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The oxygen reduction reaction (ORR) has been studied on low-index planes of Pd in 0.05 M XOH (X = Li, Na, K, and Cs) solutions to determine the effects of cations on ORR activity. The order of ORR activity is Pd(110) ＜ Pd(100) ＜ Pd(111) in all solutions. This order differs from that in HClO4: Pd(110) ＜ Pd(111) ≪ Pd(100). Cationic species do not affect the ORR activity on Pd(110) and Pd(100). In contrast, the ORR activity of Pd(111) increases in the order of Li+ ＜ Na+ ＜ K+ ＜ Cs+. The lower the cation hydration energy, the higher the ORR activity on Pd(111), as is also the case on Pt(111). The ORR activity of Pd(111) in CsOH is 1.8 times higher than that of Pd(100) in HClO4.