Ag-Embedded Hollow Poly(o-phenylenediamine)-Reinforced NiOOH–BiOCl Hybrid-Structured Nanomaterials for Highly Sensitive Dual Electrocatalysis

The rational development of electrodes for electrochemical sensors has wider application prospects in the fields of wearable electronics, environmental monitoring, and medicine. However, it is highly challenging to construct an electrode with high sensitivity and selectivity due to the complex analytical matrices and low concentrations of the targeted compounds. In this study, we rationally designed the Ag-embedded hollow poly(o-phenylenediamine)-reinforced NiOOH-BiOCl (h-APNB) electrocatalyst for dual electrocatalysis toward a biosphere pollutant of 4-nitrophenol (4-NP) and a biomolecule of uric acid (UA). Under optimized conditions, it shows a nanomolar detection limit of 126 pM and 2.3 nM, a high sensitivity of 8.251 and 4.92 μA μM^-1 cm^-2, and linear ranges of 0.001-0.011 and 0.01-1.31 μM for 4-NP and UA, respectively. Owing to its enhanced sensitivity, accuracy, and stability, h-APNB/GCE significantly improved current response with minimal overvoltage for analyte detection. Of interest, the real-sample detection of 4-NP in rainwater and tap water and UA in urine and serum samples is carried out, thereby demonstrating its practical applicability. These hybrid nanostructured electrocatalysts offer significant advantages for sensor applications attributed to the synergism between the electrode/electrolyte interface and electrolyte confinement in the nanomaterial.