Engineering the nanostructure of molybdenum nitride nanodot embedded N-doped porous hollow carbon nanochains for rapid all pH hydrogen evolution

Abstract

Engineering the microstructure at the atomic scale is paramount to developing effective catalysts due to the active sites and mass/charge transfer ability of catalysts severely limited by their microstructure. Herein, we nanoengineer unique necklace-like nanochains composed of molybdenum nitride embedded N-doped carbon, in which the series-wound nanochains are built from hollow beads with a very thin porous wall. MoN nanodots were downsized to 3 nm and uniformly embedded in hollow N-doped porous carbon pearls and wires. The unique hierarchical hollow cavity and ultrathin wall structure of the nanochains offer a high effective reaction chamber, more active sites, and mass/charge transfer for remarkably fast HER. The resultant MoN@NPCNCs exhibit an extremely low HER overpotential of 72 mV at 10 mA cm⁻², a low Tafel slope of 53.21 mV dec⁻¹ in an acidic solution, which is far lower than those of MoN embedded N-doped carbon nanofibers (MoN@NPCNFs, 139.21 mV vs. RHE/82.69 mV dec⁻¹), and other previously reported MoN based catalysts. Density functional theory (DFT) calculations reveal that MoN and N-doped carbon synergistically optimizes the free energy of hydrogen adsorption on the active sites. Furthermore, this catalyst also offers an excellent electrocatalytic ability and durability in both neutral and alkaline media.