The Surface Engineering Of Pt-Mn/Pt-Mo Catalysts And Their Electrocatalytic Performance

The catalysis of noble metal nanomaterials is typical surface and interface-sensitive.Effective surface control over nanomaterials provides important foundation for studies of structure-dependent catalysis,which is critical to the design of nanocatalysts with optimized catalytic performances for practical applications.Today,catalysts of fuel cells and hydrogen-producing from water electrolysis are Pt/C,but their activity and stability are always poor.Therefore,rational design of the surface structure of Pt-based catalysts is crucial to improve the activity and stability of catalysts.A large number of studies have shown that the nanostructures with specific morphology,crystalline phase and composition are the limiting factors for the catalytic performance.As we know,Pt-based nanocrystals catalysts are susceptible to corrosion under electrolytes and high potentials during the reaction process,which will cause the performance loss of catalysts.Especially,Pt-based nanocrystals with high-indexed facets(HIFs)are also thermodynamically unstable and can easily cause surface restructure and rearrangement in electrolytes because of the highly active unsaturated atoms and the high surface energy.So,a strategy to advance the fundamental surface study on Pt-based HIFs materials is addressed by implanting foreign component as“active auxiliary”into the near-surface of noble metal nanocrystals bounded with HIFs to engineer a stable structured catalyst.Therefore,seen from the viewpoints of surface structure and composition,the research content of this paper includes three following aspects:1.Oxophillic Mo was used as the“active auxiliary”to modify the Pt₃Mn nanocrystals with HIFs.The electronic structure of the surface Pt atom was modified by Mo surface implantion,thus improving the electrocatalytic performance of Pt.In the process of electrocatalytic reaction of ethylene glycol,the addition of Mo can change the oxidation pathway of ethylene glycol:Mo/Pt₃Mn surface is not only conducive to the bond-breaking of C-C of ethylene glycol,but also promoting to the direct oxidation of C1 intermediate into CO₂,without the formation of CO.The stability test shows that the addition of Mo is conducive to stabilizing the surface Mn atoms,making it difficult to be dissolved during the reaction process,enhancing the structure stability of the catalyst,and thus improving the catalytic activity and stability of catalysts.2.On the basis of the above work,we found that the addition of Mo was beneficial to stabilize the structure of catalyst,and enhancing the catalytic performance(activity and stability).Herein,Ru component serving as“active auxiliary”was selected and the Ru modified Pt₃Mn nanocrystas with HIFs were also constructed to explore the promoting effect towards electro-oxidation reaction of ethylene glycol.The isolated Ru atoms and Ru nanoparticles were introduced onto surface of Pt₃Mn concave nanocubes.On the basis of the electrochemical in situ Fourier transform infrared spectroscopy results,the Pt₃Mn catalysts modified by isolated Ru atoms promote not only the C-C cleavage of EG,but also the rapid oxidation/removal of intermediate CO_ads.The density functional theory calculations demonstrated that Pt₃Mn catalysts modified by isolated Ru atoms possessed a lower reaction barrier for oxidation of CO_ads assisted by adsorbed OH_ads,and an energy-favorable position for reaction between CO_ads and OH_ads.3.In this section,we introduced S as“active auxiliary”onto the surface of Pt₈₅Mo₁₅ nanowires to engineer a novel-structured catalyst with high activity and durability.We fabricated an ultralong jagged Pt₈₅Mo₁₅-S nanowires with rich“interfacial active sites”to demonstrate the enhanced catalytic HER performance.The Pt₈₅Mo₁₅-S nanowires exhibit exceptional activity with 3.62 times specific current density and 4.03 times mass current density higher than commercial Pt/C,as well as excellent stability towards alkaline HER.The X-ray photoelectron spectroscopy reveals that S element could obviously maintain the electron density of Pt via preventing the further oxidization of Mo.In addition,the theoretical calculations demonstrate that the water dissociation energy barrier can be significantly reduced under the interfacial synergy of intimate contact between Pt and Mo S_x.