Preparation And Electrocatalytic Properties Of Nanoporous Pd-Bi Intermetallic Compounds

Nanoporous metal material are materials,that composed of continuous metal ligaments and nano-sized pores.Because of its advantages of low density,high specific surface area,electrical conductivity and thermal conductivity,it has wide applications in electrocatalysis,filtration and separation,heat exchange,sensors and actuators,etc.Intermetallic compounds have shown high efficiency and high selectivity in catalysis research due to their ordered atomic arrangement and atomic cooperation.They are a class of efficient catalytic materials attracting much attention.Based on the characteristics of metal atoms,integrating the component design,porous structure preparation and catalytic performance of intermetallic compounds is the key to the development of novel nanoporous catalysts.Thus,based on the chemical,electrochemical and catalytic properties of Pd and Bi metals,nanoporous Pd-Bi intermetallic compounds including Pd Bi₂,Pd₈Bi₃ and Pd₃Bi were prepared by metal melting and selective corrosion.Their electrocatalytic properties toward nitrogen reduction reaction and formic acid oxidation reaction were studied,as well as related reaction mechanism.The main research contents and results are summarized as following:1.According to the phase diagram,a series of Pd-Bi parent alloys were designed,and the selective corrosion method of active phases were explored.Nanoporous Pd Bi₂and Pd₈Bi₃ have been obtained by controlling the corrosion time and temperature to adjust the components,pores and morphology.Nanoporous Pd Bi₂ exhibits good catalytic ability for electrochemical nitrogen reduction.In 0.05 M H₂SO₄,the NH₃ yield under-0.2 V vs.RHE is 6.50?g h^-1mg^-1_cat,and the Faraday efficiency is 18.56%While nanoporous Pd₈Bi₃ shows a good catalytic ability for formic acid oxidation.The highest catalytic response is 1.17 m A cm^-2_ECSA at 0.6 V vs.RHE,which is 2.1 and 2.6 times that of nanoporous Pd Bi₂ and commercial Pd/C,respectively.These results show that Pd-Bi-infer compounds can show the catalytic advantages of Pd and Bi with atomic synergy,improving NRR activity with inhibited hydrogen evolution reaction and improving oxidation of formic with reducing CO toxicity.2.Based on the above exploration,the electrochemical dynamic corrosion method is involved for further phase transition of Pd Bi₂ to obtain nanoporous Pd₃Bi.The nanoporous Pd₃Bi has exhibited high efficiency,high selectivity,and high stability toward electrocatalytic nitrogen reduction.In 0.05 M H₂SO₄,the NH₃ yield of the nanoporous Pd₃Bi at-0.2 V vs.RHE is 59.05±2.27?g h^-1mg^-1_cat,and the Faraday efficiency is(21.52±0.71)%,which is better than most prerious reports.In-situ/Operando X-ray absorption fine structure spectroscopy and Density Functional Theory(DFT)calculations show that(1)the strong coupling between Pd-Bi sites bridging the electron transmission channel in the intermetallic compound;(2)during the nitrogen reduction process,Bi sites have a strong interaction with N₂ molecules to promote the adsorption and activation of N₂,while Pd sites mainly adsorb H^*intermediates,and the interaction contributes to the reduced energy barrier of the nitrogen reduction.Also,the bi-continuous nanoporous structure accelerates the mass-charge transfer in the nitrogen reduction process,thereby further improving the nitrogen reduction performance.