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 Mo₂ C nanoparticles supported on carbon sheets (Mo₂ C/CS) was designed toward overall water splitting. Owing to the highly active catalytic nature of Mo₂ C 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 Mo₂ C/CS catalyst as both anode and cathode electrodes. Such high performance makes Mo₂ C/CS a promising electrocatalyst for practical hydrogen production from water splitting.