Mechanistic insights into oxygen–boron co-doping in activated carbon: Tailoring surface chemistry and wettability

Abstract

Oxygen (O) and Boron (B) heteroatom doping has emerged as a promising strategy to enhance the capacitive performance of activated carbon (AC) for supercapacitors. However, the synergistic mechanism between these heteroatoms remains ambiguous due to intertwined morphological and compositional changes during conventional doping processes. This study employs a stepwise doping methodology to independently control O and B concentrations while preserving the structural integrity of AC. Through sequential high-temperature B doping and low-temperature oxidation, dual-doped AC (AC-O-B) retains comparable specific surface area and pore structure to pristine AC. Electrochemical evaluations reveal that O–B double doping has no significant effect on the double-layer capacitance, but it greatly improves the pseudocapacitance. Mechanistic analysis demonstrates that O doping introduces abundant C–O groups and facilitating the formation of BC₂O structures via B integration. The presence of C–O groups and BC₂O structure not only enhance surface wettability but also optimize charge transfer kinetics and redox-active site density. This work provides critical insights into heteroatom co-doping strategies for designing high-performance carbon-based supercapacitors.