Preparation of passion fruit peel biochar and its application in simultaneous sensing detection of hydroquinone and catechol

Passion fruit peel was treated with or without phosphoric acid activation followed by direct pyrolysis and staged pyrolysis respectively, to obtain four types of passion fruit peel biochar (PFPB) materials including direct pyrolysis-PFPB (D-PFPB), staged pyrolysis-PFPB (S-PFPB), direct pyrolysis-phosphoric acid activated PFPB (PD-PFPB), and staged pyrolysis-phosphoric acid activated PFPB (PS-PFPB). This study is to screen out the PFPB with the best electrochemical property as the electrode modification material. A series of structural and electrochemical characterizations revealed that PS-PFPB featured the largest defect degree, specific surface area and pore capacity and the best electrochemical property, was then applied to modify the glassy carbon electrode (GCE) after mixed with chitosan (CS), to fabricate the electrochemical sensing electrode PS-PFPB/CS/GCE for the simultaneous detection of hydroquinone (HQ) and catechol (CC). The operating condition was investigated and performance of the fabricated sensing electrode was evaluated. The experimental results indicated that the fabricated sensing electrode had an optimal response signal for simultaneous detection of HQ and CC at pH = 7.4 in phosphate buffer solution, with two linear detection ranges (LDRs) of low concentration (2.0–40.0 µM) and high concentration (40.0-200.0 µM), and limit of detections (LODs) of 0.28, 0.19 µM and 1.39, 1.05 µM for HQ and CC detections in the low and high concentration ranges, respectively. The fabricated sensing electrode also exhibited a good reproducibility, reproducibility and stability as well as good anti-interference ability, and was applied for the simultaneous detection of HQ and CC in real seawater sample successfully by using the standard addition method. This study provides useful reference information for the preparation of novel biochar materials, and their application in electrochemical sensing detections.