Contents
1. Introduction Page No.2
2. Development and application of the
thermogalvanic
effect in the field of electrochemistry Page No.3
2.1. Working principle of redox reaction thermocouple Page No.3
2.2. Factors affecting thermocouples based on
thermogalvanic effect Page No.4
2.2.1. Impacts of hydrogel composition Page No.4
2.2.2. Impacts of structure design Page No.6
2.2.3. Impacts of electrode materials Page No.7
2.3. Application aspects and experimental scenarios
of thermogalvanic hydrogels Page No.7
2.3.1. Thermal induction self-supply equipments Page No.7
2.3.2. Integrated applications Page No.8
2.3.3. Heat collection and management devices Page No.9
3. Conclusions and Perspectives Page No.9
1. Introduction
With the exponential increase in energy demand, there has been an
excessive reliance on fossil fuels such as natural gas, oil, and coal,
resulting in severe pollution, widespread environmental damage, and
further aggravation of the global energy
crisis.[1-6] Therefore, the pursuit of energy
recycling has gained significant attention. Heat energy, which is
derived from the burning of fossil fuels or solar radiation, serves as a
widely utilized energy source. While heat can be partially recycled, the
challenge lies in effectively reusing and capturing low-order heat
generated by human activities, solar radiation, and electronic
devices.[7–11]
Solid-state thermoelectric devices based on semiconductors have been
widely researched and applied for the recycling of low-grade thermal
energy. Nonetheless, it is important to acknowledge that the output
performance of these semiconductor devices is temperature-dependent.
Excessively high temperatures pose a risk of fracture in the p-n
junction, resulting in considerable deterioration in performance.
Conversely, extremely low temperatures reduce the thermoelectric
properties of solid materials, resulting in remarkably low Seebeck
coefficients ranging from 100 to 200 µV
K–1.[12,13] Currently,
Bi2Te3 stands as the sole commercially
utilized solid-state material in this domain. [14]Temperature fluctuations threaten the performance stability, safety, and
lifespan of electronics. Thus, maximizing the efficiency of
thermoelectricity and exploring new avenues for its development have
become prominent areas of research. In this context, hydrogels have
emerged as a promising electrolyte medium. Current studies indicate that
hydrogels exhibit two distinct working modes for the thermoelectric
effect: thermogalvanic effect and thermal diffusion effect. Table 1
provides a simple comparison of the two modes. Thermogalvanic effect is
a cost-effective option that offers flexible structural designs. Recent
studies suggest that hydrogels utilizing the thermoelectric current
effect can achieve Seebeck coefficients exceeding 1 mV
K–1.[15–22] Moreover, certain
experimental samples can be coupled and integrated to achieve higher
output voltages. This review primarily focuses on the discussion of
hydrogels using redox reactions as a basis for thermoelectric devices.
It aims to provide a comprehensive understanding of the fundamental
principles, gel structures, and practical applications of such systems.