1T‐Rich MoS ₂ and Its Enhanced Hydrogen Evolution Reaction (HER) Activity by Functionalization With Organic Ammonium Cations

ABSTRACT Molybdenum disulfide (MoS 2 ), specifically in its 1T‐phase, is of significant interest as a catalyst for the hydrogen evolution reaction (HER) via water splitting. However, 1T‐MoS 2 is metastable and gradually converts to the thermodynamically stable but less catalytically active 2H‐phase, leading to a marked decline in HER activity. In this work, we demonstrate that functionalization with anilinium (ANI) monocation and para ‐phenylenediammonium (PPDA) dication can effectively stabilize 1T‐MoS 2 . The powder X‐ray diffraction, electron microscopy, and Raman spectroscopy data confirm that as‐synthesized ANI@1T‐MoS 2 and PPDA@1T‐MoS 2 samples retain a significant fraction of 1T‐phase over time. These catalysts exhibit hydrogen evolution rates of 5.7 and 4.6 mmol g −1 h −1 of H 2 , respectively, which are significantly higher than that of 2H‐MoS 2 (1.7 mmol g −1 h −1 ) and are close to the activity of as‐made 1T‐MoS 2 (10.9 mmol g −1 h −1 ). These results suggest successful stabilization of 1T‐MoS 2 and offer a valuable strategy for simultaneously enhancing both stability and catalytic activity.