A Universal Strategy for Intimately Coupled Carbon Nanosheets/MoM Nanocrystals (M = P, S, C, and O) Hierarchical Hollow Nanospheres for Hydrogen Evolution Catalysis and Sodium-Ion Storage.

Intimately coupled carbon/transition-metal-based hierarchical nanostructures are one of most interesting electrode materials for boosting energy conversion and storage applications owing to the strong synergistic effect between the two components and appealing structural stability. Herein, a universal method is reported for making hierarchical hollow carbon nanospheres (HCSs) with intimately coupled ultrathin carbon nanosheets and Mo-based nanocrystals. The in situ and confined reaction of the synthetic strategy can not only allow the aggregation of the nanocrystals to be impeded, but also endows extremely intimate coupled interaction between the conductive carbon nanosheets and the nanocrystals MoM (M = P, S, C and O). As a proof of concept, the as-prepared MoP/C HCSs exhibit extraordinary hydrogen evolution reaction electrocatalytic activity with small overpotential and robust durability in both acidic and alkaline solutions. In addition, the unique sheet-on-sheet MoS2 /C HCSs as an anode demonstrate high capacity, great rate capabilities, and long-term cycles for sodium-ion batteries (SIBs). The capacity can be maintained at 410 mA h g-1 even after 1000 cycles even at a high current density of 4 A g-1 , one of the best reported values for MoS2 -based electrode materials for SIBs. The present work highlights the importance of designing and fabricating functional strongly coupled hybrid materials for enhancing energy conversion and storage applications.