TECHNOLOGY FOCUS - METALLURGY - Preferred Method: The nitric acid and sulfuric acid modified multi-wall carbon nanotube is prepared by configuring concentration of mixed nitric acid and sulfuric acid with volume ratio of 1:2.5-3.5; mixing with carbon nanotube to obtain solid-liquid solution with solid to liquid ratio of 5-10 g/L, mixing with acid solution while stirring at 70-90 degrees C for 8-10 hours; filtering and repeatedly washing with water to neutralize the filtrate; and dissolving with water at solid to liquid ratio of 2 g/L. The pre-treatment of titanium dioxide powder is carried out by grinding 50-100 nm titanium dioxide powder until it becomes homogeneous; putting into the muffle furnace and calcining at 400-500 degrees C for 3-5 hours; adding 0.3-0.5 mol/L nitric acid solution, baking at 150-250 degrees C for 2 hours and at 450-550 degrees c for 2-3 hours; taking out, adding 0.3-0.5 mol/L hydrofluoric acid, and stirring overnight for 10-12 hours; and filtering, subjecting to ultrasonic, repeatedly washing with water to neutralize filtrate, drying at 70 degrees C, and grinding for further use. The TiO2-CNT composite carrier material is prepared by mixing pretreated titanium dioxide with deionized water to obtain a liquid ratio of 2 g/L, stirring for 20-40 minutes, adding with modified multi-wall carbon nanotube, and continuously stirring for 2 hours; adding with isopropanol while continuously stirring for 0.5-1.5 hours; adding with ethylene glycol and overnight stirring for 8-12 hours; filtering and washing with 5-10 times to obtain TiO2-CNT composite carrier material; and dissolving in an aqueous solution to obtain a composite ratio of solid carrier material mixed solution of 10-20 g/L. The mass ratio of titanium dioxide and modified multi-wall carbon nanotube is 1-1:2. The volume ratio of isopropanol and ethylene glycol is 1:2.5-1:3.5. The palladium nanoparticle catalyst is prepared by dispersing palladium chloride in deionized water and subjecting to ultrasonic at 40-50 degrees C for 20-30 minutes to obtain 0.1-1 mg/ml aqueous solution of palladium chloride; adding to TiO2-CNT composite carrier material while stirring for 1-2 hours; adding with sodium borohydride while continuously stirring for 8-10 hours; and washing with water and drying at 60-80 degrees C. The mass ratio of sodium borohydride and palladium chloride is 50:1-70:1.