Enhancing selectivity of solar absorber using reduced graphene oxide modified nickel oxide nanocomposite thin films

Abstract

Commercial solar selective absorbers prepared through several techniques have encountered drawbacks of necessitating complicated and expensive equipment, substantial materials requirement, and polluting environment. In this context, carbon incorporated metal oxide thin films have shown promise of low-cost, non-toxic, and efficient solar selective absorbers. In particular, association of reduced graphene oxide (rGO) and nickel oxide (NiO) could facilitate highly ascertained optical properties, environment friendliness, and low-cost. Present study focuses on preparing a novel, high performance, and low-cost rGO-NiO solar selective absorber thin films. Thin films comprised of reduced graphene oxide modified nickel oxide nanocomposites (rGO-NiO NCs) were prepared through solvothermal route and coated on aluminum (Al) substrates by dip-coating technique. The rGO-NiO NCs examined using X-ray diffractometer revealed formation of face centered cubic crystallite structure. The scanning electron microscope images disclosed spherical morphology of NiO decorated on the rGO sheets. The spectra derived from energy-dispersive X-ray spectroscopy ascertained absence of peaks corresponding to impurities. The Raman investigation exhibited high intensity ratio (0.97) of the rGO-NiO NCs that described higher disorder and binding sites. The optical property analysis of the rGO-NiO NC (0.2 wt% rGO) thin film performed in UV–vis-NIR reflectance spectroscopy showed high absorptance (α = 88.03 %) and low thermal emittance (ε = 4.5 %), which eventually delivered high solar selectivity (ξ) of 19.56. These findings suggest that the prepared 0.2 % rGO-NiO NC thin film can be utilized as an appropriate selective absorber for solar to thermal energy conversion.