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abstract: Abstract A large variety of electrochemical advanced oxidation processes (EAOPs) have been recently developed to remove organic pollutants from wastewaters to avoid their serious health risk factors from their environmental accumulation and to reuse the treated water for human activities. The effectiveness of EAOPs is based on the in situ production of strong reactive oxygen species (ROS) like hydroxyl radical OH) Photoelectrocatalysis (PEC) has emerged as a promising powerful EAOP by combining photocatalytic and electrolytic processes. It consists in the promotion of electrons from the valence band to the conduction band of a semiconductor photocatalyst upon light irradiation, with production of positive holes. The fast recombination of the electron/hole pairs formed is avoided in PEC by applying an external bias potential to the photocatalyst that extracts the photogenerated electrons up to the cathode of the electrolytic cell. Organics can be oxidized directly by the holes, *OH formed from water oxidation with holes and other ROS produced between the electrons and dissolved O2. This paper presents a general and critical review on the application of PEC to the remediation of wastewaters with organic pollutants. Special attention is made over the different kinds of photocatalysts utilized and preparation methods of the most ubiquitous TiO2 materials. Typical PEC systems and main operation variables that affect the effectiveness of the degradation process are also examined. An exhaustive analysis of the advances obtained on the treatment of dyes, chemicals and pharmaceuticals from synthetic solutions, as well as of real wastewaters, is performed. Finally, research prospects are proposed for the future development of PEC with perspectives to industrial application.
author_names: Sergi Garcia-Segura

Enric Brillas
title: Applied photoelectrocatalysis on the degradation of organic pollutants in wastewaters
year: 2017

abstract: To meet the ever increasing global demand for energy, conversion of solar energy to chemical/thermal energy is very promising. Light mediated catalysis, including photocatalysis (organic transformations, water splitting, CO2 reduction, etc. and photothermal catalysis play key roles in solar to chemical/thermal energy conversion via the light matter interaction. The major challenges in traditional semiconductor photocatalysts include insufficient sunlight utilization, charge carrier recombination, limited exposure of active sites, and particularly the difficulty of understanding the structure activity relationship. Metal organic frameworks (MOFs) featuring semiconductor like behavior, have recently captured broad interest toward photocatalysis and photothermal catalysis because of their well defined and tailorable porous structures, high surface areas, etc. These advantages are beneficial for rational structural modulation for improved light harvesting and charge separation as well as other effects, greatly helping to address the aforementioned challenges and especially facilitating the establishment of the structure activity relationship. Therefore, it is increasingly important to summarize this research field and provide in depth insight into MOF based photocatalysis and photothermal catalysis to accelerate the future development. In this Account, we have summarized the recent advances in these two directly relevant applications, photocatalysis and photothermal catalysis, mainly focusing on the results in our lab. Given the unique structural features of MOFs, we have put an emphasis on rational material design to optimize the components and performance and to understand related mechanisms behind the enhanced activity. This Account starts by presenting an overview of solar energy conversion by catalysis. We explain why MOFs can be promising photocatalysts and exemplify the semiconductor like behavior of MOFs. More importantly, we show that MOFs provide a powerful platform to study photocatalysis, in which the involved three key processes, namely, light harvesting, electron hole separation, and surface redox reactions, can be rationally improved. Meanwhile, the structure activity relationship and charge separation dynamics are illustrated in this part. In addition, MOFs for photothermal catalysis have been introduced that are based on the photothermal effect of plasmonic metals and/or MOFs, together with light driven electronic state optimization of active sites, toward enhanced heterogeneous organic reactions. Finally, our brief outlooks on the current challenges and future development of MOF photocatalysis and photothermal catalysis are provided. It is believed that this Account will afford significant understanding and inspirations toward solar energy conversion over MOF based catalysts.
author_names: Juan-Ding Xiao

Hai-Long Jiang
title: Metal Organic Frameworks for Photocatalysis and Photothermal Catalysis.
venue: Accounts of chemical research
year: 2019

