Photocatalytic Properties Of SiC Under Visible Light Irradiation

Energy and environment become the two important topics in the 21st century. Solar energy is enormous and belongs to renewable energy. Photocatalysis is an advanced potential technique to convert solar energy into chemical energy and has many advantages in energy conversion and environment protection. Hydrogen is an important chemical and has the advantage of clean and high combustion value when it is used as the energy carrier. Traditionally, more than 95% hydrogen is produced from the reforming of fossil resource and/or electrolyzing water. Photocatalytic water splitting to produce hydrogen has attracted much attention, and is developing rapidly. In pollution prevention, photocatalytic Cr(VI) reduction using the reductive ability of the photogenerated electrons is also studied widely.In this thesis, a kind of green SiC fine powder, which is used as abrasive material, was characterized by XRD,UV-Vis DRS,TGA and FT-IR, and studied for the splitting of water into hydrogen under visible light irradiation. The results showed that the green SiC fine powder generated H2 in a rate of 24.9μL·g-1?h-1 in pure water; the activity was affected significantly by pH of the solution, the addition of OH- lead to a remarkable increase in the activity; addition of sacrificial reagent, S2-, also lead to a remarkable increase in the activity. The photocatalytic mechanism of SiC was discussed.The activity of SiC with Pt or NiO loading was also studied. The results showed that the promotion effect of Pt loading on water splitting is negligible. This behavior can be explained by the barrier height of the metal-semiconductor junction. NiO loading could accelerate the hydrogen generation, which may be attributed to the charge separation and the adsorption of H+ on SiC surface.The photocatalytic reduction of Cr(VI) on SiC under visible light was also studied. The activity was significantly affected by pH of the solution and the initial concentration of Cr(VI). In addition, the reduction of Cr(VI) on SiC could be related to its adsorption, indicating that the adsorption of Cr(VI) was a crucial step for the photocatalytic reduction of Cr(VI).