▎ 摘　　要

NOVELTY - Preparing bifunctional transition metal nitride heterojunction electro-catalyst involves preparing graphite-carbon nitride for use, weighing a certain amount of transition metal salt mixture and urea, dissolving them in water, and ultrasonically treating them for 30-60 minutes. Graphene oxide and graphite-carbon nitride are weighed and dissolved in an aqueous solution, and ultrasonically treated. The obtained transition metal salt solution is slowly poured into the obtained graphene oxide and graphite-carbon nitride solution and the mixture is stirred to form a hydrogel. The resulting hydrogel is transferred into steel autoclave lined with Teflon (RTM: Polytetrafluoroethylene). The reaction is heated in an oven, and after the reaction is completely cooled, the precipitate is collected by centrifugation. The sample is collected, ground and transferred to a crucible. The calcined black sample is taken out from the quartz tube. USE - Method for preparing bifunctional transition metal nitride heterojunction electro-catalyst for use in electrocatalytic cathode oxygen reduction/oxygen evolution reaction. ADVANTAGE - The method enables providing transition metal nitride heterojunction with excellent double function as oxygen reduction/oxygen precipitation reaction electro-catalyst, low cost, simple synthesis, and excellent oxygen reducing/oxidizing separating performance. The method is simple, cost-effective, and can realize mass production. DETAILED DESCRIPTION - Preparing bifunctional transition metal nitride heterojunction electro-catalyst involves preparing graphite-carbon nitride for use, weighing a certain amount of transition metal salt mixture and urea, dissolving them in deionized water, and ultrasonically treating them for 30-60 minutes. Certain amount of graphene oxide and graphite-carbon nitride are weighed and dissolved in an aqueous solution, and ultrasonically treated for 2-4 hours. The obtained transition metal salt solution is slowly poured into the obtained graphene oxide and graphite-carbon nitride solution and the mixture is stirred to form a hydrogel. The resulting hydrogel is transferred into a steel autoclave lined with Teflon(RTM: Polytetrafluoroethylene). The reaction is heated in an oven, and after the reaction is completely cooled, the precipitate is collected by centrifugation, washed several times with deionized water and ethanol, respectively, and then centrifuged and dried in a vacuum oven. The sample is collected, ground and transferred to a crucible, which is then placed in a tube furnace, and program the temperature to 700-900 ℃ for 2-4 hours annealing in a certain proportion of ammonia gas and argon gas mixture. After naturally cooling to room temperature, the calcined black sample is taken out from the quartz tube to obtain the transition metal nitride heterojunction electro-catalyst. An INDEPENDENT CLAIM is also included for a method of electrocatalytic cathode oxygen reduction/oxygen evolution reaction, which involves: (1) dispersing the transition metal nitride heterojunction electro-catalyst in a mixed solution of water, ethanol and naphthol, and ultrasonically dispersing to obtain a uniformly dispersed electrode solution; (2) taking 5-20 µL of electrode solution and evenly apply it to the surface of the clean disk electrode, and let it dry naturally at room temperature to obtain the disk electrode modified by the transition metal nitride heterojunction electro-catalyst; (3) configuring 0.1moL.L-1potassium hydroxide solution as electrolyte and transferring to quartz electrolytic cell; (4) using the disk electrode modified by the transition metal nitride heterojunction electro-catalyst as the working electrode; (5) using the graphite rod electrode as the counter electrode, saturated silver/silver chloride electrode as the reference electrode; (6) using three-electrode test system to test its oxygen reduction/oxygen evolution performance.