High-valence-state manganate(V) Ba3Mn2O8 as an efficient anode of a proton-conducting solid oxide steam electrolyzer
High-valence-state manganate(V) Ba3Mn2O8 as an efficient anode of a proton-conducting solid oxide steam electrolyzer
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高价态锰酸盐（V）Ba3Mn2O8作为质子传导固体氧化物蒸汽电解槽的高效阳极
DOI：
10.1039/c9qi00253g
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Hiroki Habazaki and Yoshitaka Aoki
中科院分区：
文献类型：
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作者：
Hajime Toriumi;Taisei Kobayashi;Satoshi Hinokuma;Toshiaki Ina;Takashi Nakamura;Koji Amezawa;Chunyu Zhu;Hiroki Habazaki and Yoshitaka Aoki
本文研究了高价态锰(V)氧化物Ba3(MnO4)2作为H+导电固体氧化物蒸汽电解槽(H-SOEC)的阳极电催化剂。Ba3(MnO4)2由C3v对称的MnO43−氧阴离子组成，在室温下有三个长的Mn-O键和一个短的Mn-O键。Ba3(MnO4)2由于反铁磁/顺磁相变导致电导率跃升一个数量级，同时伴随着四面体MnO43−阴离子从C3v到Td对称性的形状变化，电导率测量和高温下扩展的X射线吸收精细结构证实了这一点。因此，H-SOEC的Ba3(MnO4)2基阳极具有更好的性能，阳极极化电阻低于著名的H-SOEC阳极材料Sm0.5Sr0.5CoO_3。氧分压和水分压的阻抗分析表明，Ba3(MnO4)2基阳极性能的优越归因于反应面积的扩大。由于高价态Mn5+离子丰富的空位3d态有利于与水电子给体的电荷转移相互作用，从而有利于水的吸附，因此析氧反应可以直接发生在电极表面，因此反应位置不局限于气体-电极-电解液三相界面。
Herein, high-valence-state Mn(V) oxide, barium manganate(V) (Ba3(MnO4)2), is examined as an anode electrocatalyst of a H+-conducting solid oxide steam electrolysis cell (H-SOEC). Ba3(MnO4)2 comprises C3v-symmetric MnO43− oxo-anions with three long Mn–O bonds and one short Mn–O bond at room temperature. Ba3(MnO4)2 caused a conductivity jump by one order of magnitude at approximately 600 °C owing to the antiferromagnetic/paramagnetic phase transition, accompanied by a shape change of the tetrahedral MnO43− anions from C3v to Td symmetry, as confirmed by the electrical conductivity measurements and the extended X-ray absorption fine structure at an elevated temperature. Hence, the Ba3(MnO4)2 base anode of the H-SOEC exhibited improved performance, with anode polarization resistances being lower than those of Sm0.5Sr0.5CoO3, a well-known H-SOEC anode material. Impedance analysis in terms of oxygen and water partial pressure revealed that the superior performance of the Ba3(MnO4)2 base anode can be attributed to the extended reaction area. Since abundant unoccupied 3d states of the high-valence-state Mn5+ cations are favorable for charge transfer interactions with water electron donors, thereby facilitating water adsorption, the oxygen evolution reaction could occur directly over the electrode surface, and thus the reaction sites were not limited to the gas–electrode–electrolyte triple phase boundary.