▎ 摘　　要

NOVELTY - Single-atom catalyst comprises graphitic carbon nitride as a carrier, and a single copper atom loaded on the carrier as an active component, where the atomic percentage content of the active component in the single-atom catalyst is 0.07-0.2%, and graphitic carbon nitride comprises mesoporous graphitic (mpg)-carbon nitride. USE - The catalyst is useful in preparing the microelectrode for measuring the concentration of hydrogen peroxide in the brain (all claimed). ADVANTAGE - The catalyst: has large specific surface area, low content of active components, high selectivity to hydrogen peroxide and good stability. The microelectrode: adopts a single-atom catalyst with high selectivity as an electrocatalyst; and realizes the accurate detection of hydrogen peroxide on the electrode without interference from oxygen and most other substances in the brain. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: preparing the single-atom catalyst, comprising preparing graphite phase carbon nitride dispersion, where the graphite phase carbon nitride comprises mpg-carbon nitride, adding the copper salt solution to the graphite phase carbon nitride dispersion, stirring, separating and drying to obtain a catalyst precursor, calcining the catalyst precursor in a mixed atmosphere of hydrogen and an inert gas or calcining in a hydrogen atmosphere, and cooling; a microelectrode, comprising an electrode, a complex layer coated on the surface of the electrode, and a polymer layer for covering the complex layer, where complex layer comprises a single-atom catalyst or a single-atom catalyst and a carbon material, and the single-atom catalyst prepared by above mentioned method; and preparing the microelectrode, comprising dispersing the single-atom catalyst and optional carbon material in a solvent to obtain a dispersion, coating electrode tips with the dispersion, drying, immersing the dried electrode tip in the polymer solution, taking out and drying.