Molybdenum Carbide‐Oxide Heterostructures: In Situ Surface Reconfiguration toward Efficient Electrocatalytic Hydrogen Evolution

Abstract Heterostructured Mo 2 C‐MoO x on carbon cloth (Mo 2 C‐MoO x /CC), as a model of easily oxidized electrocatalysts under ambient conditions, is investigated to uncover surface reconfiguration during the hydrogen evolution reaction (HER). Raman spectroscopy combined with electrochemical tests demonstrates that the Mo VI oxides on the surface are in situ reduced to Mo IV , accomplishing promoted HER in acidic condition. As indicated by density functional theoretical calculations, the in situ reduced surface with terminal Mo=O moieties can effectively bring the negative Δ G H* on bare Mo 2 C close to a thermodynamic neutral value, addressing difficult H* desorption toward fast HER kinetics. The optimized Mo 2 C‐MoO x /CC only requires a low overpotential ( η 10 ) of 60 mV at −10 mA cm −2 in 1.0 m HClO 4 , outperforming Mo 2 C/CC and most non‐precious electrocatalysts. In situ surface reconfiguration are shown on W 2 C‐WO x , highlighting the significance to boost various metal‐carbides and to identify active sites.