Insight into the activity of TiO2@nitrogen-doped hollow carbon spheres supported on g-C3N4 for robust photocatalytic performance

Elucidation of a Core-Shell Structure in Phenyl-Grafted Carbon Nitride/TiO2 Nanohybrids for Visible-Light-Mediated H2 Production with Simultaneous Rhodamine B Degradation

Dual-functional photocatalysts help to maximize resource utilization in water remediation, but often they are visible-light-inactive, toxic, and cost-intensive. Herein, a type-II heterojunction visible-light-active photocatalyst is reported for tandem degradation of Rhodamine B and generation of H2. A Rhodamine B degradation rate of 2.3 × 10-2 min-1 and H2 production activity of 5789 μmol h-1 g-1 are shown. The hybrid shows a gradient core-shell morphology with a visible - light-absorbing phenyl-modified carbon nitride (PhCN) core and a porous PhCN/TiO2 outer shell, resulting in an enhanced interaction between the catalyst and the surroundings. The nanoscale crystallization of TiO2 on PhCN's surface, shifts the triazine network structure, while autoclave treatments further increase the band gap and suppress charge carrier recombination. The influence of nanoscale morphological changes on photocatalytic activity was examined by varying the component ratios and thermal treatments, highlighting the strong correlation between the nanoscale architecture and the enhanced catalytic activity. This work provides a detailed guide to the exploration of environmentally friendly dual-functional photocatalysts.

Engineering yolk-double-shell Au@CN@ZnIn2S4 architecture with enhanced photocatalytic properties

The efficient utilization of light and the prolonged lifetime of photo-induced charge carriers are essential elements that contribute to superior photocatalytic activity. Yolk-shell nanostructures with porous shells and mobile cores offer significant structural advantages in achieving these goals. However, designing yolk-shell multicomponent nanocomposites with diverse architectures remains a persistent challenge. The present study involves the utilization of zinc indium sulfide (ZnIn2S4) flakes, which are uniformly incorporated into the yolk-shell Au@CN structure. The inclusion of ZnIn2S4 flakes in carbon nitride (CN) significantly enhances the performance of the overall system, allowing for efficient and rapid charge transfer. The uniform distribution of ZnIn2S4 flakes throughout the yolk-shell matrix ensures the catalytic activity is maximized, resulting in superior performance compared to conventional systems. The designed photocatalyst has a hollow interior which strengthens light absorption, a thin shell that shortens the electron migration distance, tight adhesion between shells, which makes it easier to separate and transfer carriers, and a movable Au core with localized surface plasmon resonance (LSPR) which can facilitate additional charge carrier generation for CN and ZnIn2S4. The yolk-shell microsphere composite of Au@CN@ZnIn2S4 shows a TC photodegradation rate of 72% within 2 h, which is more than double the photodegradation rate of hollow CN and ZnIn2S4. The present study's experimental demonstrations valuable insights into the rational design of sophisticated metal-semiconductors double yolk-shell nanocrystals, particularly those composed of metal sulfides cocatalyst, for superior photocatalytic applications.

Black Phosphorus-based Photocatalysts: Synthesis, Properties, and Applications

Photocatalysis is considered as an eco-friendly and sustainable strategy, since it uses abundant light for the advancement of the reaction, which is freely accessible and is devoid of environmental pollution. During the last decades, (nano)photocatalysts have gained broad industrial applications in terms of purification and detoxification of water as well as production of green fuels and hydrogen gas due to their special attributes. The degradation or remediation of toxic and hazardous compounds from the environment or changing them into non-toxic entities is a significant endeavor and necessary for the safety of humans, animals, and the environment. Black phosphorus (BP), a two-dimensional single-element material, has a marvelous structure, tunable bandgap, changeable morphology from bulk to nanosheet/quantum dot, and unique physicochemical properties, which makes it attractive material for photocatalytic applications, especially for sustainable development purposes. Since it can serve as a photocatalyst with or without coupling with other semiconductors, various aspects for multidimensional exploitation of BP are deliberated including their preparation via solvothermal, ball milling, calcination, and sonication methods to obtain BP from red phosphorus. The techniques for improving the photocatalytic and stability of BP-based composites are discussed along with their multifaceted applications for environmental remediation, pollution degradation, water splitting, N2 fixation, CO2 reduction, bacterial disinfection, H2 generation, and photodynamic therapy. Herein, most recent advancements pertaining to the photocatalytic applications of BP-based photocatalyst are cogitated, with a focus on their synthesis and properties as well as crucial challenges and future perspectives.

