Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Abstract

concentration for March 2021 was 417.14 parts per million (ppm), which is about 50% higher than the average for pre-industrial levels (i.e., 278 ppm). In order to control global warming, the CO 2 emission must fall by 25% to keep the temperature below 2 °C threshold relative to the pre-industrial climate. [3,4] Among the existing numerous renewable and sustainable energy resources such as wind, solar, hydropower, geo-thermal and ocean-energy, the consumption of unlimited solar energy become a vital alternative energy source, and has been extensively explored during the past few decades. [5] For instant, solar energy could be employed practically in photocatalysis for water splitting to generate hydrogen, carbon dioxide conversion to value added products, and pollutant oxidation. [6][7][8] Photocatalysis has advantage over conventional biological, incineration, electrocatalytic, adsorption, and air stripping treatment techniques because these methods always exhibit shortfalls such as instability, catalyst poisoning, low production yield, poor mechanical strength, time consuming, and electrode corrosion. [9,10] Generally, the photocatalytic process involves several essential steps such as the light absorption by photocatalyst to generate charge carriers, charge carrier's separation and migration to the photocatalyst surface, and the surface redox reactions to transform solar energy into chemical energy. [11,12] If these essential steps are satisfied by a proficient photocatalyst, then of course, high photocatalytic efficiency could be expected. Generally, the fundamental features of a photocatalyst include appropriate band gaps with their corresponding valence and conduction band potentials, surface active sites, surface area, and optical absorption behavior that govern the efficiency and effectiveness of photocatalytic processes. [13,14] Since the photocatalytic reactions are typically performed in water and air environments, therefore, the photocatalyst stability could be crucial under these circumstances. [15] Fujishima and Honda performed water splitting reaction for the first time in 1972, while utilizing TiO 2 photoanode with the aid of Pt as a counter electrode. [16] Afterward, TiO 2 photocatalyst received marvelous attention in photocatalysis owing to its promising features such as its non-toxic nature, water insolubility, nature abundant, hydrophilicity, high stability, and appropriate valence and conduction band potentials for redox reactions. [17] Yet, the Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photo catalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the stateof theart progress in the ...

A Novel Cu2O/ZnO@PET Composite Membrane for the Photocatalytic Degradation of Carbendazim

“…The current research in this area is aimed at developing new technologies for producing high-performance and low-cost catalysts. Various types of composite materials have attracted much research attention in the field of photocatalysis owing to their advantages, such as their design flexibility, improved physical and chemical properties and stability [ 17 , 18 , 19 , 20 , 21 ].…”

Activatable “Matryoshka” nanosystem delivery NgBR siRNA and control drug release for stepwise therapy and evaluate drug resistance cancer

“…Due to its high depth penetration and spatial/temporal resolution, photoacoustic (PA) imaging can guide drug release, localization, and diagnosis [ 77 , 78 ]. Carbon dots have great potential in PA bioimaging with low-cost sources and low cytotoxicity but are limited by visible light excitation [ 79 , 80 ]. The CPDs introduced in our research overcome these obstacles, it has ultra-high deep red/near-infrared emissivity, narrow full width at half maximum (FWHM) [ 57 ], and greatly improve the imaging contrast, it is of great significance as a laser emitting material.…”

Ni-Doped Ordered Nanoporous Carbon Prepared from Chestnut Wood Tannins for the Removal and Photocatalytic Degradation of Methylene Blue

“…Although titanium dioxide is widely reported to be one of the best photocatalysts for environmental purification due to its great photo-oxidative properties [ 28 , 29 , 30 , 31 , 32 , 33 ], nickel oxide has also proved to be very efficient in this extent [ 34 , 35 , 36 ]. Thus, the latter is known to be a p-type semiconductor with a band gap of 3.5 eV that is stable, non-toxic, and has high photocatalytic activity [ 34 , 35 , 36 ].…”

“…Thus, the latter is known to be a p-type semiconductor with a band gap of 3.5 eV that is stable, non-toxic, and has high photocatalytic activity [ 34 , 35 , 36 ]. Overall, the process of photocatalytic degradation appears to be very attractive, as it involves the production of highly active radicals that can unsystematically and rapidly decompose a wide range of pollutants, resulting in the formation of harmless products such as carbon dioxide and water [ 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Several mechanisms for the photocatalytic degradation of dyes have been suggested in literature [ 26 , 29 , 30 , 31 , 32 , 33 , 36 ].…”

“…Overall, the process of photocatalytic degradation appears to be very attractive, as it involves the production of highly active radicals that can unsystematically and rapidly decompose a wide range of pollutants, resulting in the formation of harmless products such as carbon dioxide and water [ 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Several mechanisms for the photocatalytic degradation of dyes have been suggested in literature [ 26 , 29 , 30 , 31 , 32 , 33 , 36 ]. One, where the dye adsorbed on the surface of the semiconductor photocatalyst absorbs a photon and excites an electron to the conduction band of the photocatalyst, followed by the reaction of this activated electron with the oxygen molecule to generate the reduced superoxide radical anion that further degrades the dye molecule to non-toxic products [ 30 , 36 ].…”