar water splitting process has been studied extensively over the last half century. However, despite the efforts, no ideal photocatalyst has yet been identified to meet three main requirements for commercialisation: (1) low cost, (2) high solar to hydrogen (STH) efficiency and (3) durability. Over the last two decades, considerable efforts have focused on developing visible light active photocatalysts, and some promising photocatalysts with relatively high water splitting efficiency were discovered.[2] In contrast to search of appropriate photocatalyst (nano)materials, mechanisms of photocatalytic water splitting reactions, in particular charge carrier dynamics of photocatalysts, were little studied. Understanding charge carrier dynamics in photocatalysts will certainly provide an opportunity to design high efficiency photocatalysts.In this presentation, we will show dynamics of photo-generated charge carries in metal oxide photocatalyst by employing a series of transient absorption spectroscopies covering from 150 fs to 100 s over UV-VIS-NIR wavelength ranges.[2] Correlation of the charge carrier dynamics with photocatalysis reactions will be discussed.This work was partly supported by ARC DP fund (DP180103815) and ARC LIEF funds (LE170100235 and LE200100051), Australia, and the Collaborative Research Program of Institute for Chemical Research, Kyoto University (grant number 2023-45 and 2022-99), Japan. We also acknowledge supports from School of Engineering, RMIT University, and Forefront Research Center, Faculty of Science, Osaka University.

ZIF-8 incorporated CeO2-CdS quantum dots @ 2D g-C3N4 nanosheets as a staggered type II heterojunction for decolouration of a set of dyes

Dye toxins, emitted by industries, pose a significant threat to living beings and aquatic life by absorbing light radiation and inhibiting the growth of essential bacteria and microbes, making their removal crucial for health of living beings and flora and fauna. This research endorsed a hydrothermal synthetic route for the photocatalyst CeO2/CdS/g-C3N4 @ZIF8 (or CCdGZ) fabrication to remove a set of hazardous dyes from wastewater streams. Corresponding Analytical methods evaluated the successfully developed CCdGZ photocatalyst's structural, morphological, and compositional properties. Powder X-ray photoelectron (PXRD) analysis showed the structural properties of CCdGZ and the quantum dot nature of the CeO2-CdS hybrid in the heterostructure with a crystallite size of 0.16 nm. The photocatalyst's optical responses were examined using UV–vis spectrophotometry and the UV-diffuse reflectance spectroscopy (UV-DRS) technique. Tauc's plot determined the energy band gap of the CCdGZ to be ∼2.64 eV, confirming a slight modification of the valence band (VB) and conduction band (CB) edges of the moieties CeO2, CdS, and g-C3N4. Thus, the heterostructure's moieties synergised to produce photocatalytic degradation. Under visible light irradiation, the photocatalyst CCdGZ photodegraded Victoria blue R (VBR) dye by 96.54% in 55 min. Photodegradation followed pseudo-first-order kinetics with a specific reaction rate of 0.06159 min−1 {coefficient of determination (R2) = 0.99847}. The corresponding TOC removal was 83.27%, while COD got reduced to 78.98% of its initial magnitude. Multiple reaction parameters, heterostructure reusability (over 89% efficient till the 5th run), the scavengers' experiment, inorganic ion effects, and water matrices were also evaluated. The study concludes with a photocatalytic reaction mechanism that explains the moieties' roles. This study designs a heterostructure photocatalyst that disintegrates emerging non-degradable organic pollutants in the UV–visible range, is recoverable, and has better photostability.

