Showing papers by "Akira Fujishima published in 2014"

Bio-Inspired Titanium Dioxide Materials with Special Wettability and Their Applications

Abstract: Their Applications Kesong Liu,†,∥ Moyuan Cao,† Akira Fujishima, and Lei Jiang*,†,‡ †Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing 100191, PR China ‡Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China Research Institute for Science and Technology, Photocatalysis International Research Center, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan Institute for Superconducting and Electronic Materials, University of Wollongong, Innovation Campus, Squires Way, North Wollongong, NSW 2500, Australia

High-yield electrochemical production of formaldehyde from CO2 and seawater.

Abstract: The catalytic, electrocatalytic, or photocatalytic conversion of CO2 into useful chemicals in high yield for industrial applications has so far proven difficult. Herein, we present our work on the electrochemical reduction of CO2 in seawater using a boron-doped diamond (BDD) electrode under ambient conditions to produce formaldehyde. This method overcomes the usual limitation of the low yield of higher-order products, and also reduces the generation of H2 . In comparison with other electrode materials, BDD electrodes have a wide potential window and high electrochemical stability, and, moreover, exhibit very high Faradaic efficiency (74%) for the production of formaldehyde, using either methanol, aqueous NaCl, or seawater as the electrolyte. The high Faradaic efficiency is attributed to the sp(3)-bonded carbon of the BDD. Our results have wide ranging implications for the efficient and cost-effective conversion of CO2.

Superhydrophobic Surfaces Developed by Mimicking Hierarchical Surface Morphology of Lotus Leaf

Abstract: The lotus plant is recognized as a 'King plant' among all the natural water repellent plants due to its excellent non-wettability The superhydrophobic surfaces exhibiting the famous 'Lotus Effect', along with extremely high water contact angle (>150°) and low sliding angle (<10°), have been broadly investigated and extensively applied on variety of substrates for potential self-cleaning and anti-corrosive applications Since 1997, especially after the exploration of the surface micro/nanostructure and chemical composition of the lotus leaves by the two German botanists Barthlott and Neinhuis, many kinds of superhydrophobic surfaces mimicking the lotus leaf-like structure have been widely reported in the literature This review article briefly describes the different wetting properties of the natural superhydrophobic lotus leaves and also provides a comprehensive state-of-the-art discussion on the extensive research carried out in the field of artificial superhydrophobic surfaces which are developed by mimicking the lotus leaf-like dual scale micro/nanostructure This review article could be beneficial for both novice researchers in this area as well as the scientists who are currently working on non-wettable, superhydrophobic surfaces

Thermodynamic and kinetic analysis of heterogeneous photocatalysis for semiconductor systems.

Abstract: Since the report of the Honda–Fujishima effect, heterogeneous photocatalysis has attracted much attention around the world because of its potential energy and environmental applications. Although great progresses have been made in recent years, most were focused on preparing highly-active photocatalysts and investigating visible light utilization. In fact, we are still unclear on the thermodynamic and kinetic nature of photocatalysis to date, which sometimes leads to misunderstandings for experimental results. It is timely to give a review and discussion on the thermodynamics and kinetics of photocatalysis, so as to direct future researches. However, there is an absence of a detailed review on this topic until now. In this article, we tried to review and discuss the thermodynamics and kinetics of photocatalysis. We explained the thermodynamic driving force of photocatalysis, and distinguished the functions of light and heat in photocatalysis. The Langmuir–Hinshelwood kinetic model, the ˙OH oxidation mechanism, and the direct–indirect (D–I) kinetic model were reviewed and compared. Some applications of the D–I model to study photocatalytic kinetics were also discussed. The electron transport mode and its importance in photocatalysis were investigated. Finally, the intrinsic relation between the kinetics and the thermodynamics of photocatalytic reactions was discussed.

Development of sol–gel processed semi-transparent and self-cleaning superhydrophobic coatings

Abstract: Optically transparent, mechanically durable, and self-cleaning superhydrophobic coatings are greatly awaited for applications in daily life. An attempt has been made to develop sol–gel processed semi-transparent, durable and self-cleaning superhydrophobic coatings on glass using a silica–PMMA composite. A water drop acquires a near spherical shape on the coating exhibiting a water contact angle of ∼159° and immediately rolled off under small disturbance. A 10 μl water drop could individually collect around 10 mg of dirt particles along the way whilst rolling off the coating surface. The superhydrophobicity of the coatings remained intact under the impact of a water jet. A water jet hits the superhydrophobic coating and was repelled straightaway off the surface, without leaving any trace of water. These coatings showed both strong superhydrophobicity and superoleophilicity. We observed an improvement in mechanical stability, as well as optical transparency of the coatings in the visible range after low loadings of PMMA polymer (2 vol%) in silica. The prepared coatings maintained excellent superhydrophobicity even after 6 months storage under normal conditions in air.

Synergistic metal-metal oxide nanoparticles supported electrocatalytic graphene for improved photoelectrochemical glucose oxidation.