Facile synthesis of hollow spherical g-C3N4@LDH/NCQDs ternary nanostructure for multifunctional antibacterial and photodegradation activities

Heterojunction nanostructure construction and morphology engineering are considered to be effective approaches to improve photocatalytic performance. Herein, ternary hierarchical hollow structures consisting of cobalt-aluminum-layered double hydroxide (CoAl-LDH) nanoplates grown on hollow carbon nitride spheres (HCNS) and decorated with N-doped carbon quantum dots (NCQDs) were prepared using a templating method and a subsequent solvothermal process. The obtained HCNS@LDH/NCQD composites presented an improved performance in photocatalytic degradation of tetracycline and inactivation of E. coli compared with pure HCNS and LDH under visible light illumination. The enhanced photocatalytic activity of the designed photocatalyst could be attributed to the following reasons: (1) A special hollow structure provides more active sites and has multiple capabilities of light reflection by helping with a high specific surface area that improves the harvesting efficiency of solar light and (2) the strong synergistic effect among the constituents, which promotes separation and transfer of charge carriers and broadens the photo-response range.

Design of TiO2/Ag3BiO3 n-n heterojunction for enhanced degradation of tetracycline hydrochloride under visible-light irradiation

Pharmaceutical residual contaminants in aquatic ecosystems have caused severe risks to human health. Affordable, eco-friendly and effective photocatalysts to deal with these pollutants has become a hot topic in the scientific community. In this research, Ag₃BiO₃ nanoparticles were embedded on TiO₂ to form n-n heterojunction through a facile hydrothermal method. According to scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), brunauer emmett teller (BET), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) tests, the successful construction of TiO₂/Ag₃BiO₃ heterojunction is proved. TiO₂/Ag₃BiO₃ heterojunctions were employed as photocatalysts to remove tetracycline hydrochloride (TCH) under visible light irradiation in aqueous solution. Optimum TCH photodegradation efficiency was observed for TiO₂/Ag₃BiO₃ (10%), 15.4 times superior to that of TiO₂. The enhanced TCH photodegradation efficiency of TiO₂/Ag₃BiO₃ results from improved light absorption capacity and the reduction of recombination of photogenerated charge carriers via generation of n-n heterojunctions. The mechanism of increasing the photodegradation efficiency of TCH was determined by employing reactive species quenching experiments. TiO₂/Ag₃BiO₃ (10%) also exhibited an acceptable stability.

Semiconductors Application Forms and Doping Benefits to Wastewater Treatment: A Comparison of TiO2, WO3, and g-C3N4

Photocatalysis has been vastly applied for the removal of contaminants of emerging concern (CECs) and other micropollutants, with the aim of future water reclamation. As a process based upon photon irradiation, materials that may be activated through natural light sources are highly pursued, to facilitate their application and reduce costs. TiO2 is a reference material, and it has been greatly optimized. However, in its typical configuration, it is known to be mainly active under ultraviolet radiation. Thus, multiple alternative visible light driven (VLD) materials have been intensively studied recently. WO3 and g-C3N4 are currently attractive VLD catalysts, with WO3 possessing similarities with TiO2 as a metal oxide, allowing correlations between the knowledge regarding the reference catalyst, and g-C3N4 having an interesting and distinct non-metallic polymeric structure with the benefit of easy production. In this review, recent developments towards CECs degradation in TiO2 based photocatalysis are discussed, as reference catalyst, alongside the selected alternative materials, WO3 and g-C3N4. The aim here is to evaluate the different techniques more commonly explored to enhance catalyst photo-activity, specifically doping with multiple elements and the formation of composite materials. Moreover, the possible combination of photocatalysis and ozonation is also explored, as a promising route to potentialize their individual efficiencies and overcome typical drawbacks.

