Enhanced thermal stability and excellent electrochemical and photocatalytic performance of needle-like form of zinc-phthalocyanine

This study proposes enhanced thermal stability and excellent electrochemical and photocatalytic performance of hierarchical structure of zinc-phthalocyanine (ZnPc) samples prepared through eco-friendly enhanced microwave (MW) synthesis over 5 min at T = 200 °C. The structure and morphology of the obtained ZnPc were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (TEM), and Atomic Force Microscope (AFM). At the same time, thermal stability was analyzed using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The obtained ZnPc with high crystallinity, pure crystalline phases and reflection peaks related to the β-form of ZnPc. The average crystallite size (D) of 74 nm was determined using the Debye-Scherrer equation for a peak at 2θ = 9.30°. AFM image presented ZnPc material as a distinguished multilayered crystal with a rhombus-shaped crystal structure that seems very smooth on its surface, while TEM images showed a hierarchical structure of synthesized ZnPc self-organized assembles from the needle-like morphology which are aligned at different orientations having length up to approximately 500 nm and with 20 nm in diameter. TGA and DTA showed that the decomposition process occurred at a high temperature of 649 °C, for a heating rate of 15 °C/min, indicating good thermal stability of the investigated ZnPc. The photocatalytic activity of the hierarchically structured ZnPc was evaluated using different initial concentrations of Reactive Blue 19 (RB-19), pH value, and catalyst dose. Additionally, the electrochemical performance of ZnPc as electrode material was investigated. This study indicates facile, low-cost, and green MW method can be used for the preparation of the needle-like form of ZnPc as a promising multifunctional material for the potential applications: in thermal energy storage in future solar power technologies, as electrode material exhibiting superior voltammetric response, with cathodic and anodic current values and as photocatalyst for degradation of RB-19 and other organic dye-pollutants.