LAUSR

MoS2 becomes an efficient and durable nonprecious-metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T-phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2 -based catalysts targeting only a single or few of these characteristics, the all-in-one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A-MoS2 ) that predominantly comprises 1T-MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A-MoS2 results in the removal of intercalated NH3 and H2 S to form an all-in-one MoS2 with multifunctional active sites mentioned above (R-MoS2 ) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2 -based electrocatalysts. In particular, a hybrid MoS2 /nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high-current region (>25 mA cm-2 ), demonstrating that R-MoS2 -based materials can potentially replace Pt catalysts in practical alkaline HER systems.