Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

被引:121
作者
Davis, Danae J. [1 ]
Lambert, Timothy N. [1 ]
Vigil, Julian A. [1 ]
Rodriguez, Mark A. [2 ]
Brumbach, Michael T. [2 ]
Coker, Eric N. [3 ]
Limmer, Steven J. [2 ]
机构
[1] Sandia Natl Labs, Dept Mat Devices & Energy Technol, Albuquerque, NM 87185 USA
[2] Sandia Natl Labs, Albuquerque, NM 87185 USA
[3] Sandia Natl Labs, Adv Mat Lab, Albuquerque, NM 87185 USA
关键词
NANOSTRUCTURED MANGANESE OXIDES; METAL-AIR BATTERIES; ELECTRODE MATERIALS; HYBRID MATERIALS; ALKALINE-MEDIUM; ENERGY-STORAGE; REACTION ORR; FUEL-CELLS; CATALYSTS; GRAPHENE;
D O I
10.1021/jp5039865
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The role of Cu-ion doping in alpha-MnO2 electrocatalysts for the oxygen reduction reaction in alkaline electrolyte was investigated. Cu-doped alpha-MnO2 nanowires (Cu-alpha-MnO2) were prepared with varying amounts (up to similar to 3%) of Cu2+ using a hydrothermal method. The electrocatalytic data indicate that Cu-alpha-MnO2 nanowires have up to 74% higher terminal current densities, 2.5 times enhanced kinetic rate constants, and 66% lower charge transfer resistances that trend with Cu content, exceeding values attained by alpha-MnO2 alone. The observed improvement in catalytic behavior correlates with an increase in Mn3+ content at the surface of the Cu-alpha-MnO2 nanowires. The Mn3+/Mn4+ couple is the mediator for the rate-limiting redox-driven O-2/OH- exchange. O-2 adsorbs via an axial site (the e(g) orbital on the Mn3+ d(4) ion) at the surface or at edge defects of the nanowire, and the increase in covalent nature of the nanowire with Cu-ion doping leads to stabilization of O-2 adsorbates and faster rates of reduction. A smaller crystallite size (roughly half) for Cu-alpha-MnO2 leading to a higher density of (catalytic) edge defect sites was also observed. This work is applicable to other manganese oxide electrocatalysts and shows for the first time there is a correlation for manganese oxides between electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline electrolyte and an increase in Mn3+ character at the surface of the oxide.
引用
收藏
页码:17342 / 17350
页数:9
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