Nano-sized ZIF-8 anchored polyelectrolyte-decorated silica for Nitrogen-Rich Hollow Carbon Shell Frameworks toward alkaline and neutral supercapacitors

Abstract

Core-shell hybrid precursors (ZIF-8/PP-SiO2) engineered by zeoliticimidazolate framework (ZIF-8) depositing on the polyelectrolyte-decorated silica (PP-SiO2) are successfully transformed into unusual N-rich hollow carbon shell frameworks (NHCSFs) with adjustable physicochemical properties by the layer-by-layer assembly, interface engineering and subsequent carbonization, which is the first example that systematically elucidates the formation and structure-property correlation of unique three-dimensional (3D) carbon frameworks. The optimal NHCSF-3 displays superior performance with high capacitance approaching 253.6 F g−1 at 1 A g−1, excellent rate capability delivering 79% capacitance retention after a 50-fold increase of the rate, and long lifetime (92.1% retention for 20000 cycles). The studies on alkaline and neutral NHCSF-3//NHCSF-3 supercapacitors demonstrate that the latter with high voltage up to 1.6 V using a Na2SO4 electrolyte can deliver high energy density of 13.3 Wh kg−1. The distinctly enhanced performance illustrates that, except for the factors such as morphology, surface area, pore volume, and N-doping level, hierarchical porosity also significantly boosts electrochemical properties of the materials because of providing efficient charge/mass transport. Overall, this research provides an efficient platform for precisely modulating the structure of MOF-based carbons to develop multifunctional hollow architectures for satisfying enormous demands in upcoming energy devices.