Kwak, In Hye Kwon, Ik Seon Abbas, Hafiz Ghulam Seo, Jaemin Jung, Gabin Lee, Yeron Kim, Doyeon Ahn, Jae-Pyoung Park, Jeunghee Kang, Hong Seok 2024-01-19T21:00:42Z 2024-01-19T21:00:42Z 2022-01-25 2019-02 2050-7488 https://pubs.kist.re.kr/handle/201004/120390 Two-dimensional layered MoS2 has recently been considered as an excellent catalyst for the water-splitting hydrogen evolution reaction (HER). Herein, we synthesize 1T' phase MoS2 that was intercalated with a series of alkylated p-phenylenediamines (PDs). The substituted N atoms produced S vacancies, leading to a composition of MoS2-2xNx (x = 0.1). The more abundant methyl groups induce a larger charge transfer, resulting in excellent HER performance: for tetramethyl PD, the overpotential is 0.15 V at 10 mA cm(-2) with a Tafel slope of 35 mV dec(-1). The catalytic activity of the complexes depends on the concentration of the intercalated molecules, showing an optimum at a concentration of 8 mol%. First-principles calculations showed that the intercalated complexes (1T' phase) having N atom-S vacancy (N-VS) pairs are stabilized by a large charge transfer from the PD molecules that is enhanced by the methyl groups (i.e., 0.40e-0.84e per molecule at 6.25 mol% intercalation). The charge transfer increases the density of states at and just above the Fermi level, thereby increasing the electron concentration at low cathodic bias. The active sites for the Volmer reaction are found to be N atoms in the proximal N-VS pairs. The activation barrier for the Heyrovsky reaction becomes higher at higher concentrations of the intercalants, suggesting that the experimental HER performance is also kinetically controlled. English ROYAL SOC CHEMISTRY Intercalated complexes of 1T '-MoS2 nanosheets with alkylated phenylenediamines as excellent catalysts for electrochemical hydrogen evolution Article 10.1039/c8ta11085a 1 JOURNAL OF MATERIALS CHEMISTRY A, v.7, no.5, pp.2334 - 2343 JOURNAL OF MATERIALS CHEMISTRY A 7 5 2334 2343 N scie scopus 000457546000041 2-s2.0-85060813355 Chemistry, Physical Energy & Fuels Materials Science, Multidisciplinary Chemistry Energy & Fuels Materials Science Article ACTIVE EDGE SITES MOS2 NANOSHEETS MOLYBDENUM-DISULFIDE SULFUR VACANCIES TRANSITION ELECTROCATALYSTS PHASE GENERATION 1T-MOS2 PLANE