Composite Photocatalysts Nan Zhang,†,‡ Min-Quan Yang,†,‡ Siqi Liu,†,‡ Yugang Sun,* and Yi-Jun Xu*,†,‡ †State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou 350002, P.R. China ‡College of Chemistry, New Campus, Fuzhou University, Fuzhou 350108, P.R. China Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States

Waltzing with the Versatile Platform of Graphene to Synthesize Composite Photocatalysts.

In the present review we try to give a comprehensive and most up to date view to the field, with an emphasis on the currently most investigated anodic TiO2 nanotube arrays. We will first give an overview of different synthesis approaches to produce TiO2 nanotubes and TiO2 nanotube arrays, and then deal with physical and chemical properties of TiO2 nanotubes and techniques to modify them. Finally, we will provide an overview of the most explored and prospective applications of nanotubular TiO2.

One-dimensional titanium dioxide nanomaterials: nanotubes.

Titanium dioxide (TiO2) has been the most intensively investigated binary transition metal oxide in the past four decades as indicated by Figure S1. Furthermore, the annual number of papers published on TiO2 has seen a continuous increase, particularly since the beginning of this century (Figure S2). This is understandable when one considers the wide range of applications of TiO2 from the conventional areas (i.e., pigment, cosmetic, toothpaste, and paint) to the later developed functional areas such as photoelectrochemical cell,(1-3) dye-sensitized solar cells (DSSCs),(4-11) photocatalysis,(12-24) catalysis,(25-31) photovoltaic cell,(32-34) lithium ion batteries,(35-41) sensors,(42-46) electron field emission,(47-51) microwave absorbing material, biomimetic growth, and biomedical treatments.(52-57) Nearly all these functional applications of TiO2 fall in the scope of energy, environment, and health, which are definitely the three most important and challenging themes facing the Human race that need to be addressed in this century. Besides the apparent merits including nontoxicity, elemental abundance, good chemical stability, and easy synthesis, TiO2 has attracted strong research interest worldwide due to its physicochemical properties for realizing various functions.(15, 58, 59) Especially, very encouraging progresses in photocatalysis and DSSCs with the involvement of TiO2 have greatly stimulated the rapid development of TiO2 crystals with controllable phase, size, shape, defect, and heteroatom.(58, 60-68)

Titanium dioxide crystals with tailored facets

The design and development of efficient TiO 2 -based, hybrid, nanostructured photocatalysts has recently been receiving substantial attention for environmental remediation due to their excellent physiochemical properties. This article provides an overview of the synthesis strategies and characteristics of the next-generation TiO 2 -based hybrid photocatalysts, produced in combination with polymers (e.g., polyaniline, polypyrrole, polythiophene) and carbon nanomaterials (e.g., graphene, GO, CNT, carbon quantum dots, carbon nitride). The structural aspects, nanostructure formation process, parameters affecting catalytic activity, photocatalytic mechanisms and photocatalytic applications of TiO 2 -based catalysts for efficient photocatalytic degradation of gaseous/volatile organic pollutants in water/air are reviewed. Further, current research trends, means to increase catalytic performance and future prospects of high-performance TiO 2 -based hybrid photocatalytic materials, are briefly summarized.

Hybrid nanostructures based on titanium dioxide for enhanced photocatalysis

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.

Applied photoelectrocatalysis on the degradation of organic pollutants in wastewaters

Preparation of graphene film decorated TiO2 nano-tube array photoelectrode and its enhanced visible light photocatalytic mechanism

Preparation and characterization of palladium nano-crystallite decorated TiO2 nano-tubes photoelectrode and its enhanced photocatalytic efficiency for degradation of diclofenac

Junjing Li

Papers

Preparation of graphene film decorated TiO2 nano-tube array photoelectrode and its enhanced visible light photocatalytic mechanism

Preparation and characterization of palladium nano-crystallite decorated TiO2 nano-tubes photoelectrode and its enhanced photocatalytic efficiency for degradation of diclofenac

Investigation on electrochemical properties of cerium doped lead dioxide anode and application for elimination of nitrophenol

Construction of N, S codoped TiO2 NCs decorated TiO2 nano-tube array photoelectrode and its enhanced visible light photocatalytic mechanism

Reuse of sewage sludge as a catalyst in ozonation--efficiency for the removal of oxalic acid and the control of bromate formation.