abstract: Semiconductor polymeric graphitic carbon nitride (g C3N4) photocatalysts have attracted dramatically growing attention in the field of the visible light induced hydrogen evolution reaction (HER) because of their facile synthesis, easy functionalization, attractive electronic band structure, high physicochemical stability and photocatalytic activity. This review article presents a panorama of the latest advancements in the rational design and development of g C3N4 and g C3N4 based composite photocatalysts for HER application. Concretely, the review starts with the development history, synthetic strategy, electronic structure and physicochemical characteristics of g C3N4 materials, followed by the rational design and engineering of various nanostructured g C3N4 (e.g. thinner, highly crystalline, doped, and porous g C3N4) photocatalysts for HER application. Then a series of highly efficient g C3N4 (e.g. metal/g C3N4, semiconductor/g C3N4, metal organic framework/g C3N4, carbon/g C3N4, conducting polymer/g C3N4, sensitizer/g C3N4) composite photocatalysts are exemplified. Lastly, this review provides a comprehensive summary and outlook on the major challenges, opportunities, and inspiring perspectives for future research in this hot area on the basis of pioneering works. It is believed that the emerging g C3N4 based photocatalysts will act as the "holy grail" for highly efficient photocatalytic HER under visible light irradiation.
author_names: Guangfu Liao

Yan Gong

Li Zhang

Haiyang Gao

Guan-Jun Yang

Baizeng Fang
title: Semiconductor polymeric graphitic carbon nitride photocatalysts: the "holy grail" for the photocatalytic hydrogen evolution reaction under visible light
year: 2019

abstract: Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field effect transistors (OFETs) light emitting diodes (OLEDs) and photovoltaic cells (OPVs) Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state of art status and guide future work in this area.
author_names: Chengliang Wang

Huanli Dong

Lang Jiang

Wenping Hu
title: Organic semiconductor crystals.
venue: Chemical Society reviews
year: 2018

abstract: Abstract Graphitic carbon nitride (g C3N4) as a fascinating visible light active semiconductor photocatalyst has medium band gap, non toxic nature, stable chemical structure and high thermal stability. Recently, intensive researches are focused on photocatalytic activity of g C3N4 for wastewater treatment. This review demonstrates latest progress in fabrication of graphitic carbon nitride C3N4 incorporated nanocomposite to explore photocatalytic ability for water purification. The g C3N4 based nanocomposites were categorized as g C3N4 metal free nanocomposite, noble metals/g C3N4 heterojunction, non metal doped g C3N4, transition and post transition metal based g C3N4 nanocomposite. Apart from fabrication methods, we emphasized on elaborating the mechanism of activity enhancement during photocatalytic process.
author_names: Anita Sudhaik

Pankaj Raizada

Pooja Shandilya

Dae-Yong Jeong

Ji-Ho Lim

Pardeep Singh
title: Review on fabrication of graphitic carbon nitride based efficient nanocomposites for photodegradation of aqueous phase organic pollutants
year: 2018

abstract: Organic semiconducting single crystals (OSSCs) are ideal candidates for the construction of high performance optoelectronic devices/circuits and a great platform for fundamental research due to their long range order, absence of grain boundaries, and extremely low defect density. Impressive improvements have recently been made in organic optoelectronics: the charge carrier mobility is now over 10 cm2 V 1 s 1 and the fluorescence efficiency reaches 90% for many OSSCs. Moreover, high mobility and strong emission can be integrated into a single OSSC, for example, showing a mobility of up to 34 cm2 V 1 s 1 and a photoluminescence yield of 41.2% These achievements are attributed to the rational design and synthesis of organic semiconductors as well as improvements in preparation technology for crystals, which accelerate the application of OSSCs in devices and circuits, such as organic field effect transistors, organic photodetectors, organic photovoltaics, organic light emitting diodes, organic light emitting transistors, and even electrically pumped organic lasers. In this context, an overview of these fantastic advancements in terms of the fundamental insights into developing high performance organic semiconductors, efficient strategies for yielding desirable high quality OSSCs, and their applications in optoelectronic devices and circuits is presented. Finally, an overview of the development of OSSCs along with current challenges and future research directions is provided.
author_names: Xiaotao Zhang

Huanli Dong

Wenping Hu
title: Organic Semiconductor Single Crystals for Electronics and Photonics.
venue: Advanced materials
year: 2018

abstract: Abstract Semiconductor photocatalyst mediated advanced oxidation processes are regarded as one of the most efficient technologies to mitigate organic pollutants in water. However, poor activity under visible light and the recombination of photogenerated electron and hole pairs hinder large scale applicability of semiconductor photocatalysts for water purification. The modification of semiconductor photocatalysts with carbon quantum dots (CQDs) is of high importance due to low toxicity, aqueous stability, enhanced surface area, economic feasibility, good biocompatibility and chemical inertness of CQDs. In this review, we highlight strategies to improve the activity of conventional semiconductor photocatalysts via coupling with CQDs. The enhanced photocatalytic activity of CQD modified narrow and wide band gap photocatalysts is due mainly to up conversion photoluminescence (UPCL) and the electron reservoir properties of CQDs, while in the case of Z scheme photocatalysts CQDs act as an electron mediator. Finally, a conclusive outlook and suggested research directions are provided to address challenges such as the inadequate separation of photoinduced charge carriers.
author_names: Sheetal Sharma

