ステップ構造を有する白金およびパラジウム触媒上での燃料電池反応

抄録

Structural effects on the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) have been studied on the high index planes of Pt and Pd in 0.1 M HClO₄. The exchange current density j_o of the HOR increases with the increase of the step atom density d_S from n = ∞ to 9 on(n−1)(111)-(110), n(111)-(100), n(100)-(111) and n(100)-(110) surfaces of Pt, where n shows the number of the terrace atomic rows. On the surfaces with n ≤ 9, however, the values of j₀ do not depend on d_S. These facts support that the step is the active site for the HOR on Pt electrodes, however, only part of the step atoms contributes to the HOR. Pt electrodes of (n−1)(111)-(110) series have the highest activity for the HOR. The activity for the ORR increases with the increase of the terrace atom density d_T on Pd electrodes. The step atoms do not affect the ORR. Pd(100) has the highest activity for the ORR. The specific activity of Pd(100) is 4.2 times as high as that of the standard Pt catalyst (TEC10E50E). The mass activity of Pd surfaces covered with monolayer of Pt (Pt/Pd(hkl)) is 7 times as high as that of TEC10E50E.