  Transition metal dichalcogenides like MoS2 can exist many phases like the
semiconducting 2H and the metallic 1T phases which have shown intriguing
properties for energy and electrocatalytic applications. However, the 2H and 1T
phases normally distribute coherently in a single-layered MoS2 sheet which is
accompanied with ubiquitous hetero-phase boundaries. In this work, by using
density functional theory and electrochemical measurement, we report strong
charge transfer ability between 2H/1T phase boundary of MoS2 and graphene which
accounts for a superb coexistence of gravimetric and volumetric capacitances of
272 F g-1 and 685 F cm-3. As a proof-of-concept application, a flexible
solid-state asymmetric supercapacitor based on MoS2/graphene is fabricated,
showing a remarkable energy and power densities (46.3 mWh cm-3 and 3.013
Wcm-3). Our work shows the promise of promoting the efficiency of charge flow
and energy storage through engineering phase boundary and interface in
phase-change materials.
