Search query: Principle of photocatalysis

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abstract: Although photocatalysis has been studied for many years as an attractive way to resolve energy and environmental problems, its principle still remains unclear. Some confusions and misunderstandings exist in photocatalytic studies. This research aims to elaborate some new thoughts on the fundamental principle of semiconductor photocatalysis. Starting from the basic laws of thermodynamics, we first defined the thermodynamic potential of photocatalysis. A concept, the Gibbs potential landscape, was thus then proposed to describe the kinetics of photocatalysis. Photocatalysis is therefore defined as a light driven chemical reaction that still needs heat activation, in that light and heat play their different roles and interact with each other. Photocatalysis should feature an activation energy functioning with both light and heat. The roles of light and heat are correlative and mutually inhibit at both levels of thermodynamics and kinetics, so it is impossible for an intrinsic light heat synergism to happen. Two criteria were further proposed to determine an intrinsic light heat synergism in photocatalysis. Experiments were also carried out to calculate the thermodynamic potential and can agree well with the theory. Experimental results proved that there is no intrinsic light heat synergism, in accordance with our theoretical prediction. This research clarified some misunderstandings and gained some new insights into the nature of photocatalysis; this is important for the discipline of semiconductor photocatalysis.
author_names: Baoshun Liu

Haowan Wu

Ivan P Parkin
title: New Insights into the Fundamental Principle of Semiconductor Photocatalysis
venue: ACS omega
year: 2020

abstract: Abstract Heterogeneous photocatalysis as a sustainable and promising strategy has been intensively investigated for different applications, including solar fuel production and degradation of environmental pollutants. However, it is still challenging to develop highly active, selective, and durable photocatalysts for practical applications. In this chapter, after introducing a brief history of photocatalysis, we first present a comprehensive review on the thermodynamics and dynamics of photocatalysis, which could help the readers deeply understand the fundamental principles of photocatalytic processes. Then, we systematically summarize the basics for the surface/interface science of photocatalysis, including adsorption, surface redox reactions, and interfacial charge separation. Finally, the design principles, modification strategies, and the characterization and evaluation methods of semiconductor photocatalysts are summarized. By addressing these pertinent and important topics in heterogeneous photocatalysis, this chapter is expected to provide a useful reference for researchers in designing and exploring advanced photocatalytic materials for different applications.
author_names: Xin Li

Jiaguo Yu

Chuanjia Jiang
title: Principle and surface science of photocatalysis
year: 2020

author_names: Bunsho Ohtani
title: Principle of Photocatalysis and Design of Active Photocatalysts
year: 2013

abstract: Abstract In the present paper, the electronic structure and the optical properties of metallic and nonmetallic elements doped ZnO were investigated based on the principle of photocatalysis by first principle density functional theory. Element doping shortens the band gap of ZnO. Due to the p type characteristics, Fe, Cu, B and N doping brings impurity states over the Fermi level of ZnO, resulting in the shortening of the band gap, extending the absorption and utilization of solar light and thus enhancing the photocatalytic properties of ZnO. However, no impurity states appear in the band gap of Cd and S doped ZnO due to the intrinsic doping of Cd and S. Further investigations indicate that different doping atoms can indeed alter the near Fermi level density of states (DOS) of ZnO and their electronic structures via substitution of zinc and oxygen atoms. In addition, the optical properties of ZnO are improved after doped with different atoms by comparing with those of pure ZnO. Due to the difference of their outer shell electrons of the doped atoms, the optical absorption properties of the investigated materials are followed as the following order: Fe /B doped ZnO Cu /N doped ZnO Cd /S doped ZnO pure ZnO.
author_names: Chang Feng

