High Thermoelectric Performance Sheds New Light for Low-grade Waste Heat Recovery

Recovering waste heat from fuel energy supply is a haunting challenge for greatly reducing the emissions of greenhouse gas CO 2 , and achieving sustainable economy .Importantly, a significant amount of energy is dissipated to environment as low-grade heat (below 250 o C), largely produced in transportation and chemical engineering industry.It accounts for ~30% of the total global energy products but is much more difficult to recycle than high-grade heat (Figure 1 a). 1 So the reuse of low-grade heat is of great importance for the future energy demands and the issue of climate change. 2,3So far, several technologies have been developed to recover low-grade waste heat, such as organic Rankine cycle, water desalination, piezoelectric, and thermoelectric conversion. 4Among them thermoelectric that enables direct and inverse heat-to-electricity conversion is of great interests due to its wide adaptability and long-lasting reliability.However, the low conversion efficiency of thermoelectric power generation limits its potential application in recovering low-grade wasted heat. 5,6e efficiency of thermoelectric power generation is calculated by the unit-less figure of merit, zT=σS 2 T/κ, , where σ, S, κ, and T are the electrical conductivity, Seebeck coefficient, and thermal conductivity of the material, and absolute temperature in kelvin, respectively.To improve the performance, one should expect both a high power factor (σS 2 ), a low thermal conductivity, and material stability with temperature.Unfortunately, the above parameters are entangled, so that it is very difficult to adjust them independently.Traditional methods to decouple this interplay issue is to introduce nanoscale precipitates and regulate the band structure and the