Rational Integration of ZIF-8 and BiPO4for Energy Storage and Environmental Applications

Abstract

Environmental pollution and energy storage are among the most pivotal challenges of today's world. The development of multifunctional materials is required to address these challenges. Our study presents the rational design and synthesis of a hybrid material (ZIF-8@BiPO4) with dual functionality: an outstanding supercapacitor electrode and an excellent photocatalyst. The ZIF-8@BiPO4hybrid structure was obtained by conjoining zinc ions and 2-methylimidazole ligands toward BiPO4by a one-pot stirring route at room temperature. The ZIF-8@BiPO4resulted in considerably higher specific capacitance (Cs) (489 F g-1at a scan rate of 5 mV s-1497 F g-1at a current density of 1 A g-1) than that of pure BiPO4(358; 443 F g-1) and ZIF-8 (185; 178 F g-1) under the same conditions in a three-electrode cell using the 2 M KOH aqueous electrolyte. Afterward, an asymmetric supercapacitor (ASC) device was fabricated with BiPO4as the anode and ZIF-8@BiPO4as the cathodes, acquiring an outstanding Cs of 255 F g-1at a current density of 0.5 A g-1with significant cycling stability (81% over 10,000 cycles). Moreover, the ASC has an energy density of 17.5 Wh kg-1and a power density of 13,695 W kg-1, which can be considered to be at the borderline between batteries and supercapacitors. The photocatalytic activity of ZIF-8@BiPO4was further studied using a methylene blue (MB) dye and sildenafil citrate (SC) drug-active molecules. The degradation of MB was approximately 78% through the photocatalytic reduction after 180 min of UV irradiation. The outstanding characteristics together with the ecofriendly and low-cost preparation make ZIF-8@BiPO4appealing for a broad range of applications.