Spectrally selective coating of nanoparticles (Co3O4:Cr2O3) incorporated in carbon to captivate solar energy

Innovatory nanocomposite comprising nanomaterials Co3O4:Cr2O3 and carbon (fuel ash) was designed to absorb solar energy. Different concentration ratios of Co3O4 and Cr2O3 nanoparticles were utilized as a dopant for fuel thin films synthesis via spin and casting methods on glass and aluminum substrates. The optical properties of the modified films demonstrated in the range of 250 to 1300 nm. The data were interpreted in terms of a phonon-assisted theory. Energy gap (E-g) of doped C was calculated with different concentration ratios of Co3O4:Cr2O3 (0.5:2.5, 1:2, 1.5:1.5, 2:1, 2.5:0.5) wt%, and fixed concentration of C in 7wt%. The results showed E-g of the doped samples in the range of 2.9 to 3.9 eV. In addition, the intensity of the solar radiation was measured. The absorptivity was in the range of 88 to 93.6%. The above results are comparable to those of semiconductors and have high absorptivity values when the nanocomposite was utilized on a flat plate collector as a coating to trap and absorb solar energy.