Strongly Coupled Molybdenum Carbide on Carbon Sheets as a Bifunctional Electrocatalyst for Overall Water Splitting

High-performance and affordable electrocatalysts from earth-abundant elements are desirably pursued for water splitting involving hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here, a bifunctional electrocatalyst of highly crystalline Mo2C nanoparticles supported on carbon sheets (Mo2C/CS) was designed toward overall water splitting. Owing to the highly active catalytic nature of Mo2C nanoparticles, the high surface area of carbon sheets and efficient charge transfer in the strongly coupled composite, the designed catalysts show excellent bifunctional behavior with an onset potential of -60 mV for HER and an overpotential of 320 mV to achieve a current density of 10 mA cm(-2) for OER in 1 M KOH while maintaining robust stability. Moreover, the electrolysis cell using the catalyst only requires a low cell voltage of 1.73 V to achieve a current density of 10 mA cm(-2) and maintains the activity for more than 100 h when employing the Mo2C/CS catalyst as both anode and cathode electrodes. Such high performance makes Mo2C/CS a promising electrocatalyst for practical hydrogen production from water splitting.