Phase Engineered MoSe₂/MoO₃ Composite with Improved Hydrogen Evolution Reaction

Maximization of the electrocatalytic performance of transition-metal dichalcogenides (TMDCs) and their composites with other nanostructured materials requires development of a suitable synthesis strategy and phase engineering and subsequently their intercoupling with the defects. Herein, we report a facile hydrothermal approach for the synthesis of mixed-phase (1T-2H) MoSe 2 and its composite with MoO 3 . Systematically varying the reaction temperature followed by structural analysis revealed a kinetically controlled synthesis regime in which MoSe 2 with the highest metallic (1T) content of 65% was obtained. In addition to the highly conducting metallic 1T-phase, the electronically coupled interfaces of MoSe 2 and MoO 3 composite together with defects and active edge sites significantly contributed to the improved hydrogen evolution reaction (HER) performance. As a result, the obtained MoSe 2 /MoO 3 electrocatalyst exhibited a significantly lower overpotential (94 mV at 10 mA/cm –2 ) and lower Tafel slope (62 mV/dec) compared with 1T-phase enriched MoSe 2 (150 and 89 mV/dec, respectively) and 2H-phase enriched MoSe 2 (200 and 163 mV/dec). Overall, the MoSe 2 /MoO 3 composite has shown highly stable operation with a very small change (less that 2%) in current retention for continuous operation of more than 15 hours. The present work demonstrated a controlled and facile approach for the synthesis of highly efficient MoSe 2 /MoO 3 -based electrocatalysts with high yield of conducting 1T-phase, defects, selenium vacancies, and highly active edge terminated surfaces. These features make the electrocatalyst highly beneficial for HER kinetics, and the method can be easily extended to other transition-metal-based composites.