▎ 摘　　要

NOVELTY - A composite electrocatalyst is formed by loading stannic oxide which is modified by graphene, on sepiolite. The mass ratio of the sepiolite to modified stannic oxide is 0.5-1.5:1. The mass ratio of the graphene to stannic oxide is 0.1-2.5:1000. USE - Composite electrocatalyst. ADVANTAGE - The composite electrocatalyst has high catalytic efficiency, stable quality and can be used repeatedly, and is economically formed by simple process. DETAILED DESCRIPTION - Preparation of composite electrocatalyst, which involves grinding the sepiolite, cracking in a mortar, filtering with 100-meshes sieve, soaking, cleaning with distilled water for three times, drying at 90-120 degrees C, grinding in a mortar, filtering with 100-meshes sieve to obtain sepiolite powder, where mass ratio of sepiolite to distilled water is 1:5-10, obtaining colorless and transparent graphene-stannic chloride sol by adding graphene (0.5-15 mg) in 20-100 mL of stannic chloride having concentration of 5-40 mass%, oscillating uniformly, carrying out ultrasonic dispersion for 20-30 minutes using constant-temperature magnetic force heating stirrer to stir uniformly, dripping aqueous ammonia having concentration of 0.3-5 mol/L with a speed of 20-30 drops/minute at the same time when stirring, mixing the obtained sepiolite powder with graphene-stannic chloride sol in the mass ratio of 1:3-60, using the constant temperature magnetic force heating stirrer to stir uniformly, aging for 10-18 hours, centrifuging using a centrifugal machine, drying the centrifuged solid at 80-90 degrees C, placing in a muffle furnace, roasting at 400-600 degrees C for 2-4 hours, grinding using mortar after cooling to room temperature and filtering with 100-meshes sieve.