One-step construction of a transition-metal surface decorated with metal sulfide nanoparticles: A high-efficiency...

Sluggish water dissociation kinetics in the Volmer step is still the huge challenge in designing and synthesizing transition-metal-based electrocatalysts for hydrogen evolution reaction (HER) in alkaline media. Herein, we report a general one-step electrodeposition strategy to construct a high-efficiency electrocatalytic system based on transition metals (Ni, Co and Fe) surface decorated with metal sulfide (Ni₃S₂, Co_xS_y and Fe_xS_y) nanoparticles on Ni foam with thiourea (M_xS_y/M/NF). Evaluated in 1.0 M KOH, the obtained Ni₃S₂/Ni/NF, Co_xS_y/Co/NF and Fe_xS_y/Fe/NF exhibit exceptionally enhanced HER activity, whose overpotentials at 10 mA cm^-2 decrease from 196 to 45 mV, 217 to 89 mV and 288 to 128 mV, respectively, when metal sulfides are introduced to Ni/NF, Co/NF and Fe/NF electrodes. Compared with most of state-of-the-art transition-metal-based catalysts, the Ni₃S₂/Ni/NF electrode displays extremely low overpotential and small Tafel slope (54 mV dec^-1) as well as excellent stability. Further experimental characterizations and density functional theory calculations reveal that such excellent HER performance can be ascribed to the synergetic effect in the combination of metals and metal sulfides, the former of which enhances water dissociation and the latter accelerates hydrogen generation. This intriguing work opens a new avenue towards designing highly active low-cost electrocatalysts for commercial application.