Mesoporous reduced graphene oxide/WSe2 composite particles for efficient sodium-ion batteries and hydrogen evolution reactions

Mesoporous WSe2-reduced graphene oxide (WSe2-rGO) composite particles were prepared by spray pyrolysis and subsequent selenization. The WSe2-rGO composite particles had both well-dispersed rGO nanosheets and well-faceted WSe2 nanocrystals with plenty of folded edges. As a comparison sample, hierarchical structured WSe2 particles were produced by selenization of the bare WO3 particles obtained by spray pyrolysis. The WSe2-rGO composite particles showed superior electrochemical properties for sodium-ion batteries (SIBs) and electrocatalytic efficiencies for hydrogen evolution reactions (HERs) compared to those of the bare WSe2 particles. The discharge capacities of the WSe2-rGO composite particles and bare WSe2 particles for the 100th cycle at a current density of 0.5 A g(-1) for sodium-ion storage were 238 and 36 mA h g(-1), respectively; their corresponding capacity retentions measured from the third cycle were 80% and 13%. The WSe2-rGO composite particles showed much lower onset potential and larger current density (36.5 mA cm(-2) at eta = 300 mV) than those of the bare WSe2 particles (0.61 mA cm(-2) at = 300 mV). The Tafel slopes for the WSe2-rGO composite and bare WSe2 particles were approximately 60 and 115 mV dec(-1), respectively.