Construction Of Paper-Like Pt/MXene Nanocomposite And Its Hydrogen Evolution Reaction Performance

Hydrogen energy has the characteristics of high combustion calorific value and environmental friendliness,which will occupy a large propotion in the future energy composition,but the key problem that restricts the development of hydrogen energy is the production of hydrogen.Hydrogen evolution reaction（HER）is a half-reaction of electrochemical water splitting,which has faster reaction kinetics and smaller overpotential compared with oxygen evolution reaction.The precious metal platinum has been considered as the benchmark catalyst for HER,however,the scarcity and high price of Pt resources hinder its large-scale application.Reducing the loading and size of Pt is an effective strategy to solve this problem.As the size decreases to the nanometer level,the nanosized Pt will spontaneously agglomerate into large particles,leading to deactivate behavior.Therefore,anchoring the Pt metal source on a suitable substrate can effectively stabilize the sub-nanometer Pt clusters.MXenes,a new class of two-dimensional transition metal carbides and nitrides,have attracted extensive attention due to their unique physicochemical properties,such as high electrical conductivity,strong hydrophilicity,abundant surface functional groups,and diverse synthetic methods.During the preparation process,highly reactive defects are generated on the MXene surface,providing ideal sites for the anchoring of Pt atoms.However,the relatively high surface energy and strong interlayer van der Waals forces of MXene nanosheets lead to spontaneous stacking behavior,resulting in the coverage of the active centers of the catalyst.Based on the aforementioned background,MXene nanosheets with a few-layer structure and Pt source were used to construct a three-dimensional crumpled paper-like MXene heterostructure（Pt/MXene）catalyst in this work.The HER performance of Pt/MXene was characterized by a systematic approach.In addition,the combination of spectroscopic characterization and density functional theory revealed the reasons for the excellent catalytic performance of Pt/MXene.The main research results of this dissertation are as follows:（1）The Pt/MXene catalyst was successfully prepared by a simple and efficient spray-drying method,which was continuous and reproducible.Using a series of characterization methods,it was confirmed that the three-dimensionalization of MXene nanosheets can effectively settle the problem of self-stacking,and the sub-nanometer Pt clusters are uniformly distributed on the 3D crumpled paper-like MXene.（2）By testing the electrocatalytic performance of the prepared Pt/MXene catalyst,the results show that the Pt/MXene catalyst designed by the heterostructure exhibits higher catalytic activity,such as low overpotential（34 m V）,high mass activity(1847 m A mg_Pt^-1),small Tafel slope(29.7 m V dec^-1),and high turnover frequency(10.66 H₂s^-1).（3）The high activity of the catalyst was analyzed by combining spectroscopy and density functional theory,indicating that the heterostructure can shift the density of states of the catalytic system towards the Fermi level.At the same time,the resulting"anchoring effect"can significantly induce the transfer of electrons on Pt to the MXene substrate.Based on the combined effect of the above factors,Pt/MXene exhibits higher catalytic activity and cycle stability.