Abstract

Heteroatom doping represents a feasible strategy to enhance electrochemical performance of carbon-based electrodes. However, current synthesis routes rely on non-scalable methods, and resulting doped electrodes frequently exhibit poor long-term stability, limiting practical implementation. This study addresses both chal-lenges through a mechanochemical approach for nitrogen and boron co-doping of nanoporous carbons using ammonium borate salts. The synthesis achieves unusually high surface boron content (ca. 8 at. %), with a surface chemistry dominated by oxygen-coordinated boron species, alongside stable nitrogen incorporation (ca. 2 at.%). Despite moderate specific surface areas (ca. 960 m2 g-1), the best-performing material delivers specific energies of 5.9 W h kg-1 at 120 W kg-1 in 1 M H2SO4 and 8.4 W h kg-1 at 359 W kg-1 in 1 M Na2SO4. Floating-time protocols reveal counterintuitive electrochemical evolution in acidic media, wherein voltage holds progres-sively reduce charge-transfer resistance, contrasting with conventional degradation in neutral electrolyte at elevated voltages. Long-term cycling confirms exceptional 94% energy retention after 30,000 cycles at 5 A g-1. These findings establish mechanochemical N,B co-doping as a viable route for doped carbon electrodes, while revealing electrolyte-dependent aging mechanisms with exceptional resilience in acidic media.