Nano-architectural design of TiO2 for high performance photocatalytic degradation of organic pollutant: A review

In the past several decades, significant efforts have been paid toward photocatalytic degradation of organic pollutants in environmental research. During the past years, titanium dioxide nano-architectures (TiO₂ NAs) have been widely used in water purification applications with photocatalytic degradation processes under Uv/Vis light illumination. Photocatalysis process with nano-architectural design of TiO₂ is viewed as an efficient procedure for directly channeling solar energy into water treatment reactions. The considerable band-gap values and the subsequent short life time of photo-generated charge carriers are showed among the limitations of this approach. One of these effective efforts is the using of oxidation processes with advance semiconductor photocatalyst NAs for degradation the organic pollutants under UV/Vis irradiation. Among them, nano-architectural design of TiO₂ photocatalyst (such as Janus, yolk-shell (Y@S), hollow microspheres (HMSs) and nano-belt) is an effective way to improve oxidation processes for increasing photocatalytic activity in water treatment applications. In the light of the above issues, this study tends to provide a critical overview of the used strategies for preparing TiO₂ photocatalysts with desirable physicochemical properties like enhanced absorption of light, low density, high surface area, photo-stability, and charge-carrier behavior. Among the various nanoarchitectural design of TiO₂, the Y@S and HMSs have created a great appeal given their considerable large surface area, low density, homogeneous catalytic environment, favorable light harvesting properties, and enhanced molecular diffusion kinetics of the particles. In this review was summarized the developments that have been made for nano-architectural design of TiO2 photocatalyst. Additional focus is placed on the realization of interfacial charge and the possibility of achieving charge carriers separation for these NAs as electron migration is the extremely important factor for increasing the photocatalytic activity.

Abiotic degradation behavior of polyacrylonitrile-based material filled with a composite of TiO2 and g-C3N4 under solar illumination

As some of the most promising alternatives to traditional non-degradable materials, photodegradable materials have advantages of environmental benignity and rapid degradation under simple conditions. In this work, nontoxic TiO₂ and cost-effective g-C₃N₄ have been compounded in a weight of 9:1 to form a photocatalytic additive with high activity. A 25 wt% loading of this photocatalytic additive has been incorporated into the polyacrylonitrile (PAN) by centrifugal electrospinning to prepare an abiotic degradable PAN material. Our results showed that the PAN chain could be almost fully degraded within 90 h in an aqueous medium under simulated sunlight in the absence of microorganisms. Product analysis implied that degradation of the PAN chain mainly involved the breaking of -CN and C-C bonds by radicals, followed by oxidation of terminal groups to carboxyl and gradual mineralization to CO₂ and H₂O. This design strategy may provide new insight for the production and degradation mechanism of photodegradable polymer.

Template-mediated copper doped porous g-C3N4 for efficient photodegradation of antibiotic contaminants

Graphite carbon nitride (g-C₃N₄) has great potential to treat antibiotic wastewater, but limited by small specific surface area, rapid recombination of photogenerated carriers and narrow visible light absorption range. In order to solve above problems, we designed a simple template-mediated approach by supramolecular self-assembly (Cu-melamine-cyanuric acid) to prepare copper doped porous graphitic carbon nitride (Cu-pCN) photocatalyst. The pre-organized template self-assembly driven by hydrogen bonds and electrostatic interaction, resulted in highly porous structure. The specific surface area of Cu-pCN increased to 142.8 m²/g from 11.37 m²/g of conventional bulk g-C₃N₄. In addition, the doping of Cu endowed them with better light absorption, higher separation and transfer rate of photogenerated carriers. Consequently, the obtained Cu-pCN displayed the superior photocatalytic degradation rate for tetracycline (TC) and high recycling stability.