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Efficient Low‐Grade Heat Harvesting Enabled by Tuning the Hydration Entropy in an Electrochemical System
Author(s) -
Gao Caitian,
Liu Yezhou,
Chen Bingbing,
Yun Jeonghun,
Feng Erxi,
Kim Yeongae,
Kim Moobum,
Choi Ahreum,
Lee HyunWook,
Lee Seok Woo
Publication year - 2021
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202004717
Subject(s) - carnot cycle , materials science , electrochemistry , intercalation (chemistry) , thermodynamics , entropy (arrow of time) , electrochemical cell , coefficient of performance , electrode , heat pump , chemistry , heat exchanger , inorganic chemistry , physics
Harvesting of low‐grade heat (<100 °C) is promising, but its application is hampered by a lack of efficient and low‐cost systems. The thermally regenerative electrochemical cycle (TREC) is a potential alternative system with high energy‐conversion efficiency. Here, the temperature coefficient (α), which is a key factor in a TREC, is studied by tuning the hydration entropy of the electrochemical reaction. The change of α in copper hexacyanoferrate (CuHCFe) with intercalation of different monovalent cations (Na + , K + , Rb + , and Cs + ) and a larger α value of −1.004 mV K −1 being found in the Rb + system are observed. With a view to practical application, a full cell is constructed for low‐grade heat harvesting. The resultant η e is 4.34% when TREC operates between 10 and 50 °C, which further reaches 6.21% when 50% heat recuperation is considered. This efficiency equals to 50% of the Carnot efficiency, which is thought to be the highest η e reported for low‐grade heat harvesting systems. This study provides a fundamental understanding of the mechanisms governing the TREC, and the demonstrated efficient system paves the way for low‐grade heat harvesting.