Single‐Atom‐Layer Catalysis in a MoS2 Monolayer Activated by Long‐Range Ferromagnetism for the Hydrogen Evolution Reaction: Beyond Single‐Atom Catalysis

Abstract Single‐atom‐layer catalysts with fully activated basal‐atoms will provide a solution to the low loading‐density bottleneck of single‐atom catalysts. Herein, we activate the majority of the 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 (HER). 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 Ag −1 , which is two orders of magnitude higher than the multilayer counterpart. Its exchange current density of 75 μA cm −2 also surpasses most other MoS 2 ‐based catalysts. Experimental results and theoretical calculations show the activation of basal plane S atoms arises from an increase of electronic density around the Fermi level, promoting the H adsorption ability of basal‐plane S atoms.