Preparation And Application Of Carbon Dots/TiO₂Nanotube Arrays

Nowadays, the presence of emerging unbiodegradable organic pollutants in theaquatic environment has been catched much attention. The application ofphotocatalytic or photo-electrocatalytic processes using a new TiO₂nanostructurecomposite to alternate the conventional treatment methods. However, the TiO₂bandedge is broad and the rapid recombination of e/h+photogenerated, that makes theminactive under visible irradiation. To ensure higher efficiency of photocatalyticprocess, we coupling TiO₂with carbon dots（CDs）， a new class of carbonnano-materials with sizes below10nm, which has been proved to act an attractiveoptical property—upconversion photoluminescence（UCPL）. The mainly works arelisted as follows：（1）Highly Efficient Photoelectrocatalytic Oxidation of Methanol under VisibleLight on Pt/Ru Nonoparticles Modified Self-assembly CDs/TiO₂Nanotube Arrays.First, TiO₂NTs were prepared by anodizing titanium process, then the TiO₂NTs wereself-assembled by CDs and midified by RuPt with electroless plating technology. Inthis work, carbon dots （CDs） were prepared by anodizing graphite rod in KH2PO4solution. The CDs with surface groups such as–COO-and–OH were covered byhydrogen ions through electrostatic attraction. Consequently, the CDs with a positivecharge shell can be driven toward the cathode, anodic TiO₂NTs/Ti, by electric fieldpower through a self-assembly method. Since the top surface of the TiO₂nanotubearrays is a porous interface, the CDs can be tightly attached onto the nanotubes. Theresulting CDs/TiO₂ribbon was then taken as a substrate to load Pt Ru nanoparticlesby electrodeposition, constructing an integrated, hybrid and optoelectronic material inhighly catalyzing methanol under visible light. The high catalytic efficiency can beattributed to the sensitivity to the visible light and fast electron-transfer property of theCDs layer. PtRu/CDs（6h）/TiO₂NTs shows the maximal Ipfof542.36mA·cm^-2（mg Pt）-1which is twice that of261.80mA·cm^-2（mg Pt）-1on the PtRu/TiO₂NTs. With CDsloaded on the PtRu/TiO₂NTs electrode, the current density is about9times thatdetected on PtRu/TiO₂NTs（2） In this work a novel CDs/Cu₂O/TiO₂NTs composite photocatalyst undervisble light was successfully. This composite has an efficient photocatalytic activity based on the up-converted PL property of CDs and the heterojunction networkstructure of the Cu₂O/TiO₂NTs. As we kown, UV light only accounts for4%ofsunlight, so visble light sensitive photocatalysts will be a key factor in photocatalysis.We therefore expect that our findings will significantly push research in currentenvironmental pollution, energy issues and other related areas.（3） The N/TiO₂NTs were surface functionalizated by hydrophobic CDs throughamide linkages formed by polymerizing citric acid and octadecylamine in a situ way.The senior alkane chains were linked on the carbon dots core, and formedhydrophobic corona. Different ID/IGCDs was got during our Raman spectra, byelevated temperature condensation of the ammonium carboxyl groups （NH3+OOCâ†'NHCO+H₂O）. The ratio of hydrophilic and hydrophobic was also regulated bythe surfactant and the carbon souce. The as-obtained CDs/N/TiO₂NTs, synthesized byan easy, low-cost, green and one-step pyrolytic method, were successfully preparedfor selective photocatalytic hydrophobic organics.