Synthesis Of Platinum-Based Nanomaterials For Small Molecules Oxidation

To solve the two major problems of energy and environment during the development of human society,fuel cells known for being green,efficient and sustainable have always been the focus of attention in today’s society.Compared with hydrogen-oxygen fuel cells,direct small molecule（formic acid,methanol and ethanol）fuel cells have great advantages in energy density,safety,storage and transportation.However,current small molecule electro-oxidation catalysts have shortcomings such as low activity,poor stability and easy poisoning,which severely restricts their wide application.Therefore,it is imperative to develop highly efficient and anti-toxic electrocatalysts.In this article,around platinum-based nanomaterials,three strategies are used to improve the small molecule electrocatalytic activity:design the structure and morphology of materials and modify interface of materials.The main work are as follows:1.Hexagonal close-packed PtBinanoplates with triangular or truncated triangles were prepared via a wet chemical method.The edge size is 40～110 nm,and the thickness is about 11 nm.The synergistic effect of atomically ordered crystal structure and second-phase Bi atoms makes the PtBinanoplates have excellent catalytic performance and anti-toxicity during the oxidation of formic acid.In acidic electrolyte,the mass activity of FAOR at 0.85 V（vs RHE）is up to 0.55±0.02 A mg _Pt^-1,which is much higher than commercial Pt/C(0.037±0.004 A mg _Pt^-1).2.Using PtBi nanoplates as a template,PtBiM nanoplates modified transition metals are prepared by depositing transition metal M（Fe,Co and Ni）on the surface of the nanoplates.The addition of transition metals causes changes in the surface composition and electronic structure,which makes the catalysts show great differences in alcohol oxidation reactions.Under alkaline electrolyte,PtBiNi and PtBiCo have better methanol oxidation（MOR）and ethanol oxidation（EOR）performance,while PtBiFe is relatively poor.3.Based on PtBi nanoplates,through the principle of phase transition,2D intermetallicβ,γ-Pt Bi₂ nanoplates were successfully obtained.β-Pt Bi₂andγ-Pt Bi₂nanoplates have cubic and trigonal crystal phase structures,respectively.The shapes are pseudo-circular,the diameter is within 50 nm,the thickness is within 10 nm,and the surface is rich in grain boundaries and nano-grooves.Ordered atomic arrangement and wider atomic spacing make intermetallicβ,γ-Pt Bi₂ nanoplates exhibit excellent small molecule electro-oxidation properties.In 0.1 M HCl O₄,the FAOR mass activities ofβ-Pt Bi₂ andγ-Pt Bi₂ nanoplates at 0.85 V（vs RHE）are 1.1±0.01 A mg _Pt^-1 and 0.85±0.01A mg _Pt^-1,respectively,which are approximately commercial 30 times and 23 times of Pt/C.Meanwhile,the mass activities still retained 86.8% and 92.9%of the initial activity after the chronoamperometry test for 1 h,which is far better than the 79%of commercial Pt/C.In 1 M KOH,mass activities of β-PtBi₂ andγ-Pt Bi₂ nanoplates were8.69±0.17 A mg _Pt^-1and 7.36±0.15 A mg _Pt^-1 for MOR,8.21±0.4 A mg _Pt^-1 and 6.63±0.26 A mg _Pt^-1 for EOR,and there is basically no decrease in activity after the stability test,which is one of the best AOR catalysts reported in alkaline electrolyte.CO-stripping in acid and alkaline electrolyte confirmed that the excellent catalytic activity of intermetallicβ,γ-Pt Bi₂ nanoplates comes from good anti-toxic properties.