Pd and carbon quantum dots co-decorated TiO2 nanosheets for enhanced photocatalytic H2 production and reaction mechanism

TiO2-based composites are promising photocatalysts for efficient generation of the clean energy, H2, from water splitting. Herein, series of Pd nanoparticles and carbon quantum dots (CQDs) co-decorated TiO2 nanosheets (NSs), Pd-CQDs/TiO2, were designed by overall considering taking advantages of the three components: highly active TiO2 NSs, highly conductive CQDs and electron sink of Pd. Series of photocatalytic experiments were performed and the photocatalytic reaction mechanism was explored. The Pd-0.5CQDs/TiO2 exhibited an excellent photocatalytic hydrogen evolution rate (HER), which is 901.5, 41.8 and 1.7 times higher than those of the bare TiO2, 0.5CQDs/TiO2 and Pd/TiO2, respectively. The synergistic effect of the CQDs and Pd was found responsible for the enhanced photocatalytic activity of the Pd-0.5CQDs/TiO2. Besides, the CQDs was found facilitating complete conversion of Pd2+ to metallic Pd on the surface of TiO2 NSs, which may offer a new thought for design of other composite materials.

Round-the-clock photocatalysis of plasmonic Ag-enhanced Z-scheme heterojunction material Sr2MgSi2O7:(Eu, Dy)/g‑C3N4@Ag under visible-light irradiation

Self-luminous plasmonic photocatalysts Sr2MgSi2O7:(Eu, Dy)/g-C3N4@Ag were prepared using high-temperature sintering and photodeposition. Compared with pristine g-C3N4, the energy storage property of the long-afterglow luminescent material Sr2MgSi2O7:(Eu, Dy) and the noble metal Ag with localized surface plasmon resonance effect enable the composites to perform more excellent in round-the-clock photocatalytic degradation. The improved photocatalytic performance is attributed to the formation of Z-scheme heterojunction by Sr2MgSi2O7:(Eu, Dy) and g-C3N4, and to the fact that the loaded Ag nanoparticles broaden their visible-light absorption range and enable faster carrier transfer and more productive separation of electron-hole (e−-h+) pairs. According to various characterization outcomes and density functional theory calculations, possible pathways for electrons transfer during the photocatalytic reaction and possible mechanisms for the increasing of photocatalytic performance of Sr2MgSi2O7:(Eu, Dy)/g-C3N4@Ag composites are proposed. This work provides a targeted way for the optimization of round-the-clock heterojunction photocatalysts.

Photocatalytic removal of Cr(Ⅵ) and efficient degradation of tetracycline by oxygen-enriched vacancy pie-like NH2-MIL-125(Ti)

The heavy metals hexavalent chromium and tetracycline hydrochloride have caused considerable harm to the ecological environment of water. This has led to unprecedented requirements for the treatment and protection of the water environment. To address this problem, a cake—NH2-MIL-125(Ti)—was synthesised using a straightforward hydrothermal process, and NH2-MIL-125(Ti) catalysts with different oxygen vacancy concentrations (NMTi-OVs-X catalysts) were prepared through heat treatment. Cr(Ⅵ) and tetracycline hydrochloride (TCH) present in water were used as targets to analyse the samples’ ability to remove catalysis under sunlight. The experimental results indicate that the sample calcined at 300 °C for 300 min (NMTi-OVs-300) exhibits the highest catalytic activity. The effectiveness of TCH and Cr(VI) removal are 80 % and 100 % under simulated sunlight, respectively. Additionally, the reaction kinetic constant is 7.8 and 18.9 times higher than that of NH2-MIL-125(Ti). Proper defect sites contribute to the separation of photogenerated charges, enabling NMTi-OVs-300 to display satisfactory stability and excellent photocatalytic performance. The active substances were determined via electron spin resonance, and a photocatalytic reaction mechanism was suggested. This work provides a novel approach for the photocatalytic degradation of organic pollutants and Cr(VI) using a single semiconductor.

Preparation and Photocatalytic Properties of SnO2/C/PPy Composites

SnO2/C(Carbon)/PPy composites have been prepared by in situ polymerization using SnO2/C nanomaterials as the matrix. The structures and properties of as-synthesized samples were characterized by XRD, FT-IR, XPS, BET, SEM and TEM. Meanwhile, the photocatalytic reaction mechanism of SnO2/C/PPy composite for degradation of Rhodamine B (RhB) was analyzed. The photocatalytic tests indicated that the SnO2/C/PPy composites have excellent photocatalytic activity for RhB degradation under visible light irradiation and the RhB can be degraded to 90% within 20 min. The photocatalytic activity is still outstanding after five cycles and as-synthesized samples have emerged as powerful foundation for further industrial application.

