Electronic Structure Regulation And Electrocatalytic Performance Of Pt And Pd Based Nanomaterials

Noble-metal-based nanomaterials are widely used in electrocatalysis,however,the scarcity of noble metal reserves itself,the easy agglomeration and deactivation of nanoparticles,and the easy poisoning during the catalytic process make the large-scale application of noble-metal-based catalysts seriously limited.It has been shown that the tuning of d-band center position and d-p orbital hybridization can greatly affect the catalytic activity of noble-metal-based nanomaterials.This thesis focuses on the electronic structure modulation of Pt and Pd based catalysts to examine their effects on electrocatalytic performance,as shown below.1.This section investigates the role of surface strain in ternary alloy Pt-Cu-Mn nanoframes(NFs)on their d-band centers and the modulation of oxygen reduction(ORR)reaction activity.The Pt-Cu-Mn ultrafine nanoframes(UNFs)exhibit a compressive strain of about 1.5% compared to the Pt-Cu-Mn penta-twinned ternary nanoframes(PNFs),resulting in a shift of the d-band center of the Pt-Cu-Mn UNFs in the negative direction by about 0.28 e V compared to that of the Pt-Cu-Mn PNFs.the Pt-Cu-Mn UNFs with compressive strain exhibit a higher strain in the alkaline environment than the Pt-Cu-Mn PNFs.exhibited higher ORR activity than Pt-Cu-Mn PNFs with 1.45 and 1.71 times higher specific and mass activities than Pt-Cu-Mn PNFs,respectively,and 8.67 and 9.67 times higher compared to commercial Pt/C,indicating that the compressive strain in the nanobox structure could effectively enhance the catalytic activity of ORR.Theoretical calculations show that the compression on the surface of Pt-Cu-Mn UNFs causes the d-band center to move away from the Fermi energy level,weakening the adsorption strength of oxygen-containing intermediates and thus creating favorable conditions for ORR(see Chapter 2 section of this thesis for details).2.In this chapter,Pd-Pd Se heterostructural nanosheets(HNSs)were prepared in one step,and Pd-Pd Se HNSs have unique p-d orbital hybridization and approximately 3.5% tensile strain compared to pure Pd nanosheets(NSs).Compared with commercial Pd/C and Pd NSs catalysts,Pd-Pd Se HNSs have 5.5 and 2.5 fold higher specific activity and 6.6 and 2.6 fold higher mass activity for ethylene glycol electrooxidation reaction(EGOR).In particular,the Pd-Pd Se HNSs also exhibited excellent C-C bond cleavage ability,with a C1 path selectivity of up to 44.3%.Combined with electrochemical in situ FTIR spectroscopy and DFT calculations,both the p-d orbital hybridization and the 3.5% stretching strain effect possessed by Pd-Pd Se HNSs can reduce the activation energy of C-C bond cleavage while accelerating CO* oxidation,which is highly advantageous in promoting the complete oxidation of ethylene glycol and improving the catalytic performance of the catalyst(see Chapter 3 section of this thesis for details).