Bifunctional water splitting enhancement by manipulating Mo-H bonding energy of transition Metal-Mo2C heterostructure catalysts

Molybdenum carbide (Mo2C) exhibits unique competitive advantages in electrochemical water splitting due to its physicochemical properties. The high intrinsic activity is essential for the high-efficient Mo2C catalysts. Herein, transition metal (Ni, Co, or Fe)-Mo2C-embedded in N-doped carbon sheets grown on Ni foam (TM/Mo2C-NCSs) are synthesized to enhance the intrinsic activity of Mo2C by optimizing the Mo-H bonding energy through the interfacial interactions between Ni, Co, or Fe, and Mo2C. Owing to the superior intrinsic activity, fast ternary channels, and abundant active sites, the Ni/Mo2C-NCSs possess the lowest overpotential for HER (131 mV) and the Fe/Mo2C-NCSs show the lowest overpotential for OER (293 mV) at a current density of 100 mA cm−2 in 1 M KOH. The results analyzed with the Density function theory (DFT) calculation indicate that the most superior H adsorption site is at the interface between Mo2C and Ni hybrid. H was adsorbed on interface Mo&[email protected]/Mo2C with proper hydrogen adsorption free energies (ΔGH*), achieving a fast desorption process in HER. This mechanism is absent in the pristine Mo2C catalysts. An alkaline electrolyzer with a cathode of Ni/Mo2C-NCSs and anode of Fe/Mo2C-NCSs demonstrates a small voltage of 1.66 V at a current density of 100 mA cm−2. This work offers an elaborated strategy of interface engineering to enhance the intrinsic catalytic activity of Mo2C by accelerating H2 desorption in HER and enhancing the catalytic kinetics of OER simultaneously.