Nanosheet g-C3N4 enhanced by Bi2MoO6 for highly efficient photocatalysts toward photodegradation of Rhodamine-B dye

The investigation of a proficient photocatalytic system for the degradation of organic pollutants holds significant importance in the field of environmental management. This study presents a binary type II heterojunction photocatalyst, Bi2MoO6/g-C3N4 which is synthesized using an eco-friendly ultrasonic-assisted method. Various characterization methods (XRD, FTIR, XPS, BET, TEM, UV–vis, and PL) are used to investigate the crystalline structures, composition, surface analysis, morphology, and optical properties of the photocatalyst. All the Bi2MoO6/g-C3N4 nanocomposites show better photocatalytic activity for Rhodamine B dye (Rh–B) degradation under Ultraviolet light irradiation than the pure g-C3N4. The photocatalytic activity of the 10 % Bi2MoO6/g-C3N4 nanocomposite is found to be the greatest among the tested samples. the 10 % Bi2MoO6/g-C3N4 nanocomposite demonstrates the ability to degrade 94.6 % of Rh–B (1 × 10−5 M) within 3 h, with a rate constant of 0.015 min–1. Notably, this rate constant is 7 times greater than that observed for pure g-C3N4, which has a rate constant of 0.00218 min–1. The effect of several reaction factors on the Rhodamine B (Rh–B) removal is studied. The enhanced photocatalytic activity of 10 % Bi2MoO6/g-C3N4 nanocomposite is mainly due to the formation of 2D/2D type II structures, increasing the active sites and the separation rate of photogenerated carriers. A possible photocatalytic reaction mechanism of Rhodamine B (Rh–B) degradation over Bi2MoO6/g-C3N4 is suggested based on active species trapping experiment. Moreover, the high stability and recyclability exhibited by the 10 % Bi2MoO6/g-C3N4 nanocomposite provide strong evidence supporting its suitability as a viable photocatalyst for wastewater treatment purposes.

Fabrication of visible-light induced fluorine doped bismuth oxide (Bi2O3-xFx) photocatalyst in degrading textile dyes from wastewater

Discharge of unused and untreated dye effluents into the environment by the textile industries is a major issue. In this wastewater, the methylene blue (MB) and methyl orange (MO) remain in a dissolved state along with various pollutants at different levels. To remove these dyes, visible light (λ ​≥ ​420 ​nm) active F (fluorine) doped bismuth oxide (Bi2O3-xFx) photocatalyst was synthesized through facile sol-gel method utilizing bismuth oxide (Bi2O3) and hydrofluoric acid (HF). Bi2O3-xFx demonstrated enhanced photocatalytic activity to decompose methylene blue (MB) and methyl orange (MO) under visible light. The F content in Bi2O3-xFx composite was optimized to 0.94 atom % with respect to organics decomposition. The study showed that enhanced photocatalytic activity of Bi2O3-xFx was ascribed due to participation of photo-induced electron (e¯)-hole (h+) in photocatalysis. The existence of hole (h+) and the generated °OH radical was experimentally confirmed in aqueous medium. The formation mechanism of these reactive species was explained on the basis of relative energy band position of Bi2O3-xFx and a detail photocatalytic decomposition reaction mechanism was proposed.

