1T'MoTe₂-based On-chip Electrocatalytic Microdevice:a Platform To Unravel Oxidation-dependent Electrocatalysis

Ultrathin layered transition metal dichalcogenides?TMDs?are of particular interest as low-cost alternatives to highly active electrocatalysts because of their high surface activation energy.However,their striking structural characteristics will undoubtedly cause chemical instability,and they undergo oxidation extremely easily under normal circumstances.Establishing a clear material model for unraveling intrinsic or/and oxidation-dependent electrocatalysis is of great importance for designing more efficient electrocatalysts.We designed and fabricated an on-chip microcell that uses an individual nanosheet as the working electrode to evaluate the contribution of a single factor?the oxidation behavior?to hydrogen evolution reaction?HER?performance.Moreover,O₂ plasma technology was utilized to accurately control the degree of oxidation by the processing t ime.Specifically,taking a 1T'-MoTe₂ ultrathin nanosheet as a prototype,the lower onset overpotential and activation energy?E_a?of adequately oxidized MoTe₂ demonstrates that the HER performance was optimized obviously with some degree of oxidation.With the aid of advanced characterization and theoretical simulation,the incorporated oxygen during the oxidation process was used as an electron density modulator to manipulate the electron densities and contribute to the enriched surface charge and lower Gibbs reaction energy for high-performance electrocatalysis.This work provides atomic-level insights into the role of surface oxide in ultrathin TMDs HER catalysis by an on-chip electrocatalytic microdevice and the first semiquantification of the model-structure-performance relationship,opening the door for designing catalytic centers.