Zhuoyuan Chen

Weibing Li

Fan Zhang

Xiang-bo Li

Likun Xu

Mingxian Sun
title: First principle calculation of the electronic structures and optical properties of the metallic and nonmetallic elements doped ZnO on the basis of photocatalysis
venue: Physica B: Condensed Matter
year: 2019

abstract: Due to the increase of emerging contaminants in water, how to use new treatment technology to make up for the defects of traditional wastewater treatment method has become one of the research hotspots at present. Intimate coupling of photocatalysis and biodegradation (ICPB) as a novel wastewater treatment method, which combines the advantages of biological treatment and photocatalytic reactions, has shown a great potential as a low cost, environmental friendly and sustainable treatment technology. The system mainly consists of photocatalytic materials, porous carriers and biofilm. The key principle of ICPB is to transform bio recalcitrant pollutants into biodegradable products by photocatalysis on the surface of porous carriers. The biodegradable products were mineralized simultaneously through the biofilm inside the carriers. Because of the protection of the carriers, the microorganism can remain active even under the UV light, the mechanical force of water flow or the attack of free radicals. ICPB breaks the traditional concept that photocatalytic reaction and biodegradation must be separated in different reactors, improves the purification capacity of sewage and saves the cost. This review summarizes the recent advances of ICPB photocatalysts, carriers and biofilm being applied, and focuses on the mechanisms and reactor configurations which is particularly novel. Furthermore, the possible ongoing researches on ICPB are also put forward. This review will provide a valuable insight into the design and application of ICPB in environment and energy field.
author_names: Mingliang Yu

Jiajia Wang

Lin Tang

Chengyang Feng

Haoyu Liu

Hongxing Zhang

Bo Peng

Zhaoming Chen

Qingqing Xie
title: Intimate coupling of photocatalysis and biodegradation for wastewater treatment: Mechanisms, recent advances and environmental applications.
venue: Water research
year: 2020

abstract: Herein, we report on the structural design principle of small molecule organic semiconductors as metal free, pure organic and visible light active photocatalysts. Two series of electron donor and acceptor type organic semiconductor molecules were synthesized to meet crucial requirements, such as 1) absorption range in the visible region, 2) sufficient photoredox potential, and 3) long lifetime of photogenerated excitons. The photocatalytic activity was demonstrated in the intermolecular C H functionalization of electron rich heteroaromates with malonate derivatives. A mechanistic study of the light induced electron transport between the organic photocatalyst, substrate, and the sacrificial agent are described. With their tunable absorption range and defined energy band structure, the small molecule organic semiconductors could offer a new class of metal free and visible light active photocatalysts for chemical reactions.
author_names: L Wang

Wei Huang

Run Li

Dominik W Gehrig

Paul W M Blom

Katharina Landfester

Kai A I Zhang
title: Structural Design Principle of Small Molecule Organic Semiconductors for Metal Free, Visible Light Promoted Photocatalysis.
venue: Angewandte Chemie
year: 2016

abstract: In the recent research on photocatalysis, the conversion of green and sustainable technology has received increasing attention due to its potential to solve energy problem in an eco friendly approach. The present review focuses on highly efficient and low cost photocatalysts and various metal free photocatalytic materials that have been designed and developed in recent years for energy conversion and environmental purification as a result of their unique properties and characteristics. This critical review presents the recent crucial applications and progress in metal free photocatalysis, including Water splitting using few layer C 2N, Renewable energy production using photofuelcells, Water purification using UV light, Deodorizing effect, Air purifying effect, Anti fogging and self cleaning as well as Hazardous waste remediation. The review concludes with suggestions for future research topics. It is hoped that this review will facilitate deep level investigation on the subject and provide new opportunities to develop metal free photocatalytic materials with other important applications in the nearest future.
author_names: Tawakalitu Ajibola

