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

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