Abstract: We report the fabrication of graphene–WO3–Au hybrid membranes and evaluate their photocatalytic activity towards glucose oxidase mediated enzymatic glucose oxidation. The dual-functionality of gold nanoparticles in the reinforcement of visible light activity of graphene–WO3 membranes and improving the catalytic activity of immobilized enzymes for unique photoelectrochemical sensing application is demonstrated. This work provides new insights into the fabrication of light-sensitive hybrid materials and facilitates their application in future.

Transparent, Adherent, and Photocatalytic SiO2-TiO2 Coatings on Polycarbonate for Self-Cleaning Applications

Abstract: Photocatalytic TiO2 coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards water and photocatalytic SiO2-TiO2 coatings on polycarbonate (PC) substrate for self-cleaning applications. The silica barrier layer was applied on UV-treated PC substrate before spin coating the SiO2-TiO2 coatings. The effect of different vol% of SiO2 in TiO2 and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail. The coatings prepared from 7 vol% of SiO2 in TiO2 showed smooth, crack-free surface morphology and low surface roughness compared to the coatings prepared from the higher vol% of SiO2 in TiO2. The water drops on this coating acquires a contact angle less than 10° after UV irradiation for 30 min. All the coatings prepared from different vol% (7 to 20) of SiO2 in TiO2 showed high transparency in the visible range.

Simultaneous glucose sensing and biohydrogen evolution from direct photoelectrocatalytic glucose oxidation on robust Cu2O–TiO2 electrodes

Abstract: We report simultaneous photoelectrocatalytic (PEC) glucose sensing and biohydrogen generation for the first time from the direct PEC oxidation of glucose at multifunctional and robust Cu2O–TiO2 photocatalysts. Striking improvement of 30% in overall H2 gas evolution (∼122 μmol h−1 cm−2) by photoholes assisted glucose oxidation opens a new platform in solar-driven PEC biohydrogen generation.

Three-dimensional Gd-doped TiO2 fibrous photoelectrodes for efficient visible light-driven photocatalytic performance

Abstract: To elucidate the influence of electrode geometry on the photocatalytic performance of TiO2, herein, we report the synthesis of three-dimensional in situ Gd-doped TiO2 nanofibers (TiO2-NFs) using a simple electrospinning technique. The as-spun pristine TiO2-NFs show a higher photocatalytic (PC) activity (k = 0.013 m−1) than the TiO2 nanoparticles (TiO2-NPs) (k = 0.006 m−1) electrode, which could be attributed to the fast electron transport in the 1D NFs. In addition, Gd-doped TiO2-NFs show nearly five-fold enhancement in the PC degradation rate due to synergistically higher electron transport and production of HO˙ due to the effects of morphology and doping, respectively. In striking contrast, Gd-doping has no influence on the PC activity of TiO2-NPs due to increased grain boundaries, signifying the vital role of the electrode architecture. The mechanism of Gd doping in pure anatase TiO2 is investigated using density functional theory (DFT) calculations. The influence of Gd-doping and the electrode architecture on the charge recombination and flat-band potential variation in TiO2 are discussed elaborately using ultraviolet photoelectron spectroscopy (UPS) and Mott–Schottky analysis, and the implications of these findings for designing doped 3D fibrous photoelectrodes are discussed.

Enhanced photocatalytic performance at a Au/N–TiO2 hollow nanowire array by a combination of light scattering and reduced recombination

Abstract: We demonstrate one-step gold nanoparticle (AuNP) coating and the surface nitridation of TiO2 nanowires (TiO2-NWs) to amplify visible-light photon reflection. The surface nitridation of TiO2-NW arrays maximizes the anchoring of AuNPs, and the subsequent reduction of the band gap energy from 3.26 eV to 2.69 eV affords visible-light activity. The finite-difference time-domain (FDTD) simulation method clearly exhibits the enhancement in the strengths of localized electric fields between AuNPs and the nanowires, which significantly improves the photocatalytic (PC) performance. Both nitridation and AuNP decoration of TiO2-NWs result in beneficial effects of high (e−/h+) pair separation through healing of the oxygen vacancies. The combined effect of harvesting visible-light photons and reducing recombination in Au/N-doped TiO2-NWs promotes the photocatalytic activity towards degradation of methyl orange to an unprecedented level, ∼4 fold (1.1 × 10−2 min) more than does TiO2-NWs (2.9 × 10−3 min−1). The proposed AuNP decoration of nitridated TiO2-NW surfaces can be applied to a wide range of n-type metal oxides for photoanodes in photocatalytic applications.

Moth-eye-structured Antireflective Poly(methyl methacrylate) Film with Visible-light-responsive Self-cleaning Ability

Abstract: A poly(methyl methacrylate) (PMMA) film with moth-eye-structured surface was coated with PtCl-modified TiO2 (PtCl–TiO2) particles to form an antireflective and self-cleaning film that works under v...