Controllable fabrication and characterization of porous C/TiO2 nanocomposite films as solar selective absorber

Porous C-TiO2 nanocomposite films prepared by photopolymerization-induced phase-separation method (PIPS) exhibited three dimensional interconnected pores structure. Scanning electron microscopy (SEM), atomic force microscope (AFM), thermo-gravimetric and differential thermal analysis (TG-DTA), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, UV-Vis-NIR spectrophotometer are employed to characterize the structure and optical properties. The results illustrated that the photomonomer pentaerythritol triarylate (PETA) directly affects the relative molecular weight of polymer formed by photopolymerization to regulate the morphology and residual carbon of C-TiO2 nanocomposite films, and ultimately affects the solar selective absorption properties. The single layer of as-prepared porous C-TiO2 nanocomposite films exhibits high solar absorptance (α = 0.766-0.863) with low thermal emittance (ε = 0.06-0.12), yielding an optimized photothermal conversion efficiency η = α-ε of (0.706-0.762) corresponding to a wide redundancy PETA concentration 0.3-0.9 (molar ratio to Ti precursor). The proportion of residual carbon contributed by PVP, PETA and poly-PETA, and other substances of the sol is 40.2%, 56.2% and 3.6%, respectively, which might be regulated by a suitable annealing process. Based on these results, porous C-TiO2 nanocomposite films are proved to be a novel candidate material for mid-temperature solar selective absorber coatings.