Two-dimensional correlation infrared spectroscopy reveals the evolution of functional groups governing biochar oxidation resistance

/C=C → C-OH/C=O (for DMB500), C=O → =C-H/aromatic C-H (for WSB700), and C=O → aromatic C-H/carbonate → =C-H (for DMB700). MW2D-COS analysis confirmed aromatic C=C/CH₂/C=C degradation and C=O formation in WSB500 and DMB500 during oxidation, aligning with significant alterations in C, O, fixed carbon, DOC, and atomic ratios (p < 0.01). WSB700 demonstrated superior oxidation resistance. These findings provide a mechanistic basis for predicting biochar's long-term carbon sequestration potential and guide the selection of optimal pyrolysis conditions for specific environmental applications.