Highly efficient solar-thermal-electric conversion based on asymmetric binary-architecture design in solid-solid composite phase change materials

Abstract

The application of phase change materials (PCMs) in solar-thermal conversion is largely limited by the inherently inferior thermal conductivity (TC) and poor solar-thermal energy transition capacity of PCMs. Herein, 1,1,1-tri(hydroxymethyl)ethane@melamine foam/cellulose nanofiber/graphene nanoplate (TME@MCGx) shape-stable composite PCMs (ss-CPCMs) are prepared by encapsulating TME into MCGx aerogels. Profited by the effective heat-conducting MCG25 networks, the resulting TME@MCG25 ss-CPCM achieves high TC of 0.73 Wm-1k−1 for internal heat conduction. Meanwhile, the combination of surface photothermal etching and hydrophobic polydimethylsiloxane (PDMS) coating endows the obtained T-TME@MCG25 highly efficient solar-thermal conversation efficiency of 93.1 %, arising from the exposed 3D MCG25 skeletons for absorbing sunlight and the thin PDMS layer for preventing the absorbed solar-thermal energy from radiating and dissipating. Consequently, the solar-thermal-electric (STE) conversion system equipped with T-TME@MCG25 generates the prominent output voltage of 213.0 mV and current of 37.6 mA. Furthermore, the acquired T-TME@MCG25 exhibits remarkable hydrophobicity and self-cleaning performances, due to the micro-nano structures of MCGx skeleton surfaces and the low surface energy of PDMS coating. The design strategy of asymmetric binary-architecture containing 3D photothermal absorption layer and water repellency layer provides a valuable insight into STE energy conversion associated with hydrophobic ss-CPCMs, which can alleviate the looming energy crisis.