posted on 2021-05-03, 19:13authored byYimin Liang, Joseph Ka-Ho Hui, Masa-aki Morikawa, Hirotaka Inoue, Teppei Yamada, Nobuo Kimizuka
The
high Seebeck coefficient of an I–/I3– thermocell was achieved by introducing host molecule
PEGylated α-cyclodextrin (TEG-α-CD), which showed thermally
induced phase transition. The host captures I3– at the cold side of the thermocell, which increased Se up to +2.4 mV/K. Notably, the maximum Se value of +4.2 mV/K was observed in the temperature range
between 31 and 37 °C, which was achieved as a consequence of
the phase transition between a hydrophilic phase to a hydrophobic
phase. At the lower temperature side of the thermocell, the host effectively
captures the I3– anion. Meanwhile, microphase
separation of TEG-α-CD occurred at the higher temperature side,
which promoted the dissociation of I3–. This resulted in a large concentration gap of electrochemically
active I3– ions in between the electrodes.
The power density determined for the thermoelectric cell was doubled
in the presence of TEG-α-CD. This result provides a practical
means to design n-type thermocells showing positive Se, only from low-molecular-weight compounds.