A highly sensitive electrochemical sensor based on a composite of two-dimensional (2D) reduced graphene oxide (rGO) and three-dimensional (3D) zeolitic imidazolate framework-8 (ZIF-8) for detecting the NH4+ ion is reported. The ZIF-8/rGO composite electrode is in situ grown to be anchored on the Si/Ag substrate. Here, the rGO layer has high conductivity, while ZIF-8 has a large specific surface area, which provides a large number of active sites. This structure significantly increases the electrical conductivity and enhances the electrochemical performance. With a differential pulse voltammetry measurement at the pH value of 7.00, the multidimensional composite electrode with the optimal ZIF-8 structure exhibits a sensitivity of 9.30 μA μM–1, and a detection range of 5–50 μM with a low detection limit of 3.00 × 10–9 M, as well as high repeatability, stability, and selectivity. These results might be due to the oxidation reaction of NH4+ with the ZIF-8 framework and the special 2D–3D electron transfer channel formed by the composite.
Graphical We propose a one–step hydrothermal synthesis method to regulate the lattice NH 4 + ion content in vanadium oxide materials and discover varied lattice NH 4 + content could affect the structural evolution and electrochemical performance of the material, and our work will provide a new route for designing high performance vanadium oxide cathode materials in aqueous zinc ion batteries. Aqueous zinc ion batteries have been extensively researched due to their distinctive advantages such as low cost and high safety. Vanadium oxides are important cathode materials, however, poor cycle life caused by vanadium dissolution limits their application. Recent studies show that the lattice NH 4 + in vanadium oxides can act as a pillar to enhance structural stability and play a crucial role in improving its cycling stability. Nevertheless, there is still a lack of research on the effect of the lattice NH 4 + content on structural evolution and electrochemical performance. Herein, we synthesize vanadium oxides with different contents of lattice NH 4 + by a one-step hydrothermal reaction. The vanadium oxides with lattice NH 4 + exhibit high initial capacity, as well as good cycling stability and rate performance compared to bare vanadium oxide. Combined with electrochemical analyses, ex-situ structural characterizations, and in-situ X-ray diffraction tests, we reveal that the lattice NH 4 + content plays a positive role in vanadium oxides′ structural stability and cation diffusion kinetics. This work presents a direction for designing high–performance vanadium cathodes for aqueous zinc ion batteries.
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