Vishal Dutta

Pardeep Singh

Pankaj Raizada

Abolfazl Rahmani-Sani

Ahmad Hosseini-Bandegharaei

Vijay Kumar Thakur
title: Carbon quantum dot supported semiconductor photocatalysts for efficient degradation of organic pollutants in water: A review
venue: Journal of Cleaner Production
year: 2019

abstract: Metal organic frameworks (MOFs) with low density, high porosity, and easy tunability of functionality and structural properties, represent potential candidates for use as semiconductor materials. The rapid development of the semiconductor industry and the continuous miniaturization of feature sizes of integrated circuits toward the nanometer (nm) scale require novel semiconductor materials instead of traditional materials like silicon, germanium, and gallium arsenide etc. MOFs with advantageous properties of both the inorganic and the organic components promise to serve as the next generation of semiconductor materials for the microelectronics industry with the potential to be extremely stable, cheap, and mechanically flexible. Here, a perspective of recent research is provided, regarding the semiconducting properties of MOFs, bandgap studies, and their potential in microelectronic devices.
author_names: Muhammad Usman

Shruti Mendiratta

Kuang-Lieh Lu
title: Semiconductor Metal Organic Frameworks: Future Low Bandgap Materials.
venue: Advanced materials
year: 2017

abstract: Abstract Organic pollutants' treatment in wastewater has attracted extensive attention due to its degradation resistance and potentially hazardous to human health. Some organic matters such as persistent organic pollutants (POPs) could exist in environment and resist to decomposition, which may cause chronic intoxication or even cancers. Because photocatalytic technique is efficient, nontoxic, and cost effective to degrade organic pollutants, some semiconductors including TiO2 and ZnO as photocatalysts have aroused wide public concern. CeO2 has been reported as an efficient photocatalyst in contrast to TiO2 owing to its high oxygen storage, eco friendly properties and photostability. But inefficient utilization of solar energy due to its intrinsic wide bandgap restrains its further application in real environmental pollutant treatment. In order to improve photocatalytic performances of CeO2, some modifications have been developed such as doping ions, coupling with semiconductor and construction of CeO2 based solid solution. The purpose of this review is to introduce these techniques, reveals its fundamental mechanisms and the recent researches about photodegradation of organic pollutants in wastewater over CeO2 based photocatalysts. Besides, this review will evaluate the photocatalytic performance for organic pollutants and outlook the challenges and prospects in the future.
author_names: Ran Ma

Sai Zhang

Tao Wen

Pengcheng Gu

Lei Li

Guixia Zhao

Fenlei Niu

Qifei Huang

Zhenwu Tang

Xiangke Wang
title: A critical review on visible light response CeO2 based photocatalysts with enhanced photooxidation of organic pollutants
venue: Catalysis Today
year: 2019

abstract: Abstract Among the admired photocatalysts, metal sulphide based semiconductors are most prominent photocatalysts for the degradation or decomposition of dyes in wastewater industries with low cost, environment friendly and sustainable treatment technologies for the environmental protection. In recent years, the environmental pollution poses a serious threat to the environment and public health. To overcome the environmental pollution, doped and heterojunction based semiconductor metal sulfide nanostructures (MSNSs) are developed as photocatalysts for the purpose of photocatalytic degradation or removal of large organic dyes in an eco friendly and sustainable fashion. This comprehensive review starts with a brief overview on dyes as pollutants, dyes classification, dyes decolorization or degradation strategies and focuses on the mechanisms involved in comparatively well understood MSNSs photocatalysts such as ZnS, CdS, CuS, Ag2S, Bi2S3, CoS, FeS, and PbS etc. It particularly discusses the recent advancements to enhance photocatalytic degradation of toxic dyes by using various MSNSs to make it a flexible and cost effective commercial dye treatment technology. In addition, we have focused on the treatment of organic dyes using different types of MSNSs by photocatalysis and the effects of various parameters such as dopants, heterojunctions, band gap, size, light intensity, surface area, reaction time, and degradation efficiency, etc. are highlighted.
author_names: Dasari Ayodhya

Guttena Veerabhadram
title: A review on recent advances in photodegradation of dyes using doped and heterojunction based semiconductor metal sulfide nanostructures for environmental protection
year: 2018