Pyrolysis temperature determines aging effects on the electron transfer and exchange properties of pyrogenic carbon

Abstract Pyrogenic carbon (PyC) possesses electron transfer and exchange capabilities that can facilitate redox reactions in various geochemical and biochemical processes. The long-term environmental persistence of PyC makes it susceptible to substantial alterations in its physical and chemical properties through aging. However, there is a lack of research on how aging impacts PyC’s electron transfer and exchange properties. This study investigated the effects of aging on PyC samples derived from four feedstocks and prepared at two different pyrolysis temperatures. Three aging methods, including chemical aging, freeze–thaw cycling, and natural aging over a year, were employed. The results indicate that aging significantly enhanced the conductivity of certain PyC samples produced at 350 °C by more than three orders of magnitude, potentially attributed to the enrichment of redox-active functional groups. Conversely, for PyC produced at 750 °C, aging damaged the polyaromatic carbon matrices, resulting in reduced conductivity. Aging was found to decrease the electron-donating capacity (EDC) while increasing the electron-accepting capacity (EAC) of PyC produced at 350 °C, primarily due to a reduction in electron-donating C–OH groups and an increase in electron-accepting O–C=O groups. These findings shed light on the aging effects on the electron transfer and exchange properties of PyC and offer valuable insights for assessing PyC’s role in biogeochemical processes. Graphical Abstract