Multifunctional N and O co-doped 3D carbon aerogel as a monolithic electrode for either enzyme immobilization, oxygen reduction and showing supercapacitance

Highlights: • A novel N and O co-doped 3D carbon aerogels (CAs) with a cross-linked "string-bead" network was prepared by a two-step carbonization technology of preoxidation and carbonization. • The peroxidation process could improve the thermostability and heteroatoms content of polymer-derived carbon materials during the carbonization process. • The developed network structure could increase the electroconductibility and the nanoscale "bead" could provide more effective electrochemical active sites. • Four major reactions were speculated to explain the effect of structural evolution during the preoxidation process on the properties of final products . • This composite CAs displayed excellent electrochemical performance in enzymatic biofuel cells, supercapacitors and ORR. -- Abstract: Herein, a novel N and O co-doped three dimensional (3D) hybrid carbon aerogel (CA) was prepared by a two-step carbonization technology, i.e. preoxidation process (240 °C, air atmosphere) and carbonization process (600∼1000 °C, nitrogen atmosphere). It was found that the peroxidation process could improve the thermostability and heteroatoms content during the carbonization. The obtained CA samples inherited their original morphology of "string-bead" network and had a higher heteroatoms content, while the control samples did not. We focused on the application of this CA in either lactate oxidase-modified, super-capacitive and oxygen reductive electrodes. The fabricated lactate-powered integrated electronic skin could produce a maximum power density of ca. 1.3 mW cm⁻², which allowed powering a multiplexed metabolic electronic in situ. The sample of CF-PVA-PANI₈₀₀ showed the highest specific capacitance of 427.2 F g⁻¹ at a discharge specific current of 0.5 A g⁻¹. The synergistic effect of the N functionalities endowed the sample of CF-PVA-PANI₉₀₀ with similar electrocatalytic activity to a 20 wt% commercial Pt/C catalyst for ORR. This fabrication strategy of carbon aerogel may provide a new alternative for preparing more heteroatom-doped 3D carbon materials in future.