A new form of nanorattle, WS2@WS2 nanorattle, is prepared for the first time by direct sulphidation of pre-synthesised W@WS2 nanorattle template at 350 degrees C. Its microstructural and crystalline structures are characterized, and its electrocatalytic activity and stability in the hydrogen evolution reaction examined. WS2 nanoflakes are formed in-situ from sulphidation of the original W cores, and remain in the final WS2@WS2 nanorattles. They are well dispersed, exposing effectively their edges (catalytically active sites) to the reacting species. Consequently, the as-prepared WS2@WS2 nanorattles exhibit excellent electrocatalytic activity and stability. This finding, along with the novel synthesis technique developed, makes WS2@WS2 nanorattle a very promising electrocatalyst for future hydrogen generation. Furthermore, the synthesis strategy used in this work can be readily extended modified to fabricate other important types of transitional metal nanorattles (e.g., MoS2@MoS2 MoSe2@MoS2 and WC@WS2), potentially benefiting more application areas. (C) 2016 Elsevier B.V. All rights reserved.