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.