L Salami

Alaba Elizabeth Akin-Johnson

Nafiu Olatunbosun Ashiru

Kunle Akinluwade

E A Arikawe
title: Metal Free Photocatalysis: Principle and Application in Energy Conversion and Purification
year: 2019

abstract: With the increasing consumption of fossil energy, more and more refractory pollutants are released into the environment. Using eco friendly ways to treat the pollutants and gain energy is urgently needed. By using microbial fuel cells (MFCs) contaminant degradation and energy recovery can be achieved simultaneously but limited by the finite kinds of degradation of pollutants and the low power production efficiency. To promote the energy productivity and pollutant degradation ability, some researchers are focused on introducing solar energy into the system. Some semiconductors can absorb solar energy and convert it into electricity. Meanwhile, the typical structure of the photo excited semiconductor can improve the performance of contaminant removal. Another ideal energy convention way is the photosynthesis. Some researchers use aquatic microalgae to harness the solar energy and then release the energy by MFC. In addition to producing oxygen and capturing CO2 and other nutrient, the microalga is a promising combination material. The coupling system of MFC and one of semiconductors or microalgae can be seen as microbial photo electro chemical cell (MPEC) systems. The development background and research advances on MPECs are briefly introduced in this chapter. The existing coupling forms of the technology are classified, and the coupling mechanisms of various forms are explained in detail. Finally, the future development of this coupling technology is prospected.
author_names: Wang Shusen

Hafiz Muhammad Adeel Sharif

Haowen Cheng

Aijie Wang
title: Bioelectrochemical System Integrated with Photocatalysis: Principle and Prospect in Wastewater Treatment
year: 2019

abstract: Self doping by Ti3+ and introducing oxygen vacancies in TiO2 is an important and effective strategy to extend its optical absorption from the UV into the visible region. In this paper, we report the synthesis of a series of Ti3+ self doped TiO2 nanocrystals via a hydrothermal method using TiCl3 and (NH4)2TiF6 as the source of Ti3+ and Ti4+ respectively. The oxidation of Ti3+ can be inhibited by (NH4)2TiF6 based on Le Chatelier's principle. The samples are characterized by X ray diffraction, UV Vis diffuse reflectance spectroscopy, X ray photoelectron spectroscopy, electron paramagnetic resonance, field emission scanning electron microscopy and transmission electron microcopy, respectively. The results indicate that Ti3+ is localized in the bulk of the as prepared TiO2 nanocrystals, rather than on the surface. In comparison with pristine TiO2, the Ti3+ self doped TiO2 nanocrystals exhibit an enhanced photocatalytic activity of 86.3% towards the photodegradation of methylene blue solution under simulated solar light irradiation and 99% under natural solar irradiation. It is found that the molar ratio of Ti4+/Ti3+ used during the synthesis has significant effects on the photocatalytic activity of Ti3+ self doped TiO2 photocatalysts, since the electronic structures of the resulting Ti3+ self doped TiO2 nanocrystals can be finely tuned by changing the ratios. The significantly enhanced photocatalytic activity should be due to the self doping of Ti3+ in TiO2 nanocrystals, which not only increases the optical absorption in the visible light region, but also helps to spatially separate the photogenerated charge carriers.
author_names: Maoqin Qiu

Yuan Tian

Zhangxian Chen

Zeheng Yang

Li Wenming

Kai Wang

Lei Wang

Kun Wang

Weixin Zhang
title: Synthesis of Ti3+ self doped TiO2 nanocrystals based on Le Chatelier's principle and their application in solar light photocatalysis
year: 2016

abstract: Hollow structured polyhedral nanostructures of AgI nanoboxes and cube tetrapod Ag/AgI cages have been fabricated through the controlled reaction of I ions with nanocubes and cube tetrapods of AgCl based on the principle of the Kirkendall effect. The Ag0 nanodomains in the source nanoparticles of AgCl:Ag are preserved in the final hollow Ag/AgI cages during the chemical conversion of AgCl to AgI. The obtained hollow cube tetrapod Ag/AgI nanostructures exhibited enhanced light absorption in the visible region and photocatalytic performance towards hydrogen evolution from water reduction and decomposition of organic pollutants, owing to the contribution of the surface plasmon resonance (SPR) effect of silver nanoparticles (nanodomains) The present versatile route can be generalized to the preparation of other inorganic functional materials with hollow interiors for different applications.
author_names: Changhua An

Jizhuang Wang

Junxue Liu

Shutao Wang

Qinhui Zhang
title: Plasmonic enhancement of photocatalysis over Ag incorporated AgI hollow nanostructures
year: 2014