Oxygen Reduction Electrode Properties of the Ba(Ce,Gd,Ru)O_(3-δ) Oxides in Alkaline Aqueous Solution

摘要

Two series of compositions, BaCe_(0.8-x)Gd_(0.2)Ru_xO_(3-δ)^s(BCGR_x, x=0-0.8) and BaGd_(1-y)Ru_yO_(3-δ)^s(BGR_y, y=0.5-1,0), were synthesized and their crystal phases were examined. The BCGR_(0.15) and BGR_(0.5) oxides were a single phase of perovskite solid solution, while BCGR_(0.67) and BGR_(0.67) were a perovskite-related superstructure phase. The onset voltage (V_o) of the reduction current and the efficiency (E_4) of the 4-electron reduction of oxygen were evaluated by semi-steady state voltammetry with rotating ring-disk electrodes. In the BCGR_x series, the activities for electrochemical oxygen reduction (EOR) increased with increasing Ru content. In the BGR_y series, the BGR_(0.67) superstructure phase showed a higher EOR activity than the perovskite BGR_(0.5) and the hexagonal(4H) BaRuO_3. This indicates that the EOR activity depends on the crystal phase. The BGR_(0.67) exhibited the best EOR activity of all the samples. The V_o value was 0.80 V vs. reversible hydrogen electrode and the E_4 value was almost 100 %.