A Green and Fluorine-Free Fabrication of 3D Self-Supporting MXene by Combining Anodic Electrochemical In Situ Etching with Cathodic Electrophoretic Deposition for Electrocatalytic Hydrogen Evolution

The work presents a green and fluorine-free environmentally friendly two-electrode system, which enables the direct fabrication of the corresponding 3D MXene electrodes by the synergistic combination of anodic electrochemical in situ Al etching from Mo2TiAlC2 MAX and cathodic electrophoretic deposition. In just several minutes, the Mo2TiC2 MXene can be deposited on the cathode plate (Pt foil or carbon cloth) without the need for organic large-molecule intercalation agents or ultrasound treatment. This approach allows an efficient separation of MXene from the electrolyte, leading to a significant reduction in the quantity of waste acid generated by conventional acid etching processes. The electrochemically etched-MXene can be uniformly and stably deposited onto carbon cloth (E-MXene@CC), enabling its direct utilization as a 3D electrocatalyst for hydrogen evolution reaction (HER). This unique 3D E-MXene@CC exhibits a moderate HER performance and outperforms most of the reported pure non-precious MXene-based catalysts in 0.5 m H2SO4. In order to clarify the catalytic mechanism, in situ Raman spectroscopy of 3D E-MXene@CC reveals a significant down-shift without observing any new bands when the HER potential shifts negatively, which can be attributed to H+ intercalation.