Direct urea fuel cells based on CuNi-plated polymer cloth as a anode catalyst
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Research Letter
Direct urea fuel cells based on CuNi-plated polymer cloth as a anode catalyst Keiichi Kaneto , Mao Nishikawa, and Sadahito Uto, Department of Biomedical Engineering, Osaka Institute of Technology, 5-16-1, Ohmiya, Asahi-ku, Osaka, 535-8585, Japan Address all correspondence to Keiichi Kaneto at [email protected] (Received 28 October 2018; accepted 11 December 2018)
Abstract Direct urea fuel cells were fabricated using CuNi-plated polymer cloth for anode catalyst and current collector, and Pt-black for cathode catalyst. The output power was significantly enhanced by coating the CuNi cloth with a conducting polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT*PSS). The open circuit voltage, 0.80 V and the maximum output power, 3.0 mW/cm2 were obtained for the fuel of 0.5 M urea water solution under ambient conditions. Improvement over the cell structure demonstrated to lighten a light emitting diode.
Introduction Urea, which is major component, has been attracted interests for direct and/or microbial fuel cells as a ultimate sustainable and renewable biomass energy source.[1–7] The usefulness of urea was pointed out by Lan and Tao[1] in terms of the volumetric energy density, being about 1.6 times larger than the liquid H2. The issue in direct urea fuel cells is anode catalysts. Pt and rare metals are active to most of biofuels such as glucose and alcohol, however, they are inactive to oxidize urea at the anode. We have studied conducting polymers such as polypyrrole (PPy), polyaniline (PANi), and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT*PSS) to explore potentiality in biosensors[8] and biofuel cells.[9,10] PPy was found to be an excellent mediator to immobilize enzyme of urease to detect urea.[8] PANi and PEDOT*PSS exhibited catalytic activity for biomaterials of ascorbic acid and citric acid.[9,10] Recently, Ni and Co compounds[1,2,5] have been found to be effective catalysts for urea and urine. Direct urea fuel cells[1] with the structure of nano-sized Ni particle for anode and MnO2 for cathode catalysts with anion exchange polymer membrane demonstrated 14.2 mW/cm2 at the maximum power density. Ingenuity upon anion transport membrane and cathode catalyst enhanced the performance to 26.5 mW/cm2 at 300°C.[2] The highest output power reported recently was 33.8 mW/cm2 using anode catalyst, Co3O4NiO and cathode catalyst, Co3O4MnO2 on carbon cloth fibers.[5] We fabricated direct urea fuel cells using CuNi-plated polymer cloth, which played the role of anode catalyst and current collector.[7] CuNi cloth was woven with fine polyester fibers, therefore, resulting in substantially enormous surface area. It was found that the catalytic activity of the CuNi cloth was significantly enhanced by coating with the conducting polymer PEDOT*PSS. The maximum output power was obtained to
be 1.88 mW/m2. This value was not larger than those of the reported values.[1,2,5] However, the CuNi cloth and the membrane are commercially available, and the cells were operated at ambient te
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