Ikuichiro Izumi

Carbon coating of anatase-type TiO2 and photoactivity

Carbon coating of photocatalytic anatase-type TiO2 powders was successfully carried out by heating a powder mixture of poly(vinyl alcohol) and TiO2 under N2 gas flow at temperatures above 700 °C. All particles of TiO2 were covered by a carbon layer and looked black. For methylene blue (MB) in aqueous solution, carbon-coated anatase powders thus prepared showed marked adsorption and decomposition under UV irradiation and were confirmed to keep almost the same photoactivity as that without any carbon coating. Carbon coating of anatase-type TiO2 was found to give different merits for photoactive performance; suppression of phase transformation from anatase to rutile at high temperatures, quick adsorption of MB into the carbon layer, decomposition of adsorbed MB by TiO2 and prevention of the interaction of TiO2 with binder resin. Repeated cycles of adsorption and decomposition of methylene blue in aqueous solution were experimentally confirmed.

Electrochemical investigation of thin films of cobalt phthalocyanine and cobalt-4,4′,4″,4′″-tetracarboxyphthalocyanine and the reduction of carbon monoxide, formic acid and formaldehyde mediated by the Co(I) complexes

Abstract Cyclic voltammetric investigations of thin films of cobalt(II) phthalocyanine( 1 ) and cobalt(II)-4,4′,4″,4′″-tetracarboxyphthalocyanine( 2 ) in N 2 -saturated 1 M sulfuric acid solution revealed that both compounds gave irreversibly semi-stable reduction products, R- 1 and R- 2 , at around −0.70 V vs sce . Reductions of CO, formaldehyde and formic acid by R- 1 or R- 2 were conducted with vibrating carbon fiber electrode ( cfe ) modified with 1 or 2 . Products of the reduction of CO were mainly formaldehyde and a small amount of methanol. In the reduction of CO, R- 2 / cfe was ca 17 times more efficient than R- 1 / cfe , which was however more efficient than the former in the reduction of formaldehyde. Reduction of formic acid by R- 2 and R- 1 seemed to be difficult under the conditions. Reduction of CO on the 2 / cfe polarized with rectangular potential pulse (−0.659 V for 5s and 0.20 V vs Ag/AgCl for 85s) produced nearly quantitative yield of formaldehyde and small amount of methanol.

Electrochemical intercalation of bromine into graphite in an aqueous electrolyte solution

Abstract By electrochemical oxidation of a graphite sheet in an aqueous solution of potassium bromide, the intercalation of bromine was observed. It was confirmed by the measurements of weight increase of about 10%, decrease in relative electrical resistivity down to 0.69, and enlargement of average interlayer spacing. On the graphite sheet pre-electrolyzed in KBr solution, the chronopotentiogram in K 2 SO 4 aqueous solution showed some plateaux corresponding to the reduction of graphite intercalation compounds with bromine. The longest time on a plateau was observed on the graphite sheet pre-electrolyzed in a potential region of bromine gas evolution, where the most pronounced decrease in electrical resistivity of graphite sheet was detected.

Anodic Oxidation of Acetate and Electroinitiated Polymerization of Acrylic Acid in Glacial Acetic Acid

氷酢酸溶媒中におけるアクリル酸の電解重合を行なった。酢酸-酢酸カリウムの系を電解すると陽極で,通常,Kolbe 反応として知られているようにエタン,二酸化炭素を主として生成し,副生成物としてメタンが生成した。この系にアクリル酸を共存させて電解すると,アクリル酸の重合物が得られた。p-ペンゾキノンによる重合の抑制効果から,アクリル酸の重合開始は,Kolbe反応の中間過程に生成するラジカル種によるものであると考えられた。アクリル酸共存によるKolbe反応生成物の電流効率の低下からアクリル酸濃度1mol/l以上の電解では,電解で生成したアセトキシルラジカルの70%以上がアクリル酸の重合反応に寄与し,残りの30%は脱炭酸してメチルラジカルになり,そのうち75%が重合反応に消費されることがわかった。また,アクリル酸濃度の変化による重合物の収率の変化から,この系における重合反応は不均一表面反応であることが推定された。さらに,電流-電位曲線の解析から,アクリル酸の電極表面への吸着が予想され,重合開始反応にかなり影響しているものと考えられた