Two-dimensional MXene Assisted Preparation Of High Performance Catalysts For Hydrogen Production From Alkaline Electrolysis Of Water

Hydrogen production from alkaline water electrolysis is one of the most effective ways to realize green hydrogen.However,at present,the main bottleneck of hydrogen production from industrial electrolysis of water requires high cell voltage.At present,most catalysts can not be suitable for industrial application requirment.Therefore,the design of high efficient and stable electrocatalyst to reduce the cell voltage is the key to realize large-scale hydrogen production from alkaline water electrolysis.In this work,in order to prepare high performance catalytic electrode operating stably at high current density,the modification method of regulating the interface property of two-dimensional material MXene was studied and explored the preparation method of nanosheet arrays loading active metal catalyst assisted by MXene.The electrochemical performance of a series of catalysts for hydrogen production by alkaline water electrolysis was also evaluated;In addition,the structural evolution of three kinds of catalysts prepared with MXene assistance during the water splitting was revealed,and the design and preparation method of high-efficiency catalyst for hydrogen production from alkaline water electrolysis under high current density were obtained.The main research contents include:（1）The interface of 2D material MXene（Ti₃C₂）is modified by cetyltrimethylammonium bromide（CTAB）,and the interlayer spacing of Ti₃C₂ is expanded,accelerating the electron transfer of modified Ti₃C₂（c-Ti₃C₂）.In this section,a Ru/c-Ti₃C₂/NF 3D electrode,featuring both superhydrophilicity and superaerophobicity,is synthesized on porous Ni foam,achieving low overpotential at high current density.The Ru/c-Ti₃C₂/NF can drive the current densities of 10,100,500,1000 m A cm^-2 at overpotentials of 37,113,219 and 320 m V,respectively,for hydrogen evolution reaction（HER）in 1.0 M KOH.It remains stable at 100 m A cm^-2 during continuous electrolysis of 12 h.In combination with characterization results and DFT calculation,it is found that the modified c-Ti₃C₂ has obvious advantages in the adsorption and dissociation of water.Ru/c-Ti₃C₂/NF electrode can promote the dissociation of water and the production of hydrogen intermediates（H^*）in alkaline media,providing more H^*for Ru absorption/desorption of H^*.Therefore,the prepared Ru/c-Ti₃C₂/NF electrode exhibits rapid water dissociation ability to produce hydrogen in alkaline media.（2）Based on the interfacial adsorption and induced nucleation characteristics of Ti₃C₂,a simple synthesis method by electrodepositation-hydrothermal process is developed to prepare Ni（OH）₂ nanosheet arrays loading with Pt nanoparticles on porous nickel foam（Pt/TiO₂/Ni（OH）₂/NF）.It is worth noting that the Pt/TiO₂/Ni（OH）₂/NF electrode with interconnected arrays exhibits noticeable HER performance,achieving ultralow overpotentials of 107,145 and 184 m V at high current densities of 500,1000and 1500 m A cm^-2,respectively,which outperforms most reported HER electrocatalysts.Additionally,Pt/TiO₂/Ni（OH）₂/NF electrode shows outstanding electrochemical durability at high current density of 1400 m A cm^-2 at least 12 h.As a bifunctional catalyst,Pt/TiO₂/Ni（OH）₂/NF electrode requires only 1.83 and 1.95 V to drive 500 and1000 m A cm^-2,respectively,towards full water electrolysis along with considerable stability at least 25 h.In situ Raman spectroscopy results indicate that the the synergy of Pt and TiO₂/Ni（OH）₂ mainly contributes to the enhanced HER performance.Meanwhile,the synergy of PtO_x and Ni OOH species generated by surface reconstruction of Pt/TiO₂/Ni（OH）₂ improves the alkaline oxygen evolution reaction（OER）activity.DFT results show that the TiO₂/Ni（OH）₂ matrix accelerates the water adsorption and activation due to the low water dissociation energy barriers,promoting more H^*intermediates production,synergistically improving the HER activity.（3）In order to further improve the OER activity of the catalyst,an ultra-high alkaline OER active electrode（Fe₂O₃/Ni（OH）₂/NF）is prepared on Ni（OH）₂/NF nanoarrays prepared by Ti₃C₂.Accordingly,the optimized Fe₂O₃/Ni（OH）₂/NF exhibits excellent OER performances with ultra-low overpotentials of 291,319 and 341 m V at industrial current densities of 500,1000,1500 m A cm^-2and exceptional long-term stability over 17 h at a ultrahigh current density of 1300 m A cm^-2in alkaline condition.Particularly,in situ Raman spectroscopy results reveal the active center changed from Fe₂O₃ and Ni（OH）₂ to highly active Fe OOH and Ni OOH due to the self-reconstruction on the surface of Fe₂O₃/Ni（OH）₂,thus improving the OER activity of the catalyst.DFT calculations show that the heterojunction composed of Fe OOH and Ni OOH could optimize the adsorption energy of the reaction intermediates and provide more active sites for OER process.