Prussian Blue Analogues as Promising Thermal Power Generation Materials

The thermal coefficient ( α =d V /d T ) of redox potential ( V ) enables an efficient thermal power generation using waste heat. Actually, a battery‐type thermocell, which consists of two kinds of redoxable solids with different α as anode and cathode, is demonstrated to produce electric energy in thermal cycles. To fabricate high performance device, α is systematically investigated in three kinds of Prussian blue analogues (PBAs), Na x Co[Fe(CN) 6 ] 0.71 (abbreviated as NCF71), Na x Co[Fe(CN) 6 ] 0.90 (NCF90) and Na x Mn[Fe(CN) 6 ] 0.83 (NMF83), against the Na + concentration ( x ). NCF90 shows the highest positive α (=1.4 mV K −1 ) in the lower‐lying plateau while NMF83 shows the highest negative α (=−0.4 mV K −1 ) in the lower‐lying plateau. In addition, the NCF90/NMF83 thermocell produces 5.5 meV/NCF90 in the initial cycle between T L (=286 K) and T H (=313 K). The thermal efficiency ( η =2.3 %) reaches 27 % of the Carnot efficiency ( η carnot =8.7 %). Thus, PBAs are promising materials for thermal power generation.