Construction of highly efficient CuS/CdS nanostructure for enhanced solar H2 evolution

The fabrication of efficient photocatalytic system for enhanced production of hydrogen is exceptionally thought-provoking.To address this issue herein we fabricated the CuS/CdS heterostructures by ultrasonication for photocatalytic H2 production. The structural integrity of the produced heterostructure is confirmed by the aid of analytical tools such as X-ray diffraction studies (XRD), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV–vis DRS), scanning electron microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The fabricated CuS/CdS sample exhibited the highest H2 production rate (824 μmol/g) than CuS (67 μmol/g) and CdS (135 μmol/g) under simulated solar illumination. The hydrogen output is noticeably enhanced due to improved absorption of visible light and competent charge carrier partition. It was confirmed by UV–vis diffuse reflectivity and photoluminescence spectra (PL) as charge carrier parting was effective as absorption of visible light was enhanced. A plausible photocatalytic H2 reaction mechanism has been elucidated from increased charge carrier division and visible light absorptivity. This work depicts a new approach for greatly resourceful nano architecture for energy-related applications.

Multipath charge transfer in Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons for enhanced photocatalytic amine oxidation

Hollow heterostructured catalysts have been widely investigated and applied in photocatalytic organic reactions. However, achieving hybrid catalysts with optimized hollow structure and controllable components is still a challenge. Herein, Cu-BTC@CuS@CeO2 ternary heterostructure hollow octahedrons were designed and prepared using a copper-based metal–organic framework (Cu-BTC) as both copper source and template. A thin CeO2 nanolayer was first formed and covered on the prepared Cu-BTC octahedron surface through a hydrothermal process. In the meanwhile, the Cu-BTC octahedrons were controllably etched in this hydrothermal process, leading to the formation of Cu-BTC@CeO2 hollow octahedron. The following sulfidation reaction produced Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons. Benefiting from the novel hollow octahedron double p-n heterojunctions, excellent visible-near infrared light absorption, and fast charge transfer and separation, the obtained Cu-BTC@CuS@CeO2 hollow octahedron hybrid catalyst exhibited a significantly higher photocatalytic activity toward the oxidative coupling of amines to imines at room temperature under visible-near infrared light irradiation compared to the control single component catalysts (Cu-BTC, CeO2, and CuS) and binary hybrid catalysts (Cu-BTC@CeO2, Cu-BTC@CuS, and CuS@CeO2). The enhanced charge transfer at the double p-n heterojunction was discussed. Meanwhile, the photocatalytic oxidation products and reaction mechanism were investigated by surface-enhanced Raman spectroscopy, gas chromatography-mass spectrometry, and pyridine adsorption FT-IR spectroscopy. This work presents a promising strategy for the design of multi-component hollow heterostructure catalysts.

Reusable and environmentally friendly cellulose nanofiber/titanium dioxide/chitosan aerogel photocatalyst for efficient degradation of tetracycline

Tetracycline antibiotics are currently detected in most water sources. The presence of such pollutants in the environment is becoming increasingly common, and addressing this contamination is a significant challenge due to its potential threat to human health and ecosystem stability. This study successfully prepared cellulose nanofiber/titanium dioxide/chitosan (CNF/TiO2/CS) aerogels by directional freeze-drying technique for photocatalytic degradation of tetracycline-contaminated wastewater. The CNF/TiO2/CS aerogel photocatalysts have a three-dimensional mesh structure with a large specific surface area, which provides many active sites for the highly efficient photocatalytic degradation of tetracyclines. The CNF/TiO2/CS aerogel showed 99.5% tetracycline removal efficiency within 180 min. Free radical scavenging experiments investigated the adsorption and photodegradation mechanism of tetracycline by CNF/TiO2/CS aerogel. The critical participation of •O2-and h+ in the decomposition of tetracycline was verified, which provided experimental support for the photocatalytic reaction mechanism. In addition, the CNF/TiO2/CS aerogel has high stability and recyclability for photocatalytic degradation, which can be recycled 7 times, and the recycling process is environmentally friendly. An in-depth analysis of the intermediate degradation products using liquid chromatography-mass spectrometry (LC-MS) revealed two efficient photocatalytic degradation pathways. These findings strongly confirm the extensive potential of photocatalytically active aerogels for wastewater treatment.

Graphdiyne (g-CnH2n-2) boosting electron transfer over rational design and construction of CuI/Ni-MOF photocatalyst for efficient hydrogen evolution

A CuI-graphdiyne/Ni-MOF ternary system was successfully constructed. Intially, CuI-graphdiyne was obtained by growth of GDY on the surface of CuI. Subequently, the CuI-graphdiyne was immobilized onto the surface of Ni-MOF using a simple physical stirring method. This, immobilization approach effectively reducing the accumulation of CuI-graphdiyne and increased the number of active sites for hydrogen evolution. Furthermore, a combination of various characterization techniques and energy band structures analysis was employed to propose the photocatalytic reaction mechanism between CuI and Ni-MOF. The proposed mechanism involves a Z-scheme heterojunction and suggests that the combination of CuI and Ni-MOF enhances the overall redox ability of the composite catalyst. By comparing CuI/Ni-MOF with CuI-graphdiyne/Ni-MOF, it was observed that the presence of graphdiyne as an electron-rich layer on CuI enhances the photocatalytic performance of CuI. Additionally, it facilitates electron transport between CuI and Ni-MOF, thereby improving the efficiency of photogenerated electron-hole complex separation. This experimental study provides valuable insight into the utilization of graphdiyne for enhancing transport in heterojunction.

Visible light photocatalysis: efficient Z-scheme LaFeO3/g-C3N4/ZnO photocatalyst for phenol degradation.

In this work, a Z-scheme LaFeO3/g-C3N4/ZnO heterojunction photocatalyst with large specific surface (68.758 m2/g) and low cost (0.00035 times the cost of per gram of Au) was easily synthesized by glucose-assisted hydrothermal method. The structure, surface morphology, and optical properties of the photocatalyst were investigated. The constructed Z-scheme heterojunction catalysts can enhance the visible light absorption and carrier separation efficiency. Among these photocatalysts, the 10%-LaFeO3/g-C3N4/ZnO composite possesses the premium performance for efficient degrading 97.43% of phenol within 120 min. Even after 5 cycles, it still sustains an excellent photocatalytic stability (92.13% phenol degradation). According to the XPS surface states and the capture of active species on LaFeO3/g-C3N4/ZnO, the electrons would be transferred from ZnO and LaFeO3 to g-C3N4. In addition, ·OH plays an important role in photocatalytic reactions for phenol degradation. Thus, the proposed possible photocatalytic reaction mechanism of Z-scheme LaFeO3/g-C3N4/ZnO can provide a more economical and efficient conception for phenol degradation.

Visible Light‐Driven Photocatalytic Transformation of Thiols to Disulfides in Water Catalyzed by Bi2S3

Selective coupling of thiols to produce disulfides is one very important and classic type of coupling reactions. Herein, an environmentally friendly and practical photocatalytic system for oxidative coupling of thiols to disulfides is developed. With no sacrificial agent, no additional additive, just sole water as solvent, performed in air at room temperature, excellent conversions of thiols and excellent selectivities of disulfides are obtained using a cheap and simple semiconductor material of bismuth sulfide (Bi2S3) under blue LED illumination. Excellent conversions and selectivities for coupling of thiols to produce disulfides are obtained, and the system is reusable. The as‐prepared photocatalyst is adequately characterized and the mechanism of photocatalytic reaction is discussed deeply.

One-pot citric acid/nitrates combustion design of 2D nanosheet mesoporous BiαClβOδ nanostructure: Efficient sunlight photocatalytic elimination of tetracycline-HCl

