Preparation of defect-rich, N-doped activated carbons via high-energy ball milling and investigation of their electrochemical performances towards hydrogen peroxide sensing

N-doped, defect-rich activated carbons (ACs) were prepared using high-energy ball milling (BM) followed by a heat treatment to prepare metal-free, highly active carbon-based electrocatalysts. To investigate the effect of milling process on the physicochemical and electrochemical properties, a series of milling durations ranging from 2.5 to 15 min were applied. It was seen that while 2.5-min milling process was insufficient to destroy the AC structure and achieve high defect concentration, 5-min milling process yielded a significant change in the X-ray diffraction reflection. X-ray photoelectron spectroscopy results suggested that contents of N-binding sites were altered depending on the milling time. Electrochemical performance results indicated that both N doping and ball milling processes had significant effects on the H₂O₂ reduction capabilities. N-AC-5BM-based sensors showed a high sensitivity of 301.24 μA mM⁻¹ cm⁻², which is 2.5 and 1.7 times greater than pristine AC (119.3 μA mM⁻¹ cm⁻²) and N-doped AC (180.6 μA mM⁻¹ cm⁻²), respectively. In addition, 5-min ball-milling process widened the linear range profoundly, and a wide linear range of 0.1–52 mM was obtained. The performance of the sensors was compared with both metal-free and noble-metal containing sensors and the findings displayed that N-AC-5BM-based sensors had higher performances than even noble metal-containing sensors.