In‐Situ Pt‐Decorated, Direct Growth of Mixed Phase <scp>2H</scp>/<scp>1T</scp>–<scp>MoSe₂</scp> on Carbon Paper for Enhanced Hydrogen Evolution Reaction

Metal dichalcogenide‐based 2D materials, gained considerable attention recently as a hydrogen evolution reaction (HER) electrocatalyst. In this work, we synthesized MoSe 2 ‐based electrocatalyst via hydrothermal route with varying phase contents (1T/2H) and respective HER performances were evaluated under the acidic media (0.5 m H 2 SO 4 ), where best HER performance was obtained from the sample consisting of mixed 1T/2H phases, which was directly grown on a carbon paper (167 mV at 10 mA cm −2 ) Furthermore, HER performance of electrocatalyst was further improved by in‐situ electrodeposition of Pt nanoparticles (0.15 wt%) on the MoSe 2 surface, which lead to significant enhancement in the HER performances (133 mV at 10 mA cm −2 ). Finally, we conducted density functional theory calculations to reveal the origin of such enhanced performances when the mixed 1T/2H phases were present, where phase boundary region (1T/2H heterojunction) act as a low energy pathway for H 2 adsorption and desorption via electron accumulation effect. Moreover, presence of the Pt nanoparticles tunes the electronic states of the MoSe 2 based catalyst, resulting in the enhanced HER activity at heterointerface of 1T/2H MoSe 2 while facilitating the hydrogen adsorption and desorption process providing a low energy pathway for HER. These results provide new insight on atomic level understanding of the MoSe 2 based catalyst for HER application.