Thermal efficiency of a thermocell made of Prussian blue analogues.

ABSTRACT: Recently, it was reported that a thermocell can convert temperature into electric energy by using the difference in the thermal coefficient (??=?dV/dT) of the redox potential (V) between the cathode and anode materials. Among battery materials, Prussian blue analogues (PBAs) are promising materials for thermocell, because ? changes from approximately -0.3?mV/K in Na_xMn[Fe(CN)₆]_0.83 3.5 H₂O (NMF83) to approximately 1.3?mV/K in Na_xCo[Fe(CN)₆]_0.92,9H₂O (NCF90). In this work, we systematically investigated the thermal efficiency (?) of the NMF83/NCF90 thermocell relative to the difference (?T) between low (T_L?=?282?K) and high (T_H?=?292-338?K) temperatures. We found that the thermal efficiency (?) increased proportionally with ?T. The linear increase in ? is ascribed to the linear increase in the cell voltage (V_cell) and the charge (Q_NCF90) extracted from NCF90. Moreover, ? reached 3.19% at ?T?=?56?K, which corresponds to 19% of the Carnot efficiency (?_carnot?=?17.0%). We further confirmed that the magnitude of Q_NCF90 is quantitatively reproduced by the slopes of the discharge curves of NMF83 and NCF90.

SUBMITTER: Shibata T 

PROVIDER: S-EPMC6170380 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature