MoSe2 Embedded CNT-Reduced Graphene Oxide Composite Microsphere with Superior Sodium Ion Storage and Electrocatalytic Hydrogen Evolution Performances.

Highly porous MoSe2-reduced graphene oxide-carbon nanotube (MoSe2-rGO-CNT) powders were prepared by a spray pyrolysis process. The synergistic effect of CNTs and rGO resulted in powders containing ultrafine MoSe2 nanocrystals with a minimal degree of stacking. The initial discharge capacities of MoSe2-rGO-CNT, MoSe2-CNT, MoSe2-rGO, and bare MoSe2 powders for sodium ion storage were 501.6, 459.7, 460.2, and 364.0 mA h g-1, respectively, at 1.0 A g-1. The MoSe2-rGO-CNT composite powders had superior cycling and rate performances compared with the MoSe2-CNT, MoSe2-rGO composite, and bare MoSe2 powders. The electrocatalytic activity of MoSe2-rGO-CNT in the hydrogen evolution reaction (HER) was also compared with that of MoSe2-CNT, MoSe2-rGO, and bare MoSe2. MoSe2-rGO-CNT composite powders exhibited an overpotential of 0.24 V at a current density of 10 mA cm-2, which was less than that of MoSe2-CNT (0.26 V at 10 mA cm-2), MoSe2-rGO (0.32 V at 10 mA cm-2), and bare MoSe2 (0.33 V at 10 mA cm-2). Tafel slopes for the MoSe2-rGO-CNT, MoSe2-CNT, MoSe2-rGO, and bare MoSe2 powders were 53, 76, 86, and 115 mV dec-1, respectively. Because a large electrochemical surface area and ultrafine MoSe2 nanocrystals, the MoSe2-rGO-CNT composite possesses more active sites than the MoSe2-CNT, MoSe2-rGO composite, and bare MoSe2 powders with extensive stacking and large crystalline size, which provide greater catalytic HER activity.