Electrocatalytic activity and stability of Ag-MnO_x/C composites toward oxygen reduction reaction in alkaline solution

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• 作者：Qiumei Wu^a ; ^b ; Luhua Jiang^a ; Luting Qi^a ; Lizhi Yuan^a ; Erdong Wang^a ; Gongquan Sun^a ; ^{gqsun@dicp.ac.cn" class="auth_mail}
• 关键词：Oxygen reduction reaction ; manganese oxide ; silver ; zinc-air battery
• 刊名：Electrochimica Acta
• 出版年：20 March, 2014
• 年：2014
• 卷：123
• 期：Complete
• 页码：167-175
• 全文大小：3168 K

文摘

Ag-MnO_x/C composites were prepared using AgNO₃ and KMnO₄ as the precursors and Vulcan XC-72 as the support. The physical properties of the Ag-MnO_x/C composites were investigated via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The activity and the stability of the series of Ag-MnO_x/C composites toward the oxygen reduction reaction (ORR) in alkaline media were investigated through the electrochemical techniques. The results show that the main species MnO₂ and Ag₂O in the fresh sample convert into Mn₃O₄ and Ag(0), respectively, after the heat treatment in N₂ at 300 掳C (Ag-MnO_x/C-300). The Ag-MnO_x/C-300 sample shows the highest activity toward the ORR, with the half-wave potential of the ORR shifting negatively only 0.035 V compared to that on the commercial 40 wt. % Pt/C (JM). The electron transfer number during the ORR on the Ag-MnO_x/C composite increases with the value close to four after the heat treatment at 300 掳C, which is mainly attributed to the formation of Ag(0), rather than Mn₃O₄. The heat treatment brings about a better catalytic stability of the composite, and no obviously negative shift takes place for the half-wave potential of the ORR on the Ag-MnO_x/C-300 composite after 1000 cycles accelerated aging test. The maximum power density of the zinc-air battery with the Ag-MnO_x/C-300 air electrode reaches up to 130 mW cm^鈭?, higher than those based on the Pd/C and Pt/C cathode catalysts, which shows that the Ag-MnO_x/C-300 composite is a promising candidate as the catalyst for the air electrode.