Cobalt single atom sites in carbon aerogels for ultrasensitive enzyme-free electrochemical detection of glucose

• Carbon aerogels with atomically dispersed cobalt by pyrolysis of hydrogel precursor. • CoN x moieties at nanopore edges show preferred adsorption of glucose. • Electrocatalytic activity of CoN x towards glucose oxidation. • Excellent detection of glucose in artificial saliva and human serum samples. Enzyme-free electrochemical glucose sensors have been attracting extensive attention, due to high sensitivity, excellent stability, and low cost, as compared to the conventional counterparts based on biological enzymes such as glucose oxidase. Within this context, development of low-cost, high-performance electrode catalysts represents a critical first step, and nanocomposites with atomically dispersed metal sites have emerged as viable candidates. In this study, nitrogen-doped carbon aerogel (NCA) embedded with CoN x sites is derived pyrolytically from biomass hydrogels and serves as an electrode catalyst for the detection of glucose. The three-dimensional porous skeletons of NCA help disperse the Co single atom sites and facilitate the mass transfer during electrochemical reaction. Theoretical calculations reveal that the single metal sites (CoN 3 and CoN 4 ) at the edge of nanopores show optimal adsorption towards glucose, and likely make a dominant contribution to the high activity in glucose detection. In electrochemical measurements, the NCA-Co based, enzyme-free glucose sensor shows a detection limit of 0.1 μM, with a wide linear range from 0.5 μM to 6 mM, good stability, high selectivity and excellent reproducibility. Notably, this sensing platform also exhibits an excellent performance in determining the glucose contents in artificial saliva and human serum samples, indicating great potential for practical applications.