α-MoB2 Nanosheets for Hydrogen Evolution in Alkaline and Acidic Media

α-MoB2 is recognized as the most efficient molybdenum boride for electrocatalytic hydrogen evolution reaction (HER). However, the convenient synthesis of single phase α-MoB2 is still challenging, and its HER activity in alkaline electrolytes remains unclear. Herein, we report the first successful synthesis of the α-MoB2 nanosheets by a simple and facile molten salt method through the MoCl5 and NaBH4 reaction at 850 °C. The α-MoB2 nanosheets exhibit a remarkable HER performance in alkaline electrolytes, delivering a low overpotential of 124 mV at a current density of 10 mA/cm2. In acidic electrolytes, an improved performance was found in comparison to that of the bulk and nano α-MoB2 with an overpotential as low as 141 mV at 10 mA/cm2. Such HER performance arises from the nanosheet structure that allows more active planes to be exposed. In addition, the α-MoB2 nanosheets possess an outstanding stability in both acidic and alkaline media, showing negligible current density drop even after 3000 cycles and more than 24 h of potentiostatic operation.