Aerosol synthesis of molybdenum diselenide–reduced graphene oxide composite with empty nanovoids and enhanced hydrogen evolution reaction performances

MoSe₂–reduced graphene oxide (rGO) composite powders with unique structures containing empty nanovoids and excellent hydrogen evolution reaction (HER) performances were prepared using a pilot-scale spray-drying process. One-step post-treatment of the spray-dried powders produced the macroporous MoSe₂–rGO composite with empty nanovoids through an intermediate MoO₃–Se–GO composite. Ultrafine MoSe₂nanocrystals, which consisted of a few layers and were several nanometers in size, were uniformly dispersed on the surfaces of the MoSe₂–rGO composite powders with the optimal rGO contents. The MoSe₂–rGO–M composite (20 wt% rGO) had the optimized porous structure with a uniform distribution of MoSe₂nanocrystals and enough the rGO content for a fast electron transport, and thus exhibited the highest HER activity. The MoSe₂–rGO–M composite powders exhibited a current density of 10 mA cm⁻²at a small overpotential of 0.21 V, which was lower than that of bare MoSe₂(10 mA cm⁻²at 0.31 V). The Tafel slopes for bare MoSe₂and MoSe₂–rGO–M composite powders were 120 and 57 mV dec^–1, respectively. The synergistic effects of rGO sheets and MoSe₂nanocrystals and the unique porous structure resulted in outstanding HER performance with a small Tafel slope and overpotential.