Recent Advances in Doped Bi2O3 and its Photocatalytic Activity: A Review

Bismuth Oxide (Bi2O3) has a very promising photocatalytic ability to degrade waste pollutants under visible light irradiation because it has a small energy gap of around 2.85-2.58 eV. Although it has excellent potential as a photocatalyst, Bi2O3 has the disadvantage of a high electron-hole pair recombination rate, which will reduce its photocatalytic activity. To overcome these problems, surface modifications, defect recognition, or doping of Bi2O3 are carried out to obtain a more effective and efficient photocatalyst to degrade waste pollutants under visible light irradiation. Several studies by researchers have been described for the modification of Bi2O3 by doping. Various types of doping are given, such as doping in elements or doping in the form of compounds to form composites. Based on several studies that have been described, appropriate doping has been shown to increase the photocatalytic activity of Bi2O3. Keywords: Bi2O3, Photocatalyst, Doping

A Mini-Review on Nanostructured g-C3N4 Photocatalysts for Solar Fuel Production

Graphitic carbon nitride (g-C3N4) is an important photocatalytic material that receives a lot of research attention globally. This is because of its favourable thermal and chemical stability as well as electronic band structure. However, the photocatalytic performance of the bulk g-C3N4 is limited by fast recombination of electron-hole pair and poor visible light-harvesting ability. Thus, different strategies, such as heterostructuring, nanotuning, doping, etc., have been adopted to overcome the aforementioned challenges to enhance the photocatalytic performance of g-C3N4. In recent times, various nanostructured g-C3N4 photocatalytic materials with various tuned morphologies have been designed and fabricated in literature for different photocatalytic activities. This mini-review summarized the progress development of nanostructured g-C3N4 photocatalysts with various tuned morphologies for solar fuel generation. The article briefly highlights the research status of various g-C3N4 with tuned morphologies and enhanced solar fuel generation abilities. Finally, a conclusion and future research were also suggested, opening up new areas on g-C3N4 photocatalysis.

Hydrogen evolution via noble metals based photocatalysts: A review

In recent decades, the use of photocatalysts in the evolution of hydrogen (H2) has received much attention. However, the use of the well-known titanium oxide and another photocatalyst as a base for noble metals is limited due to their major weakness in electron-hole pair separation. The use of cocatalysts can be a good way to overcome this problem and provide better performance for the evolution of hydrogen. In this review, suitable high-efficiency cocatalysts for solar hydrogen production have been thoroughly reviewed. New strategies and solutions were examined in terms of increasing the recombination of charge carriers, designing reactive sites, and enhancing the wavelengths of light absorption. Several new types of cocatalysts based on semiconductors in noble groups and dual metals have been evaluated. It is expected that these photocatalysts will be able to reduce the activation energy of reaction and charge separation. In this regard, the existing views and challenges in the field of photocatalysts are presented. The characteristics of monoatomic photocatalysts are reviewed in this manuscript and the latest advances in this field are summarized. Further, the future trends and upcoming research are also briefly discussed. Finally, this review presents noble metal-based photocatalysts for providing suitable photocatalysts on a larger scale and improving their applicability.

Low-Dimensional CsPbBr3@CoBr2 Super-Nanowire Structure for Perovskite/PMMA Composite with Highly Blue Emissive Performance

In this study, low-dimensional CsPbBr3@CoBr2 super-nanowire (SNW) structures were synthesized via a one-pot heating strategy for highly blue emissions. By introducing CoBr2 to CsPbBr3 precursors, the shape of perovskite nanocrystals was changed from cuboids to a super-nanowire structure, as revealed through a transmission electron microscope. SNWs were formed from stacked segments of nano-plates (lateral dimension of 10–12 nm and thickness of ~2.5 nm) with lengths of several microns. The fabricated sample absorbs light at a wavelength of <450 nm, and it is emitted at a wavelength of 475 nm. It also has a radiant flux conversion efficiency of up to 85% when stimulated by a 430 nm LED light source. The average decay time of up to 80 µs indicates that they effectively prevent the recombination of electron–hole pair. The optical performance still remains over 65% when the ambient temperature is up to 120 °C compared with that under room temperature. The excellent color purity, optical quantum efficiency, long carrier lifetime, and thermal stability make CsPbBr3@CoBr2 SNWs highly promising for a range of photolumicescence applications, such as a high color rendering index lighting and transparent blue emissive screen.

