Phosphonate-Derived Nanoporous Metal Phosphates and Their Superior Energy Storage Application

Nanoporous nickel, aluminum, and zirconium phosphates (hereafter, abbreviated as NiP, AlP, and ZrP, respectively) with high surface areas and controlled morphology and crystallinity have been synthesized through simple calcination of the corresponding phosphonates. For the preparation of phosphonate materials, nitrilotris(methylene)triphosphonic acid (NMPA) is used as phosphorus source. The organic component in the phosphonate materials is thermally removed to form nanoporous structures in the final phosphate materials. The formation mechanism of nanoporous structures, as well as the effect of applied calcination temperatures on the morphology and crystallinity of the final phosphate materials, is carefully discussed. Especially, nanoporous NiP materials have a spherical morphology with a high surface area and can have great applicability as an electrode material for supercapacitors. It has been found that there is a critical effect of particle sizes, surface areas, and the crystallinities of NiP materials toward electrochemical behavior. Our nanoporous NiP material has superior specific capacitance, as compared to various phosphate nanomaterials reported previously. Excellent retention capacity of 97% is realized even after 1000 cycles, which can be ascribed to its high structural stability.