[Mo S ] as a Model System for Hydrogen Evolution Catalysis by MoS : Probing Protonation Sites in the Gas Phase by Infrared Multiple Photon Dissociation Spectroscopy.

Materials based on molybdenum sulfide are known as efficient hydrogen evolution reaction (HER) catalysts. As the binding site for H atoms on molybdenum sulfides for the catalytic process is under debate, [HMo S ] is an interesting molecular model system to address this question. Herein, we probe the [HMo S ] cluster in the gas phase by coupling Fourier-transform ion-cyclotron-resonance mass spectrometry (FT-ICR MS) with infrared multiple photon dissociation (IRMPD) spectroscopy. Our investigations show one distinct S-H stretching vibration at 2450 cm . Thermochemical arguments based on DFT calculations strongly suggest a terminal disulfide unit as the H adsorption site.