TY - JOUR
T1 - High-valence-state manganate(v) Ba3Mn2O8 as an efficient anode of a proton-conducting solid oxide steam electrolyzer
AU - Toriumi, Hajime
AU - Kobayashi, Taisei
AU - Hinokuma, Satoshi
AU - Ina, Toshiaki
AU - Nakamura, Takashi
AU - Amezawa, Koji
AU - Zhu, Chunyu
AU - Habazaki, Hiroki
AU - Aoki, Yoshitaka
N1 - Funding Information:
This work was supported by the JST MIRAI “Realization of a low carbon society, global issue”, No. JPMJM17E7; the JSPS KAKENHI: Grant-in-Aid for Scientific Research (B), No. 18H02066; and the “Nanotechnology Platform” program of the MEXT Japan. XAFS measurements were performed with the approval of SPring-8 (No. 2017B1288).
Publisher Copyright:
© 2019 the Partner Organisations.
PY - 2019/6
Y1 - 2019/6
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85067262390&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85067262390&partnerID=8YFLogxK
U2 - 10.1039/c9qi00253g
DO - 10.1039/c9qi00253g
M3 - Article
AN - SCOPUS:85067262390
SN - 2052-1545
VL - 6
SP - 1587
EP - 1597
JO - Inorganic Chemistry Frontiers
JF - Inorganic Chemistry Frontiers
IS - 6
ER -