▎ 摘　　要

NOVELTY - Preparing porous sheet nickel cobaltite (NiCo2O4)/nitrogen and sulfur co-doped reduced graphene oxide composite electrode material comprises e.g. dispersing the prepared graphene oxide in 20-40 ml de-ionized water for 1-3 mg/l, adding 30-80 mmol/l thiourea to dissolve, stirring, mixing with nickel(II) nitrate, cobalt nitrate and urea, performing hydrothermal reaction at 100-200 degrees C for 4-14 hours, calcining at 300-600 degrees C for 1-4 hours, fully grinding, adding 50-200 mu l 5-20% naphthol solution, 400-800 mu l absolute ethanol, placing it in a centrifuge tube and mix, ultrasonic processing for 15 -30 minutes to obtain uniform ink-shaped solution, pipetting out the suspension of 5-20 mu l by using a sampling needle, slowly dropping into glassy carbon electrode, and drying at room temperature to obtain final product. USE - The composite electrode material is for electrochemical detecting mercury(II), copper(II), and cadmium(II) heavy metal ions. ADVANTAGE - The method: is easy to carry out, has mild reaction condition and low cost; improves the conductive performance of the material; increases the contact area of the material with the electrolyte solution; and ensures the material having very high specific capacitance and excellent electrochemical stability. DETAILED DESCRIPTION - Preparing porous sheet nickel cobaltite (NiCo2O4)/nitrogen and sulfur co-doped reduced graphene oxide composite electrode material comprises (i) taking graphite powder, potassium persulfate and phosphorus pentoxide in a mass ratio of 1-3:1:1, 10-20 ml 98% concentrated sulfuric acid, turning on the oil bath heating device, first adding 98% concentrated sulfuric acid into a beaker, turning on the stirring device, adding graphite powder into concentrated sulfuric acid in 3 times, stirring for 10-30 minutes, slowly adding potassium persulfate, stirring evenly, adding phosphorus pentoxide slowly, and reacting at 60-100 degrees C in oil bath for 4-8 hours, reacting, allowing to stand at room temperature for overnight, slowly diluting with water to make all the reactants in the beaker become a solution, and performing centrifugal washing until the pH of the centrifugal solution is 7, and vacuum drying the centrifugal product for overnight to obtain off-white pre-oxidized grapheme, (ii) taking 15-30 ml concentrated sulfuric acid under the condition of ice bath, turning on the stirring device, maintaining the temperature at 0 degrees C for 10-30 minutes, stirring the obtained pre-oxidized graphite for 10 minutes, adding 3-3 g potassium permanganate, adding 3 times, maintaining the whole reaction system at 15 degrees C in the process, reacting at 15 degrees C for 2-4 hours, gradually adding 50-100 ml de-ionized water, heating at 20 degrees C, reacting for 2-4 hours, gradually adding 100-400 ml de-ionized water and 3-8 ml 30% hydrogen peroxide, reacting for 0.5-2 hours, allowing to stand for overnight, adding 150-300 ml de-ionized water, gradually adding 30-60 ml concentrated hydrochloric acid, and centrifuging the whole reaction system, water washing to neutral, freezing and drying to obtain bright yellow graphene oxide, (iii), dispersing the obtained graphene oxide in 20-40 ml de-ionized water for 1-3 mg/l, adding 30-80 mmol/l thiourea to dissolve, stirring for 10-30 minutes, transferring into a reaction kettle, performing hydrothermal reaction at 150-200 degrees C for 4-10 hours to obtain nitrogen-sulfur co-doping reducing graphene oxide, (iv) mixing nickel(II) nitrate, cobalt nitrate and urea in a mol ratio of 1:2:3-9, dissolving in de-ionized water to form 0.5-3 mol/l mixed solution, dispersing the nitrogen-sulfur co-doped reducing graphene oxide in the mixed solution, stirring for 1 hours, placing it into a hydrothermal kettle, performing hydrothermal reaction at 100-200 degrees C for 4-14 hours to obtain cobalt(II) hydroxide-nickel(II) hydroxide/nitrogen and sulfur co-doped reduced graphene oxide, the molar ratio between mixed salt, nitrogen and sulfur co-doped reduced graphene oxide is 0.5-3:1, (v) placing cobalt(II) hydroxide-nickel(II) hydroxide/nitrogen and sulfur co-doped reduced graphene oxide in a muffle furnace under the air atmosphere temperature, calcining at 300-600 degrees C for 1-4 hours to obtain nickel cobaltite/nitrogen sulfur co-doped reduced graphene oxide composite material, and (vi) placing nickel cobaltite/nitrogen sulfur co-doped reduced graphene oxide composite material in agate mortar for fully grinding, taking 1-5 mg the ground composite material, adding 50-200 mu l 5-20% naphthol solution, 400-800 mu l absolute ethanol, placing it in a centrifuge tube and mix, ultrasonic processing for 15 -30 minutes to obtain uniform ink-shaped solution, pipetting out the suspension of 5-20 mu l by using a sampling needle, slowly dropping into glassy carbon electrode, and drying at room temperature to obtain final product. An INDEPENDENT CLAIM is also included for porous sheet nickel cobaltite (NiCo2O4)/nitrogen and sulfur co-doped reduced graphene oxide composite electrode material prepared by above method. The composite electrode material is used for electrochemical detecting mercury(II), copper(II), and cadmium(II) heavy metal ions. The composite electrode material has detection range of 0.1-100 mu mol/l, cadmium(II) sensitivity of 4-8 mu A/ mu M, copper(II) sensitivity of 6-18 mu A/ mu M and mercury(II) sensitivity of 2-5 mu A/ mu M.