Azobisisobutyronitrile-induced biocarbon with high edge-nitrogen density: A metal-free redox-catalyst for electrochemical detection and reduction of 4-nitrophenol

Abstract

Enhancing the specific nitrogen dopant concentration within the sp²-C domain of carbon materials is a promising approach to developing metal-free redox catalysts for electrochemical detection and remediation, thereby eliminating the need for toxic chemicals and complex procedures. However, achieving precise control over the type and concentration of nitrogen within the sp²-C domain during pyrolysis remains challenging. In this study, we synthesized unique nitrogen-doped biocarbons (AIBN_XOC) by pyrolyzing orange peel waste with azobisisobutyronitrile (AIBN) under nitrogen atmosphere, introducing AIBN as a novel nitrogen dopant. These material were tested for electrochemical detection and reduction of 4-nitrophenol (4-NP). By varying the concentrations of AIBN (X), a nitrogen-rich carbon framework with distinctive functionalities, such as pyridinic-N, graphitic-N, and carbonyl (C=O) groups was achieved. These functionalities successfully enhanced electrochemical performance by facilitating accelerated electron transfer and increasing 4-NP adsorption. The optimized AIBN₁OC-modified glassy carbon electrode (AIBN₁OC/GCE) exhibited excellent sensing capabilities, with a low detection limit of 0.4 nM and strong selectivity against potential interferences. Additionally, AIBN_XOC were applied for the catalytic reduction of 4-NP to 4-aminophenol in the presence of NaBH₄, leveraging the synergistic effects of pyridinic-N and CO sites for efficient hydride (H^δ+/H^δ-) formation. Practical applicability was demonstrated by detecting 4-NP in river water samples, showcasing the material's potential for real-world environmental monitoring.