TY - JOUR
T1 - Synthesis of Type II Ge and Ge-Si Alloyed Clathrates Using Solid-State Electrochemical Oxidation of Zintl Phase Precursors
AU - Dopilka, Andrew
AU - Ovchinnikov, Alexander
AU - Childs, Amanda
AU - Bobev, Svilen
AU - Peng, Xihong
AU - Chan, Candace K.
N1 - Publisher Copyright:
© 2022 American Chemical Society.
PY - 2022/8/8
Y1 - 2022/8/8
N2 - Germanium clathrates with the type II structure are open-framework materials that show promise for various applications, but the difficulty of achieving phase-pure products via traditional synthesis routes has hindered their development. Herein, we demonstrate the synthesis of type II Ge clathrates in a two-electrode electrochemical cell using Na4Ge4-ySiy (y = 0, 1) Zintl phase precursors as the working electrode, Na metal as the counter/reference electrode, and Na-ion conducting β″-alumina as the solid electrolyte. The galvanostatic oxidation of Na4Ge4 resulted in voltage plateaus around 0.34-0.40 V vs Na/Na+ with the formation of different products depending on the reaction temperature. When using Na4Ge3Si as a precursor, nearly phase-pure, alloyed type II Ge-Si clathrate was obtained at 350 °C. The Na atoms in the large (Ge,Si)28 cages of the clathrate occupied off-centered positions according to Rietveld refinement and density functional theory calculations. The results indicate that electrochemical oxidation of Zintl phase precursors is a promising pathway for synthesizing Ge clathrates with type II structure and that Si alloying of the Zintl phase precursor can promote selective clathrate product formation over other phases.
AB - Germanium clathrates with the type II structure are open-framework materials that show promise for various applications, but the difficulty of achieving phase-pure products via traditional synthesis routes has hindered their development. Herein, we demonstrate the synthesis of type II Ge clathrates in a two-electrode electrochemical cell using Na4Ge4-ySiy (y = 0, 1) Zintl phase precursors as the working electrode, Na metal as the counter/reference electrode, and Na-ion conducting β″-alumina as the solid electrolyte. The galvanostatic oxidation of Na4Ge4 resulted in voltage plateaus around 0.34-0.40 V vs Na/Na+ with the formation of different products depending on the reaction temperature. When using Na4Ge3Si as a precursor, nearly phase-pure, alloyed type II Ge-Si clathrate was obtained at 350 °C. The Na atoms in the large (Ge,Si)28 cages of the clathrate occupied off-centered positions according to Rietveld refinement and density functional theory calculations. The results indicate that electrochemical oxidation of Zintl phase precursors is a promising pathway for synthesizing Ge clathrates with type II structure and that Si alloying of the Zintl phase precursor can promote selective clathrate product formation over other phases.
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U2 - 10.1021/acs.inorgchem.2c01748
DO - 10.1021/acs.inorgchem.2c01748
M3 - Article
C2 - 35876805
AN - SCOPUS:85135896952
SN - 0020-1669
VL - 61
SP - 12363
EP - 12372
JO - Inorganic chemistry
JF - Inorganic chemistry
IS - 31
ER -