Degradable AgNWs/MWNT nanocomposite electrodes supported on pomelo peel for formaldehyde sensing

Abstract

Degradable electrode materials are needed to reduce the environmental burden associated with disposable electrochemical devices. Herein, a pomelo peel (PP)-supported silver nanowire/multi-walled carbon nanotube (AgNWs/MWNTs) nanocomposite electrode is prepared by alternating drop-casting AgNWs and MWNTs onto the porous albedo of waste pomelo peel. The PP substrate provides a low-cost biomass scaffold with naturally porous structure and oxygen-containing groups, facilitating the anchoring of the conductive nanonetwork. Scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction are used to examine the substrate structure and nanocomposite layer, while electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) are used to evaluate electrode behavior. The AgNWs/MWNT/PP electrode is further assessed for formaldehyde (HCHO) sensing in alkaline medium, showing linear response over 2–70 mM and 0–10 µM, apparent sensitivity of 642 µA mM⁻¹ cm⁻², estimated detection limit of 2.69 µM, relative standard deviation of 4.33, and 91.1% current retention after 20 days. Soil-burial tests show rapid mass loss of the PP-based electrode, with 58.53% residual mass after 3 days and no intact electrode remaining after 33 days. This work highlights a biomass-derived, degradable substrate strategy for nanocomposite electrochemical electrodes.