China Nonferrous Metallurgy

Photothermal conversion is an effective solar energy utilization technology, and its efficiency depends on the light absorption capacity of photothermal conversion materials. In this paper, Black TiO₂ steel slag/graphite porous materials were prepared in situ by high temperature calcination with titanium dioxide as raw material, steel slag as skeleton, graphite as reducing agent, starch as pore-forming agent and polyvinyl alcohol solution as binder. The phase, microstructure, surface element composition and valence state and light absorption ability of the porous materials were characterized by XRD, SEM, XPS and UV-Vis, and the porosity and photothermal properties were tested. The results of characterization and porosity show that the main phases of the porous materials are composed of anatase TiO₂ CaTiO₃, C and Ca₃Mg(SiO₄)₂, the boundaries between the phases are clear. During the calcination process, part of Ti⁴⁺ on the crystal surface of TiO₂ was reduced to Ti³⁺ and oxygen vacancies were formed, which confirmed that TiO₂ was transformed into Black TiO₂.The porosity of the porous material with a starch ratio of 21.74% is 30.5% and has the smallest band gap. The results of photothermal performance test showed that with the increase of starch ratio, the water evaporation rate and evaporation efficiency of porous materials increased significantly at first and then decreased slightly; When the mass ratio of TiO₂, graphite powder, polyvinyl alcohol solution and steel slag is fixed at 1∶1∶1∶4, and the starch ratio is 18.52%, the water evaporation rate and photothermal conversion efficiency of the porous material can reach 1.47kg·m^-2·h^-1 and 69.18%.