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Enhanced Supply of Hydroxyl Species in CeO2‑Modified Platinum Catalyst Studied by in Situ ATR-FTIR Spectroscopy

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journal contribution
posted on 11.02.2016, 00:00 by Yu Katayama, Takeou Okanishi, Hiroki Muroyama, Toshiaki Matsui, Koichi Eguchi
The recent development of anion exchange membranes (AEMs) has increased the potential of anion exchange membrane fuel cells (AEMFCs). Although highly active electrocatalysts for specific reactions have been successfully developed by placing the most importance on the fuel species, only a few studies have focused on OHad (hydroxyl adsorbed species), which is known to be a common reactive species in alkaline environments. In this study, highly oxophilic CeO2 was selected as a surface modifier for a Pt electrode. We first applied in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to ionomer-coated Pt and CeO2-modified Pt surfaces for clarifying the adsorption behavior of OHad. As a result, a distinct change in adsorption behavior of OHad was confirmed in blank KOH solution. These peculiar characteristics were applicable to various electrochemical oxidation reactions. During the ammonia oxidation reaction, the acceleration of the formation of NOad species was observed in CeO2-modified Pt, suggesting the enhancement of OH adsorption. Furthermore, the degree of activity enhancement by CeO2 addition was investigated for the CO oxidation reaction, methanol oxidation reaction, and ethanol oxidation reaction. Under basic conditions, each of these reactions exhibited distinct activity enhancement. In contrast, under acidic conditions, the promoting effect on these reactions was not observed. These results strongly indicate the potential of our catalyst design strategy and the importance of OHad species as reactive species in alkaline environments.