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Kaneko M.,Institute of Biophotochemonics Co. | Ueno H.,Institute of Biophotochemonics Co.
Electrochimica Acta | Year: 2013

Efficient direct biomass fuel cell (BMFC) anode/catalysts were successfully prepared that are comprised of [base FTO electrode/mesoporous n-TiO2 thin film/low cost metal thin layer], for which the low cost metal is Co, Ni or Cu, and FTO is a conductive glass electrode coated with an F-doped SnO 2 thin layer. The metal thin layer was reductively electrodeposited onto a mesoporous 10 μm thick TiO2 thin film coated on an FTO. The anode/catalyst semiconductor (SC) devices in which the metal shows metallic luster were efficient for generating electrical power without any photoirradiation nor bias potentials by using polymeric biomass (BM) compounds such as starch, carboxy-methyl cellulose (CMC), and lignin-sulfonic acid in combination with an O2-reducing cathode the other side of which was exposed to ambient air. The TiO2/Cu device anode/catalyst generated with CMC fuel short circuit current Jsc of 740 μA cm-2, open circuit voltage Voc of 0.38 V, and fill factor FF of 0.25, leading to the maximum output power Wout of 70 μW cm-2. The TiO 2/Ni device with starch gave Jsc 870 μA cm-2, Voc 0.33 V, FF 0.24 and Wout 69 μW cm-2. The TiO2/Cu with glucose gave Jsc 850 mA cm-2, Voc 0.69 V, and FF 0.25, attaining Wout 147 μW cm-2. It is important that the capability of electron utilization by the TiO2/Cu device with glucose reached more than 17e- among the theoretical 24e- (=71%) of one glucose molecule. It was strongly suggested that the interface between the TiO2/metal has both the Schottky-junction and Ohmic nature, which interpreted the multi-electron utilization of the biomass. It was proposed that, according to a simple calculation, the device has a potential to be used in a principal sustainable energy resource system. © 2012 Elsevier Ltd. Source


Kaneko M.,Institute of Biophotochemonics Co. | Ueno H.,Institute of Biophotochemonics Co. | Saito R.,Ibaraki University | Nemoto J.,Institute of Biophotochemonics Co.
Catalysis Letters | Year: 2010

UV light-activated highly efficient photocatalytic decomposition of ammonia to N2 in water was successfully achieved by using only a simple mesoporous TiO2 thin film coated on a transparent substrate with external quantum efficiency of 35 (= 3.5 × 103%) based on the total incident UV light. The internal quantum efficiency exceeded 250 (= 2.5 × 104%) in a large scale 22.2 L submodule meaning that ammonia was once activated at TiO2 by UV light the activated ammonia underwent more than 250 times oxidative decomposition by O2 probably via a kind of chain reaction mechanism.© Springer Science+Business Media, LLC 2010. Source


Kaneko M.,Institute of Biophotochemonics Co. | Ueno H.,Institute of Biophotochemonics Co. | Nemoto J.,Institute of Biophotochemonics Co.
Catalysis Letters | Year: 2012

We designed an efficient direct biomass fuel cell (BMFC) anode and prepared a nanocomposite [base electrode/ mesoporous n-semiconductor (SC) thin film/metal thin layer]. A Pt thin layer was photodeposited onto a mesoporous 20-lm thick TiO 2 thin film having a roughness factor of 2000, which was coated on an F-doped tin oxide/ glass base electrode (FTO). This anode/catalyst nanocomposite was efficient at decomposing aqueous solutions of glucose and other biomass-related compounds in combination with an O 2-reducing cathode the other side of which was exposed to ambient air. The nanocomposite exhibited sharp optimum conditions at the atomic ratio of Pt/Ti = 0.33 in the BMFC, generating high electrical power of 2 mW cm -2 without any light irradiation or bias potential when using a 1 M glucose aqueous solution. This output power is 20 times as large as that generated by a mesoporous TiO 2 film anode under UV-light (18 mW cm-2) irradiation. At this ratio, the coated Pt specifically exhibited metallic luster, and its average Pt thickness on the mesoporous TiO 2 nanostructure was calculated to be 0.40 nm. The high BMFC activity was interpreted by the simultaneous Schottky- junction/Ohmic contact nature of the nanocomposite. Other biomass compounds such as sucrose, ethanol and polysaccharides were also effective as direct fuels for the BMFC. Immediately after soaking this composite anode without a cathode in a glucose aqueous solution, continuous evolution of H2 bubbles was observed from the anode surface. The electrical power generation and H2 production are easily changed by connecting and disconnecting a cathode, respectively. Based on a simple design and calculation, the present system with glucose fuel has the potential to construct a module stack of 2 kW m -3. Simultaneous material/ energy circulation by using the BMFC with biomass and its waste fuel is proposed for application in future social systems. © Springer Science+Business Media, LLC 2012. Source


Kaneko M.,Institute of Biophotochemonics Co. | Saito R.,Ibaraki University | Ueno H.,Institute of Biophotochemonics Co. | Nemoto J.,Institute of Biophotochemonics Co. | Izuoka A.,Ibaraki University
Catalysis Letters | Year: 2011

UV light-activated highly efficient photocatalytic decomposition of aqueous glucose and polysaccharides (starch and cellulose) to CO2 was successfully achieved by using a mesoporous TiO2 thin film coated on a fluorine-doped transparent conductive glass (FTO). The external quantum efficiency (η) of 0.08 (=8%) was obtained for glucose photodecomposition at neutral pH based on the total incident UV light, and the internal quantum efficiency (η′) was 8 (=800%) based on the photon that was effective for activating the reactant, demonstrating that the major decomposition mechanism is dark auto-oxidation of the activated reactant by O2. Glucose gave η′ values of 19 at pH 12 and 25 at pH 2 demonstrating that when a glucose molecule was once activated by one photon, the molecule can undergo auto-oxidative decomposition to CO2 at these pH under dark. Water-soluble starch was also photodecomposed completely to CO2 with estimated η′ value of 8.6. Water-soluble carboxymethyl cellulose (CMC) also underwent decomposition to CO2 with similar efficiency of η′ = 5. Solid state cellulose powders could be photodecomposed to CO2 by sandwiching them between FTO-coated TiO2 thin films. © 2011 Springer Science+Business Media, LLC. Source

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