Optimal design and preparation of titania-supported CoPc using sol-gel for the photo-reduction of CO₂

CoPc-loading titania (CoPc/TiO₂) was synthesized by an improved sol-gel method using a homogeneous hydrolysis technique. In order to increase C1 products in the photo-reduction of CO₂, preparation conditions of photo-catalysts were optimized using a four-level OAD16 (4⁵) matrix in which molar ratio of reacting species, solvent, pH, mass ratio of CoPc to TiO₂, and calcining temperature were chosen as main parameters. The results obtained by orthogonal array design (OAD) method indicate that calcining temperature was the most important parameter influencing the photo-reduction of CO₂. Under optimal experimental conditions the total yield of reduction products of CO₂ in NaOH aqueous solutions was 406.65 μmol/g-catal. The grain size of CoPc/TiO₂ was uniform with an average diameter of approximately 11 nm. In addition, the catalyst was characterized by X-ray powder diffraction, scanning electron microscopy, UV-vis DRS, BET and FT-IR spectroscopy. CoPc/TiO₂ catalyst synthesized by sol-gel exhibited relatively high photochemical activity for the reduction of CO₂ compared with TiO₂ prepared by sol-gel method.