The development of high-efficiency and stable nano-photocatalysts for environmental pollution control is a rapidly evolving research domain. The fabrication of Z-scheme heterojunctions with exceptional redox abilities has emerged as a promising and effective approach. In this study, the Z-scheme heterojunction sheet-like photocatalyst was created using a one-pot citric acid/nitrates combustion method, consisting of BiαClβOδ. To optimize the photocatalyst's physicochemical properties, the synthesis process was conducted at different fuel to oxidizer ratios (Φ = 0.25, 0.5, 0.75, 1), which is a critical factor in the combustion reaction. Compared to the pristine BiOCl with a photocatalytic efficiency of 65%, heterojunction nanosheets with a Φ ratio of 0.5 exhibited superior performance in completely removing aqueous tetracycline-HCl under simulated solar light irradiation. This boosting performance is mainly due to the improved light harvesting (Eg = 2.52 eV), charge separation and transfer resulting from the Z-scheme structure, as well as the increased pore volume (0.565 cm3/g) and specific surface area (127.9 m2/g) and well-grown sheet-like morphology resulting from the high temperature, heat, and released gases during combustion. These characteristics were confirmed using various analytical techniques, including DRS, XRD, BET-BJH, FESEM, EDX, and TEM. Finally, the stability of the photocatalysts was tested, and a potential photocatalytic reaction mechanism based on a Z-scheme heterojunction was proposed.

Synthesis of oriented J type ZnIn2S4@CdIn2S4 heterojunction by controllable cation exchange for enhancing photocatalytic hydrogen evolution

Construction of semiconductor heterojunctions which promote the separation and transport of photogenerated carriers is an effective strategy for improving photocatalytic reaction efficiency. Based on the anisotropic electrical conductivity of layered ZnIn2S4 (ZIS) photocatalyst, an efficient heterojunction should be constructed along the layer plane of ZIS, that is, a J type heterojunction. However, achieving controllable synthesis of the oriented heterojunction of ZIS faces challenges. Herein, we develop a facile, cost-effective and spatially-selective cation exchange synthesis approach to construct J type ZnIn2S4@CdIn2S4 (J-ZIS@CIS) heterojunction using a flower-like hexagonal ZIS as the parent material. The developed synthesis approach can also control crystal structure of the heterojunction component CIS. This work presents a facile and controllable synthesis strategy to construct oriented anisotropic heterojunctions that are otherwise inaccessible. The as-prepared J-ZIS@CIS heterojunction displays a greatly enhanced photocatalytic hydrogen evolution activity with a rate of 183 μmol h−1, 2.77 times higher than that of pristine ZIS. Furthermore, the possible photocatalytic reaction mechanism is presented for the heterojunction.

A green synthetic approach for C/Ag@ urchin-like TiO2 nanocomposites showing a highly molar ratio CH4/CO for CO2 photoreduction

In the paper, the urchin-like TiO2 with rutile crystal structure was prepared under acidic conditions. When C powder was added in the reaction process, rutile TiO2 became rutile and anatase diphase structure. The yields of CH4 and CO of C/Ag@TiO2 were 5.46 μmol·g−1·h−1 and 1.51 μmol·g−1·h−1, respectively, and the molar ratio of CH4 was the highest for 78.3%. Through characterization of optical and electrical properties, the addition of C and Ag improved the optical performance, carrier concentration, and electron mobility. Finally, the photocatalytic reaction mechanism was proposed.

Noble Metal Modified TiO2 Hierarchically Structured Microspheres with Enhanced Photocatalytic Activity

Anatase TiO2 hierarchically structured microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method. The influences of reaction temperature on the morphology and crystallization of microspheres were investigated systematically. The obtained microspheres possessed better morphology and crystallization when the reaction temperature was 160 °C. Different noble metals (Au, Ag, Cu, Pt, Pd) were used for the microspheres modification, and the experimental results exhibited that the photocatalytic activities of the noble metal modified microspheres were enhanced obviously, especially for the Pt-modified sample (TPt), which showed the highest photocatalytic activity in degradation of tetracycline hydrochloride (the TPt sample showed the largest improvement, i.e., the activity reached 1.47 times higher than that of the bare sample) and hydrogen production (the largest improvement was also observed for the TPt sample, i.e., the activity was more than 30 times as the bare sample, reaching more than 300 μmol·g−1·h−1). Finally, a photocatalytic reaction mechanism involving the synergy of co-exposed {001}/{101} crystal facets with noble metals was proposed according to the as-obtained experimental results.