Study On The Role And Regulation Mechanism Of Defects In Electrocatalytic Reaction Process

In recent years,energy crisis and environmental pollution have become two major problems for human beings.Electrocatalytic process can efficiently remove pollutants and convert chemical energy into electrical energy,which is a powerful means to deal with the above problems.As a special class of defects,such as twin boundary,stack fault and lattice defect,noble metal nanocrystals may have unique activities and functions in the catalytic processes of environment and energy.In this study,Pd and Pt superfine nanowires with abundant surface defect sites were used as model catalysts to systematically study the role of defect sites in the processes of electrocatalytic indirect reduction dehalogenation and electrocatalytic methanol oxidation,which have important environmental/energy significance.First,we studied the distribution of adsorption activity H(H*ads)on Pd nano-catalysts with different structures and the electrochemical reduction dehalogenation activity by controlling the relative abundance of surface defects of the catalysts.Thanks to a large number of defects on its surface,superfine polycrystalline Pd nanowires(NWs)can consume more than 40%of the electrons to convert into H*ads during the electrochemical reduction process.Under this influence,the normalized rate constant of the electrocatalytic reduction and dehalogenation is as high as 13.8±0.8h-1·m2,which is 8-9 and 15 times higher than that of ordinary Pd/C catalyst and defectless Pd/C catalyst,respectively.The central role of defect sites was further confirmed by Rh and Pt atom sealing experiments,and theoretical calculation also confirmed that the adsorption energy of H*ads at defect sites was much higher than that on the crystal surface of Pd{111}.At the same time,we found that the defect sites are the main toxicosis point of Pt for catalytic oxidation of methanol and ethanol,and selective deposition of Rh atoms on the defect sites can effectively inhibit poisoning product to reduce the overpotential of reaction process,promote the complete oxidation of methanol and ethanol to generate CO2,and significantly improve the catalytic activity and stability.The results of this study suggest and confirm that defect sites play an important role in the electrocatalytic process,and the development of strategies to selectively block the sites is expected to provide new ideas for the design of electrocatalysts in the later stage.