MoSe₂ porous microspheres comprising monolayer flakes with high electrocatalytic activity

A facile colloidal route to synthesize MoSe₂ porous microspheres with diameters of 400–600 nm made up of MoSe₂ monolayer flakes (~0.7 nm in thickness) is reported. The solvents trioctylamine (TOA) and oleylamine (OAM) are found to play important roles in the formation of MoSe₂ microspheres, whereby TOA determines the three-dimensional (3D) microspherical morphology and OAM directs the formation of MoSe₂ monolayer flakes. The robust 3D MoSe₂ microspheres exhibit remarkable activity and durability for the electrocatalytic hydrogen evolution reaction (HER) in acid, maintaining a small onset overpotential of ~77 mV and keeping a small overpotential of 100 mV for a current density of 5 mA/cm² after 1, 000 cycles. In addition, similar 3D WSe₂ microspheres can also be prepared by using this method. We expect this facile colloidal route could further be expanded to synthesize other porous structures which will find applications in fields such as in energy storage, catalysis, and sensing.