In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2016-02, No. 22 ( 2016-09-01), p. 1649-1649
Abstract:
Introduction Usage of renewable energy has been got a lot of attention to find a way to sustainable society against environment and energy issues. To supply of renewable energy on demand, large-scale of energy storage and transportation is needed. Hydrogen is expected to apply for the energy storage and transportation. We have been paid attention the organic hydride, especially toluene (TL)-methylcyclohexane (MCH) system as a carrier for energy storage and transportation, because it is higher energy density than hydrogen with easy to handle, and can use the petroleum infrastructure in existence. Direct electrohydrogenation of TL applied polymer electrolyte fuel cell and industrial electrolysis technologies is a simple process with high energy conversion efficiency [1-3] . In this process, hydrogen is a byproduct to decrease current efficiency of chemical hydrogen. Therefore, the suppression of hydrogen evolution is needed. In this study, we have investigated the effect of catalyst-loaded backing of electrocatalyst layer on the polarization and the current efficiency with low concentration TL feed to improve cell performance. Experimental Mixture of ethanol, H 2 PtCl 6 ・6H 2 O and H 2 O ( the ratio is 3.0 : 0.3 : 1.0 ) were used as a precursor of Pt catalyst on a carbon paper (35BC, SGL Carbon). The paper was dipped in the mixture, and dried at 60 o C for 10 min. Then it was heated at 240 o C for 6 h in nitrogen atmosphere to prepare Pt loaded cathode backing (called C Pt ). The carbon paper backing with no Pt is called C non-Pt . An anode was the DSE ® (De Nora Permelec Ltd.) electrode for oxygen evolution. A cathode was 0.5 mg cm -2 of PtRu/C (TKK) coated on a C Pt or C non-Pt , and it was hot-pressed(120 o C, 0.27 MPa) on a Nafion ® 117(DuPont). The anode side of the membrane was made hydrophilic before the hot-pressing. Geometrical electrode area was 11.3 cm -2 . 10 ml min -1 of 1 M (=mol dm -3 ) sulfuric acid, and 5 ml min -1 of 10 mol% TL / MCH were circulated to the anode and the cathode compartments, respectively. 10 mol% concentration of TL feed simulates at the vicinity of outlet in a practical electrolyzer. A Luggin capillary for a RHE was placed near the anode. Polarization was evaluated with constant cell voltage measurement for 5 min at 1.3-5.0 V and 60 o C. During the constant cell voltage measurement, the volume of generated hydrogen was determined to evaluate the current efficiency. Resistance of electrolyte evaluated from high frequency intercept in AC impedance at 10 -1 ~10 5 Hz. Results and discussion Figure 1 shows the IR corrected polarization curves with 10 mol% TL feed with C Pt (circular) that was loaded about 0.8 mg cm -2 of Pt and C non-Pt (triangle, diamond). Upper and lower vertical axes are anode and cathode potentials, respectively. Dashed dotted line shows the theoretical potential of 1.23 V and 0.15 V vs. RHE for anode and cathode reaction, respectively. The polarization curves of the anode with the C Pt and C non-Pt were almost the same, while the potential of C non-Pt cathodes were lower than that of C Pt cathode above 300 mA cm -2 of current density region. The former showed diffusion limitation, while the latter did not show. Figure 2 shows the current efficiency (W TL →MCH ) with 10 mol% concentration of TL feed at 60 O C. Side bar shows the fluctuation of current density during constant cell voltage operation. At the low current density below 300 mA cm -2 , the W TL →MCH of the C Pt was significantly higher than that of the C non-Pt . The W TL →MCH of C non-Pt rapidly decreased when the current reached to 400 mA cm -2 , which related to the large change of the cathode potential as shown in Figure 1. In all the current regions, the fluctuation of the C Pt was significantly smaller than that of the C non-Pt . Therefore, the C Pt would promote the catalytic hydrogenation of TL with hydrogen bubble generated as side reaction in cathode. The decrease of hydrogen gas in the backing would lead to improve the TL mass transfer. Acknowledgments This work was supported by Cross-ministerial Strategic Innovation Promotion Program (SIP), “energy carrier” (Funding agency: JST). The Institute of Advanced Sciences (IAS) in Yokohama National University was supported by the MEXT Program for Promoting Reform of National Universities. We appreciate the person concerned them. References K. Ota, A. Ishihara, K. Matsuzawa, and S. Mitsushima, Electrochemistry , 78 , 970 (2010). N. Itou, Hydrogen Energy Systems Society , 33 , 9 (2008). S. Mitsushima, Y. Takakuwa, K. Nagasawa, K. Matsuzawa, Z. Awaludin, A. Kato, Y. Nishiki, Electrocatalysis , 7 , 127 (2016). Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2016-02/22/1649
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2016
detail.hit.zdb_id:
2438749-6
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