▎ 摘　　要

NOVELTY - Preparing nitrogen-doped molybdenum selenide involves dissolving selenium powder in the reducing agent hydrazine hydrate to obtain a first solution, dissolving sodium molybdate, biomass template diatomaceous earth, and graphene oxide (GO) powder in water to obtain a second solution. The first solution and the second solution are mixed uniformly, put them into a hydrothermal kettle and conduct a hydrothermal reaction at 180-220 degrees C for 8-12 hours to obtain a third solution. The third solution is centrifuged and dried to obtain a molybdenum selenide / graphene mixed powder, and placed the molybdenum selenide / graphene mixed powder in an ammonia atmosphere for an annealing reaction. The calcined powder is etched with hydrofluoric acid to obtain nitrogen-doped selenide with a three-dimensional network structure and replicated the template morphology. USE - Method for preparing nitrogen-doped molybdenum selenide used for potassium ion energy storage device, where the potassium ion energy storage device includes a potassium ion half cell and a potassium ion hybrid capacitor. (all claimed). ADVANTAGE - The method enables to prepare nitrogen-doped molybdenum selenide, that can well alleviate the volume expansion caused by potassium ion insertion and extraction, and the doping of N can increase various active sites on the surface of the active material to enhance the potassium storage performance, and compounding with graphene can improve the conductivity, cycle stability and mechanical stability of active materials.