Novel hierarchical nanoporous graphene nanoplatelets with excellent rate capabilities produced via self-templating liquid metal dealloying

A wide variety of multiscale porous carbon materials with improved electrochemical properties have been developed through molecular design, pore control, and compositional tailoring. However, conventional templating and activation approaches involve several time-consuming processes on a limited scale, and the presence of micropores, which act as trap sites, hinders the electrolyte penetration and deteriorates cycle performance in lithium-ion insertion. In this work, hierarchical nanoporous graphene nanoplatelets (HNGNPs) with three-dimensional interconnected meso- and macroporous structure are synthesized by liquid metal dealloying (LMD). These unique porous structures are produced via self-templating dealloying during consecutive two-step dealloying reactions in Bi and Ag melts. The optimized microstructural characteristics of the HNGNPs include high crystallinity (interlayer distance of the (002) plane of ∼0.341 nm and intensity ratio of the Raman G- and D-bands of ∼0.552) and a moderate specific surface area (∼152.7 m² g⁻¹). The high crystallinity of the HNGNPs at a low temperature of 1200 °C results from a catalytic effect of the liquid melt and the accelerated surface diffusion during LMD. The large surface area, high crystallinity, and structural robustness of the mutually interconnected hierarchies of the HNGNPs lead to their excellent rate capabilities and cycling stability in lithium-ion batteries.