Engineering the electrochemical temperature coefficient for efficient low-grade heat harvesting

• Main Authors: Gao, Caitian, Yin, Yuling, Zheng, Lu, Liu, Yezhou, Sim, Soojin, He, Yongmin, Zhu, Chao, Liu, Zheng, Lee, Hyun-Wook, Yuan, Qinghong, Lee, Seok Woo
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Electrical and electronic engineering; Electrochemical Temperature Coefficients; Lattice Parameters
• Online Access: https://hdl.handle.net/10356/140294
• Institution: Nanyang Technological University

Low-grade heat to electricity conversion has shown a large potential for sustainable energy supply. Recently, the low-grade heat harvesting in the thermally regenerative electrochemical cycle (TREC) is a promising candidate with high energy conversion efficiency. In this system, the electrochemical temperature coefficient (α) plays a dominant role in efficient heat harvesting. However, the internal factors that affect α are still not clear and significant improvements are needed. Here, α of various Prussian Blue analogues (PBAs) is investigated and their lattice change during cation intercalation is monitored using the ex situ X-ray diffraction (XRD) method. For the first time, it is found that α is highly related to the lattice parameter change. Large lattice shrinkage exhibits a large negative α, while lattice expansion is corresponding to a positive α. These are mainly attributed to the different phonon vibration entropy changes upon cation intercalation in various PBAs. Especially, purple cobalt hexacynoferrate delivers the largest α of −0.89 mV K−1 and enables highly efficient heat conversion efficiency up to 2.65% (21% of relative efficiency). The results of this study provide a fundamental understanding of temperature coefficient in electrochemical reactions and pave the way for designing high-performance material for low-grade heat harvesting.