Preparation and characterization of porous carbon–titania nanocomposite films as solar selective absorbers

Abstract

Newly proposed selective solar absorbers of porous carbon–titania nanocomposite films with a well-defined interconnected macropores structure were prepared via a polymer-assisted photopolymerization-induced phase-separation method. The microstructure and optical properties of as-deposited nanocomposite films were characterized and discussed in detail. The results show that non-ionic water-soluble polymer polyvinylpyrrolidone works as a sol modifier advantaging the mean size of the interconnected macropores, residual carbon content, and films thickness, but suppresses the order degree of the carbon remained in the films. The high-resolution transmission electron microscopy demonstrated that a small amount of graphite particles with size of around 1.1nm embedded in the cavity of the porous while the wall of the porous consists of amorphous carbon and titania composites. The single layer of as-prepared porous C/TiO2 nanocomposite films exhibits high solar absorptance (α=0.928–0.959) with low thermal emittance (ε=0.074–0.105), yielding an optimized photothermal conversion efficiency η=α−ε of 0.864 corresponding to a film thickness of around 338nm, indication of such film is fair enough to serve as an excellent solar absorber.