Isolated Cobalt Atoms on N-Doped Carbon as Nanozymes for Hydrogen Peroxide and Dopamine Detection

Single-atom catalysts are becoming a hot research topic owing to their unique characteristics of maximum specific activity and atomic utilization. Herein, atomically dispersed Co on a N-doped carbon matrix with an enzyme-like M–Nx structure has been developed as a bifunctional biosensor to detect hydrogen peroxide (H2O2) and dopamine (DA). It features 100% atomic utilization, high electrochemical activity and selectivity, and strong stability in various pH environments. The abundance of Co-Nx sites can be increased via regulating calcination temperature, and as a result, the sensing performance is significantly improved. This platform could selectively catalyze the oxidation of DA and the reduction of H2O2 at different holding potentials. The optimal Co-N-C-800 affords high sensitivity (H2O2: 943.9 μA mM–1 cm–2 and DA: 979.6 μA mM–1 cm–2), low detection limit (H2O2: 0.13 μM and DA: 0.04 μM), high selectivity, and robust stability. At the same time, H2O2 and DA released by PC12 can be detected, which proved the feasibility of the enzyme-like single-atomic materials in electrochemical biosensing.