H2‐Directing Strategy on In Situ Synthesis of Co‐MoS2 with Highly Expanded Interlayer for Elegant HER Activity and its Mechanism

Abstract MoS 2 has drawn great attention as a promising Pt‐substituting catalyst for the hydrogen evolution reaction (HER). This work utilizes H 2 as the structure directing agent (SDA) to in situ synthesize a range of Co‐MoS 2 ‐ n ( n = 0, 0.5, 1.0, 1.4, 2.0) with expanded interlayer spacings ( d = 9.2 – 11.1 Å), which significantly boost their HER activities. The Co‐MoS 2 ‐1.4 with an interlayer spacing of 10.3 Å presents an extremely low overpotential of 56 mV (at 10 mA cm −2 ) and a Tafel slope of 32 mV dec −1 , which is superior than most reported MoS 2 ‐based catalysts. Density function theory calculations are used to gain insights that i) the H 2 can be dissociatively adsorbed on MoS 2 and greatly affect the related surface free energy by regulating the interlayer spacing; ii) the expanded interlayer spacing can significantly decrease the absolute value of Δ G H , thereby leading to greatly promoted HER activity. Additionally, the large amounts of 1T phase (73.9–79.2%) and Co‐Mo‐S active sites (40.9–91.3%) also contribute to the enhanced HER activity of the synthesized samples. Overall, a simple new strategy for in situ synthesis of Co‐MoS 2 with an expanded interlayer spacing is proposed, which sheds light on other 2D energy material designs.