Chiaki Terashima

High‐Yield Electrochemical Production of Formaldehyde from CO2 and Seawater

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.

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

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.

Superhydrophobic surfaces developed by mimicking hierarchical surface morphology of lotus leaf.

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.

A mechanically bendable superhydrophobic steel surface with self-cleaning and corrosion-resistant properties

We present an effective way to develop superhydrophobic steel surface which shows stable superhydrophobicity under harsh mechanical bending. The roughness on the steel surface was created by etching in acid solution and its surface energy was lowered by subsequent hydrophobic silane treatment. The steel etching time in sulfuric acid solution was optimized to 8 h which provides high surface roughness required for superhydrophobicity. A water contact angle of 164 ± 3° and a sliding angle of 9 ± 2° were obtained for the steel surface after surface chemical modification by methyltrichlorosilane. We bent this superhydrophobic steel to 90° and 180° and studied the wetting properties on the bent area, which showed absolutely no change in superhydrophobicity. This superhydrophobic steel surface showed excellent self-cleaning behaviour as well as maintained its superhydrophobic wetting properties under a stream of water jet. Further, the stability of the wetting state was evaluated using a sandpaper abrasion test, adhesive tape peeling test, and under prolonged UV irradiation. Energy-dispersive X-ray spectroscopy was used to confirm the surface chemical composition of the superhydrophobic steel surface. This approach can be applied to steel surfaces of any size and shape to advance their industrial applications.

Electrochemical Behavior of Cobalt Oxide Films Deposited at Conductive Diamond Electrodes

Department of Chemistry and Center for Integrated Molecular Systems, Pohang University of Scienceand Technology, Pohang 790-784, South KoreaThe oxidation of Co~II! at a boron-doped diamond~BDD! electrode was investigated by use of anodic voltammetry. The resultsshows that this reaction takes place by a mechanism similar to that of cobalt metal oxidation in alkaline media. The voltammetriccurves evidence a strong enhancement of the oxygen evolution current in the presence of Co~II!. This behavior is consistent withcobalt oxide formation at the diamond electrode surface. Based upon these results, a simple, straightforward method for theproduction of high activity films on BDD electrode surfaces is demonstrated. The study of the electrochemical behavior in 1 MNaOH shows that the electrodes thus obtained exhibit promising, stable electrocatalytic performance for oxygen evolution,comparing well with those of thermally deposited cobalt electrodes. The use of BDD as a substrate for the electrocatalytic layersallows the deposition of isolated particles or discontinuous films, thus maximizing the utilization of the catalyst by avoiding theneed for thick films.© 2003 The Electrochemical Society. @DOI: 10.1149/1.1579037# All rights reserved.Manuscript submitted September 6, 2002; revised manuscript received February 3, 2003. Available electronically May 16, 2003.

Electrodeposition of hydrous iridium oxide on conductive diamond electrodes for catalytic sensor applications

Abstract Boron-doped diamond (BDD) electrodes have been modified by hydrous iridium oxide (IrO x ) electrodeposition, and depending on the deposition conditions, either highly dispersed iridium oxide nanoparticles or continuous oxide films were obtained. The electrochemical characteristics of IrO x on BDD compare well with those obtained on other substrate materials. The proposed method allows excellent control of the deposited amount, and high reproducibility of the electrochemical performance. Electrodes obtained by the deposition of a very low amount of IrO x (ca. 2 nmol cm −2 ) on the diamond surface exhibited an excellent analytical performance for hydrogen peroxide amperometric detection, that compares favorably with those obtained by using other substrate materials. Furthermore, these electrodes enabled H 2 O 2 detection in neutral media, which is an advantage compared to sensors obtained by iridium oxide deposition on other substrates. The detection limit for H 2 O 2 was ca. 10 times lower than that of commercially available platinum bulk electrodes. By proper selection of the diamond substrate structure, continuous IrO x layers of different thickness were formed. The IrO x /BDD electrodes have also exhibited excellent pH-sensing properties in a wide pH range, and high stability of the potentiometric response. These studies indicated that, by proper selection of the diamond substrate structure, robust IrO x layers could be prepared for use as H 2 O 2 detection and pH sensors.

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

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.

Self-cleaning and superhydrophobic CuO coating by jet-nebulizer spray pyrolysis technique

We demonstrate for the first time the fabrication of a superhydrophobic CuO coating with excellent self-cleaning ability by a custom-made jet nebulizer spray pyrolysis technique. A stable Cassie–Baxter superhydrophobic wetting state (water contact angle, ~154°) was maintained even after high speed water jet impact on a monoclinic CuO crystallite coating, which realizes the robust feature of coating. The mist-type aerosol distribution from the nebulizer controls the resultant morphology of the CuO film, thereby tuning the superhydrophobic properties. The low-cost (~

Electrochemical glucose detection using nickel-implanted boron-doped diamond electrodes

1) portable pocket-sized nebulizer affords reliable CuO superhydrophobic coatings on a wide range of desired host surfaces.

Fabrication of vertically aligned diamond whiskers from highly boron-doped diamond by oxygen plasma etching.

Nickel-implanted boron-doped diamond electrodes (Ni-DlA) were fabricated in view of their application for carbohydrate detection. This electrode produced well-defined and reproducible voltammograms for 1 mM glucose in alkaline media. The electrode exhibited excellent electrochemical stability with low background current even after ultrasonic treatment, indicating the strong bonding of nickel with carbon. These results indicate the promising use of Ni-DIA for the detection of carbohydrates and amino acids, and thus, an application of ion implantation as the surface modification method is effective for controlling the electrochemical properties of polycrystalline diamond thin films.