Tailoring graphitic nitrogen-enriched electrocatalytic membranes for acetaminophen degradation: Mechanistic insights into the site-specific reactive process

The pressing concern of pharmaceuticals and personal care products (PPCPs) in water, particularly with the increased usage of acetaminophen (ACE) during the COVID-19 pandemic, draws attention to the necessity for efficient water treatment. This study introduces tailored electrocatalytic carbon membranes featuring naturally doped nitrogen functionalities for energy-efficient electrochemical water treatment. The introduction of graphitic-N functionality into polyacrylonitrile electrospun fibers can be achieved through carbonization and activation processes, forming a freestanding electrocatalytic carbon membrane (ECM). In addition, in-situ immobilization of TiO₂ on the ECM enables a deeper exploration of catalyst's role in generating reactive oxygen species. As demonstrated, the enriched graphitic N in the membrane contributed to an enhanced electron transfer ability, resulting in extraordinary electrocatalytic activities. Note that graphitic N also served as site-specific active sites for ACE degradation. By utilizing the electrocatalytic carbon membranes, complete degradation of ACE was achieved within 60 min, with an electrical energy per order (EEO) of approximately 0.6 kWh/m³/order. This demonstrates the high degradation efficiency and low energy requirement of the system. Moreover, scavenger experiments demonstrate the significant involvement of O₂^•–, •OH and ¹O₂ in ACE degradation. Within the TiO₂ decoration, there is a notable enhancement in the contribution of •OH during the degradation process. Overall, this study not only innovates electrocatalytic membrane design and catalyst immobilization but also advances our understanding of site-specific reactive processes in electrified water treatment.