Intermediate temperature (~400-600^oC) solid oxide fuel cells (IT-SOFC) have drawn growing attention due to the possibility to use cheaper sealing and interconnect materials and the potential to improve system stability and reliability comparing with conventional SOFC that operate at ≥~750^oC. For IT-SOFC, proton conducting oxides such as acceptor-doped Ba(Ce, Zr)O₃ are often preferred over oxide ion conductors as the electrolyte materials due to their high ionic conductivities and low electronic leakage at intermediate temperature. In this study, the electrochemical behaviors of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF), which is one of the most active cathode materials for SOFC and shows significant hydration to become proton conductive in humidified atmosphere, is studied in comparison with other oxide (e.g., Pr₂NiO_4+δ) as well as metal (e.g., Ag) cathode materials at intermediate temperatures of ~350-650^oC. In particular, the influences of different testing conditions including cell configuration (cathode symmetrical cells versus full cells), proton conducting electrolyte thickness, cathodic bias voltage, oxygen concentration, and the presence of air impurities such as water vapor (H₂O) and carbon dioxide (CO₂) on the electrochemical performance are systematically investigated. The implication of the experimental observations especially in terms of the similarity and differences in electrochemical behaviors between different electrode materials to the overall cathode reaction mechanism for proton conducting IT-SOFC is discussed. Finally, the directions for further improving the cathode performance for proton conducting IT-SOFC will be pointed out.