Carbon nanotubes as electronic mediators combined with Bi2MoO6 and g-C3N4 to form Z-scheme heterojunctions to enhance visible light photocatalysis

In this paper, Z-scheme Bi2MoO6/CNTs/g-C3N4 composite-photocatalysts were prepared through a simple hydrothermal method. The analysis was performed by XRD, FT-IR, SEM, EDS, TEM, HRTEM, XPS, BET, UV-Vis diffuse reflectance and PL spectrums. Various analyses show that CNTs not only act as excellent charge transfer bridges, but also enable the formation of a Z-scheme of charge transfer mechanism between Bi2MoO6 and g-C3N4. This process not only effectively isolates electrons and holes, but also prolongs electron-hole pair lifetimes, resulting in a substantial improvement in the photocatalytic performance of the composite photocatalyst. Best photocatalytic degradation performance was shown by Bi2MoO6/CNTs/g-C3N4 composite photocatalyst under simulated sunlight, while the composite photocatalyst still maintained extremely high degradation performance in cycling tests.

Nanostructure Engineering via Intramolecular Construction of Carbon Nitride as Efficient Photocatalyst for CO2 Reduction

Light-driven heterogeneous photocatalysis has gained great significance for generating solar fuel; the challenging charge separation process and sluggish surface catalytic reactions significantly restrict the progress of solar energy conversion using a semiconductor photocatalyst. Herein, we propose a novel and feasible strategy to incorporate dihydroxy benzene (DHB) as a conjugated monomer within the framework of urea containing CN (CNU-DHBx) to tune the electronic conductivity and charge separation due to the aromaticity of the benzene ring, which acts as an electron-donating species. Systematic characterizations such as SPV, PL, XPS, DRS, and TRPL demonstrated that the incorporation of the DHB monomer greatly enhanced the photocatalytic CO2 reduction of CN due to the enhanced charge separation and modulation of the ionic mobility. The significantly enhanced photocatalytic activity of CNU–DHB15.0 in comparison with parental CN was 85 µmol/h for CO and 19.92 µmol/h of the H2 source. It can be attributed to the electron–hole pair separation and enhance the optical adsorption due to the presence of DHB. Furthermore, this remarkable modification affected the chemical composition, bandgap, and surface area, encouraging the controlled detachment of light-produced photons and making it the ideal choice for CO2 photoreduction. Our research findings potentially offer a solution for tuning complex charge separation and catalytic reactions in photocatalysis that could practically lead to the generation of artificial photocatalysts for efficient solar energy into chemical energy conversion.

The X-ray Sensitivity of an Amorphous Lead Oxide Photoconductor

The photoconductor layer is an important component of direct conversion flat panel X-ray imagers (FPXI); thus, it should be carefully selected to meet the requirements for the X-ray imaging detector, and its properties should be clearly understood to develop the most optimal detector design. Currently, amorphous selenium (a-Se) is the only photoconductor utilized in commercial direct conversion FPXIs for low-energy mammographic imaging, but it is not practically feasible for higher-energy diagnostic imaging. Amorphous lead oxide (a-PbO) photoconductor is considered as a replacement to a-Se in radiography, fluoroscopy, and tomosynthesis applications. In this work, we investigated the X-ray sensitivity of a-PbO, one of the most important parameters for X-ray photoconductors, and examined the underlying mechanisms responsible for charge generation and recombination. The X-ray sensitivity in terms of electron–hole pair creation energy, W±, was measured in a range of electric fields, X-ray energies, and exposure levels. W± decreases with the electric field and X-ray energy, saturating at 18–31 eV/ehp, depending on the energy of X-rays, but increases with the exposure rate. The peculiar dependencies of W± on these parameters lead to a conclusion that, at electric fields relevant to detector operation (~10 V/μm), the columnar recombination and the bulk recombination mechanisms interplay in the a-PbO photoconductor.