Three-Dimensional Dendritic Structures of NiCoMo as Efficient Electrocatalysts for the Hydrogen Evolution Reaction.

First-row (3d) transition-metal catalysts, such as bimetallic Ni-Co, represent an emerging class of electrocatalysts for HER, but they usually suffer from a large overpotential significantly above thermodynamic demands. Here, we doped NiCo catalyst with non3d metals molybdenum (Mo) for improvement in catalyzing the hydrogen evolution reaction. The ternary catalyst was readily obtained by a one-pot process via the sequential electrodeposition of Ni, Co, and Mo precursors on titanium (Ti) support. By tailing the deposition conditions, we fabricated NiCoMo catalysts with three-dimensional dendritic structures, exhibiting large amounts of electrochemically active sites. To attain the benchmark HER current density of -10 mA cm-2, an overpotential of ∼132 mV is required in 0.1 M KOH for the Mo-doped NiCo (5 atom % Mo in bath), and they produced the decreasing in Tafel slope of ∼108 mV decade-1 exceeding those of binary NiCo alloy catalysts and other contents of Mo doping. In a synergistic effect, dopant incorporation of Mo element may provide near-optimal adsorption energies for HER intermediates promoting the process of water dissociation and hydrogen intermediates production and binding into molecular hydrogen.