▎ 摘　　要

Despite the emergence of nitrogen-doped graphene as a noble-metal free electrocatalyst for oxygen reduction reaction, its participation in the electrochemical conversion mechanism is not well -established. In the present study, functionalities of the nitrogen species on the oxygen reduction activ-ity of bilayer graphene were investigated by combining atom-specific X-ray spectroscopy, Raman spec-troscopy, and density functional theory calculations with electrochemical activity tests in alkaline media. Among various nitrogen species, pyridinic nitrogen as the dominant species improved the electro-chemical activity of bilayer graphene, which was followed by graphene bilayers doped with graphitic nitrogen in majority. Polarization curves revealed a significantly high electrocatalytic oxygen reduction activity of the nitrogen-doped bilayer graphene where the pyridinic nitrogen was the major dopant. This improved activity was confirmed by the lowest overpotential and Tafel slope (78.9 mV/dec). The enhanced interaction of graphene bilayers doped with pyridinic nitrogen is shown to be the main reason for this improvement.(c) 2023 Elsevier Ltd. All rights reserved.