A Polymer Nanocomposite with Strong Full‐Spectrum Solar Absorption and Infrared Emission for All‐Day Thermal Energy Management and Conversion

Abstract Realizing efficient energy utilization from the heat source of the sun and the cold source of outer space is of great significance for addressing the global energy and environmental crisis. Materials with ideal full‐spectrum solar absorption and infrared emission are highly desirable for adapting to the continuous weather dynamic throughout the day, nonetheless, their development remains challenging. Here, a polymer nanocomposite with full‐spectrum strong solar (280–2500 nm) absorption ranging from 88.8% to 94.8% with an average value of 93.2% and full‐spectrum high infrared (8–13 µm) emission ranging from 81.3% to 90.0% with an average value of 84.2%, is reported by melt‐processing polypropylene and uniformly dispersed low‐loading MXene nanosheets (1.9 vol%). The nanocomposite can achieve daytime photothermal enhancement of ≈50 °C and nighttime radiative cooling of 8 °C. The temperature difference throughout the day ensures all‐day uninterrupted thermoelectric generation, yielding a power density output of 1.5 W m−2 (daytime) and 7.9 mW m−2 (nighttime) in real outdoor environment without any additional energy consumption. This work provides an impressive polymer nanocomposite with ideal full‐spectrum solar absorption and infrared emission for all‐day uninterrupted thermal energy management and conversion.

parameters, namely: geometry model, weather conditions and internal load.Geometric models include structures and materials.In an energy simulation model, Spaces (such as hot and cold ends) are defined by spatial boundaries.The second input is weather data, including climate parameters such as humidity, wind speed, and outside temperature.Finally, the internal load includes various simulation parameters.
Briefly, a ceramic material is constructed in a space of suitable size as the boundary of the thermoelectric sheet (Figure S10).The upper surface of the thermoelectric sheet is closely bonded to the composite material, and the lower surface is exposed to the environment.The effective area of thermoelectric sheet and composite material is 55×55 mm 2 .The weather data is derived from the 2022 annual weather data file, and the specific locations are selected from the capitals of each country.The thermoelectric sheet (TGM-336-1.4-1.5)contains 241 pairs of semiconductor thermoelectric legs with an average resistance of 2.5 Ω.The other parameters were compared with characterization.
First, the total number of pairs (N T ) of thermoelectric wafer semiconductor modules can be calculated by formula (3): where N S is the number of pairs of series semiconductor modules and N P is the logarithm of parallel semiconductor modules.
The simulated output power can be calculated by formula (4): where P, V and I are power, voltage and current respectively; N T is the total number of semiconductor module pairs calculated in formula (3); S M is the average Seebeck coefficient of the semiconductor module; R M is the average impedance of the semiconductor module; T D is the temperature difference used in the simulation.S13a presents the mechanical properties of the composites, wherein the tensile strength and Young's modulus of the PP/PP-MAH/MXene composite exhibit significant improvements compared to the other components.Specifically, the tensile strength and Young's modulus were measured to be 35.9MPa and 846.1 MPa, respectively, which were 15.9% and 22.9% higher than those of PP matrix.Figure S13b-S13e showcases the cross-sectional SEM images of the composites after undergoing tensile testing.In the PP/MXene composites, the presence of MXene was predominantly observed within the voids generated by material destruction, indicating a weak interaction between MXene and the matrix (Figure S13b and S13c) and making MXene tend to be pulled out under tensile stress.
The addition of a compatibilizer enhances the binding force between the MXene nanosheet and the matrix, thereby enabling MXene to act as a strengthening phase within the matrix (Figure S13d and S13e).Moreover, the droplet phenomenon was significantly mitigated, and the dripping melt no longer sustains combustion.Conversely, the addition of the compatibilizer does not exert a significant influence on the combustion behavior, indicating that the anti-dripping effect was primarily attributed to the presence of MXene.

Figure S9 .
Figure S9.(a) Infrared reflectivity spectrum and (b) infrared transmission spectrum of

Figure
Figure S12.a) Global power generation simulation of different countries.b-g) The monthly

Figure S13 .
Figure S13.(a) Mechanical property of different composites.Cross-section SEM images of

Figure S14 .
Figure S14.Melt droplet resistance property of different composites.Figure S14 illustrates

Figure S15 .
Figure S15.Heat-conducting droplet resistance property of different composites (the infrared

Table S1 .
Detail information of DSC results of different composites.PP PP/MXene PP/PP-MAH/MXene PP/PP-MAH