Low-temperature selective synthesis of metastable -MoC with electrochemical properties: Electrochemical co-reduction of CO₂ and MoO₃ in molten salts

Metastable molybdenum carbide (alpha-MoC), as a catalyst and an excellent support for metal catalysts, has been widely used in thermo/electro-catalytic reactions. However, the selective synthesis of alpha-MoC remains a great challenge. Herein, a simple one-pot synthetic strategy for the selective preparation of metastable alpha-MoC is proposed by electrochemical co-reduction of CO2 and MoO3 in a low-temperature eutectic molten carbonate. The synthesized alpha-MoC shows a reed flower-like morphology. By controlling the electrolysis time and monitoring the phase and morphology of the obtained products, the growth process of alpha-MoC is revealed, where the carbon matrix is deposited first followed by the growth of alpha-MoC from the carbon matrix. Moreover, by analyzing the composition of the electrolytic products, the formation mechanism for alpha-MoC is proposed. In addition, through this one-pot synthetic strategy, S-doped alpha-MoC is successfully synthesized. Density functional theory (DFT) calculations reveal that S doping enhanced the HER performance of alpha-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption. The present work not only highlights the valuable utilization of CO2 but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.