Mo‐Based Ultrasmall Nanoparticles on Hierarchical Carbon Nanosheets for Superior Lithium Ion Storage and Hydrogen Generation Catalysis

Constructing 3D hierarchical architecture consisting of 2D hybrid nanosheets is very critical to achieve uppermost and stable electrochemical performance for both lithium‐ion batteries (LIBs) and hydrogen evolution reaction (HER). Herein, a simple synthesis of uniform 3D microspheres assembled from carbon nanosheets with the incorporated MoO 2 nanoclusters is demonstrated. The MoO 2 nanoclusters can be readily converted into the molybdenum carbide (Mo 2 C) nanocrystals by using high temperature treatment. Such assembling architecture is highly particular for preventing Mo‐based ultrasmall nanoparticles from coalescing or oxidizing and endowing them with rapid electron transfer. Consequently, the MoO 2 /C hybrids as LIB anode materials deliver a specific capacity of 625 mA h g −1 at 1600 mA g −1 even after 1000 cycles, which is among the best reported values for MoO 2 ‐based electrode materials. Moreover, the Mo 2 C/C hybrids also exhibit excellent electrocatalytic activity for HER with small overpotential and robust durability in both acid and alkaline media. The present work highlights the importance of designing 3D structure and controlling ultrasmall Mo‐based nanoparticles for enhancing electrochemical energy conversion and storage applications.