▎ 摘　　要

NOVELTY - Graphene composite material comprises 9-15 pts. wt. magnesium oxide, 8-15 pts. wt. chromium oxide, 7-12 pts. wt. zirconia, and 60-75 pts. wt. graphene. The composite materials are formed by graphene supported metal oxides, where metal oxide is a mixture of magnesium oxide, chromium oxide and zirconium oxide. USE - The graphene composite material is useful in gas sensors for monitoring formaldehyde (claimed). ADVANTAGE - The graphene composite material: quickly and accurately determine trace formaldehyde in the air on site without interference from other co-existents. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing graphene composite material comprising (i) adding graphite into fuming sulfuric acid slowly under continuous stirring, heating at 40-50 degrees C and continue to stirring for 2-3 hours, adding oxalic acid equal to graphite, stirring for 1-2 hours, then suction filtering, and washing the filtrate until neutral, (ii) adding filtrate into the potassium permanganate concentrated sulfuric acid solution, heating at 55-60 degrees C and continue to stirring for 2-3 hours, then adding hydrogen peroxide aqueous solution, stirring for 1-2 hours, then suction filtering and washing the filtrate with water to neutrality to obtain graphene oxide, (iii) dissolving magnesium salt and zirconium salt in hydrochloric acid aqueous solution to form solution A, dissolving chromium salt in citric acid aqueous solution to form solution B under continuous stirring, adding solution A into solution B, stirring for 1-2 hours, heating at 90-95 degrees C and then adding agar powder and stirring until it is completely dissolved, cooling to room temperature to form a gel, drying the gel in a box-type resistance furnace, heating at 200-250 degrees C at a rate of not greater than 3 degrees C per minute, and maintaining temperature for 4 hours, heating at 400-450 degrees C at a rate not exceeding 3 degrees C per minute, and maintaining this temperature for 3 hours, naturally cooling to room temperature to obtain composite metal oxide composed of magnesium oxide, zirconium dioxide and chromium trioxide, and (iv) adding this composite metal oxide into 15-20% hydrazine hydrate aqueous solution under continuous stirring, then adding graphene oxide, heating at 45-50 degrees C, stirring at constant temperature for 4-5 hours, naturally cooling, filtering, washing with deionized water, and then drying in a vacuum oven to obtain graphene-supported composite powder material composed of magnesium oxide, zirconium dioxide and chromium trioxide.