Process And Mechanism Of Rh Activation/breaking Of C-F Bond

Catalyzed/electroctalyzed reduction process plays an even increasing role in the safe and effective handle of a variety of environmental contaminates.It is generally believed that the catalyzed activation/cleavage of chemical bond with high stability,c.a.,carbon-halogen bond,nitro-oxygen bond,and halogen-oxygen bond is key and rate determine step during the decontamination reaction.Based on this understanding,Rh-based catalysts are considered to be the most ideal catalysts for reductive defluorination.Herein,through the hydrogen-deuterium（H₂-D₂）exchange experiment,we observed that the product hydrogen deuterium（HD,m/z=3）between H₂/D₂activation and recombination decreases rapidly on the surface of the Rh catalyst.Thus,it was confirmed that the excessive adsorption of H/D atoms on the surface of Rh leads to the decrease of the activation activity of H₂/D₂.The high binding energy of hydrogen atom（H）on Rh impedes its usage as reductant for reduction of carbon-fluorine bond（C-F）bond,moreover,the adsorbed H take up part of the reactive sites and unfavorable for the adsorption/activation of C-F bond,or these sites were poisoned by H/D.This dilemma can be facilely overcome by depositing Rh atom on the surface palladium nanowires（Pd NWs）.During the hydrodefluorination process,atomic H generated by Pd atoms continuous transfer to neighboring Rh atom,where the activated C-F bond is cleavage.By this way,the mass activity of Rh can be increased by more 50 times,and the activation energy of the hydrodefluorination process is also reduced from 46.2 k J mol^-1 to 25.8 k J mol^-1.Intriguingly,the deposited Rh atoms well retains the high activity of Rh nanocatalyst,which fast reduce the unsaturated primary hydrodefluorination product,c.a.,phenol,into cyclohexanol and cyclohexanone.The effectiveness of the proposed strategy is witnessed by depositing Rh on commercial Pd/Al₂O₃ catalyst to reduce flourited pollutants like hexafluorobenzene and perfluorooctane Acid at environment relevant conditions.Finally,we further obtained the structural information and catalytic activity of Pd and Rh by co-depositing Pd and Rh on the surface of gold nanowires（Au NWs）in the form of single atoms,and by correlating the surface Raman scattering spectra of the chemical adsorption probe molecules Relationship,systematically clarified the exact role of Pd and Rh from the atomic scale,thus deepening our understanding of the reaction mechanism.