Science - USA (2020-06-05)

From the Onsager transport formulation, we
see how a large, positive thermopower comes
from the coupling of the thermodiffusion and
thermogalvanic effects ( 33 ). We observed that
the total thermopowerSicould be written as
a summation:

Si=–aR+Std(K+–FeCN^4 – /3–)+

Std(KCl) +Std(gelatin) (2)

where–aRis the contribution to thermo-

power from the redox reaction FeCN^3 – +e⇋

FeCN^4 – ,Stdis the thermopower from the

thermodiffusion of mobile ions, andStd(gelatin)

is the intrinsic thermopower of the gelatin.

We used an isothermal three-electrode sys-

tem (Fig. 2D) to effectively eliminate theT

gradient and determine the temperature co-

efficient ( 33 ). The contribution from the redox

Hanet al.,Science 368 , 1091–1098 (2020) 5 June 2020 4of7

Fig. 2. Mechanism of the synergistic effect.Electrochemical potential (~m)
of charge carries diagrams and the corresponding voltage (V) distribution of
i-TE material of Gelatin-xKCl-m/nFeCN^4 – /3–as (A)Gelatin-KCl(x=0.8M,
m/n=0M),whereErepresents the built-in electric field; (B) Gelatin-FeCN^4 – /3–
(x=0M,m/n= 0.42/0.25 M); and (C) Gelatin-0.8 M KCl-0.42/0.25 M
FeCN^4 – /3–.(D) Isothermal system of Gelatin-FeCN^4 – /3–for measuring the
entropy of FeCN^4 – /3–. The work electrode (WE) was platinum, whereas SCE

was used as the reference electrode(RE) and counter electrode (CE). (E)Thermo-

power caused by redox entropy change of FeCN^4 – /3–(−aR) measured from

(D) and total value (Si). (F) Schematic figure of the diffusion, redox reaction,

and interaction of the ions in the as-fabricated i-TE materials of Gelatin-x

KCl-m/nFeCN^4 – /3–under the temperature gradient. (G) Fractional contribution

to thermopower of i-TE material Gelatin-0.8 M KCl-0.42/0.25 M FeCN^4 – /3–

(rv=2.0).

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