Single‐atom‐layer catalysis in MoS2 monolayer activated by long‐range ferromagnetism: beyond the single‐atom catalysis

Single-atom-layer catalysts with fully activated basal-atoms will provide an ultimate solution to the low loading-density bottleneck of single-atom catalysts. Herein, we propose a strategy to activate the majority of basal sites of monolayer MoS 2 , by doping Co ions to induce long-range ferromagnetic order. This strategy, as revealed by in-situ synchrotron radiation microscopic infrared spectroscopy and electrochemical measurements, could activate more than 50% of the originally inert basal-plane S atoms in the ferromagnetic monolayer for the hydrogen evolution reaction. Consequently, on a single monolayer of ferromagnetic MoS 2 measured by on-chip micro-cell, a current density of 10 mA cm -2 could be achieved at the overpotential of 137 mV, corresponding to a mass activity of 28, 571 A g -1 , which is two orders of magnitude higher than the multilayer counterpart. The exchange current density of 75 μA cm -2 for the monolayer also surpasses most of other MoS 2 -based catalysts reported so far. Experimental characterizations and theoretical calculations unravel that the activation of basal plane S atoms is due to the delocalization of spin states of d -electron and the increase of S- p electronic density around the Fermi level, and hence promotes the H adsorption ability of basal-plane S atoms.