Harnessing waste energy through carbon dioxide-induced thermally regenerative electrochemical cells

Abstract

Energy and environmental concerns are two critical challenges facing the world in the 21st century. A vital strategy to overcome these challenges and pave the way to a sustainable future involves regenerating energy from waste resources. This dissertation explores the potential of CO2-induced thermally regenerative electrochemical cells (cTRC) as an innovative approach to harness waste CO2 and low-grade heat for electricity generation. The research delves into the mechanics, working principles, and performance optimization of cTRC systems. Through a comprehensive analysis of the cTRC technology, including its mass and energy cycle, and its physical components, the design principle is established and verified with a Mn-cTRC model. This model demonstrates the capability to generate electrochemical energy through CO2 and heat input. Experimental results confirm the feasibility of cTRC, achieving a CO2-induced voltage of approximately 180 mV and a power density of 0.58 W m-2. A regeneration process is completed after 30 cycles at 90℃. Mn-cTRC showcases the potential for practical applications. Next, a more advanced design, the Ni@Co-cTRC is introduced, utilizing electrochemical methods to fabricate Ni@Co double-layered porous active materials on carbon fibers. A CO2-induced voltage of approximately 230 mV is observed, with the maximum power density reaching 3.95 W m-2, which is a significant improvement compared with the previous system. The potential for future applications, such as small electronics, is showcased by connecting a series of Ni@Co-cTRCs to produce a voltage of 1.5 V and powered a smart window. Nevertheless, the discharging time in a single cycle remains limited, primarily due to the small loading of active materials. Therefore, an H2-cTRC is presented, employing gas electrodes to overcome electrode capacity limitations, achieving an exceptionally long discharging time and a power density of 5.30 W m-2. Proof-of-concept implementation successfully powered a smartphone, paving the way for practical waste- to-electricity conversion applications. In conclusion, cTRCs are shown to be an effective and promising solution for capturing and utilizing waste CO2 and low-grade heat to generate electricity. Through systematic optimization, the experimental energy output was pushed close to theoretical predictions. These findings contribute to the development of sustainable energy systems and provide a solid foundation for future work on cTRCs and their large-scale implementation. By addressing critical aspects such as design strategy, in-depth mechanisms, and system optimization, this research advances the field of waste-to-electricity conversion and offers valuable insights for continued innovation.