Effect Of Rare Earth Oxides And Hydroxides On The Catalytic Electrooxidation Properties Of Nanocatalytic Materials

Nowadays,people are paying more and more attention to energy shortage and environmental pollution.Developing green and clean energy materials has become an important research topic.The electrooxidation of alcohol and water is two important types of electrooxidation in the field of energy electrocatalysis.The alcohol electrooxidation reaction mainly occurs on the anode of a direct alcohol fuel cell?DAFC?,which is currently commercialized as a noble metal Pt catalyst.However,Pt is easily poisoned by the oxidation intermediates such as CO during the electrocatalytic oxidation of the alcohol,resulting in a decrease in catalyst performance.At the same time,the high price of Pt has greatly limited the commercialization of alcohol fuel cells.In addition,the hydroelectric oxidation reaction is a half-cell reaction for electrolysis of water to produce hydrogen.As a non-precious metal catalyst,NiFe layered bimetallic hydroxide?NiFe LDH?is low cost and it has large specific surface area.But it is susceptible to corrosion and loss of activity in an acid or alkaline solution.In this paper,aiming at the development of low-cost,high-catalytic alcohol electrooxidation catalysts and high-stability NiFe-based water oxidation catalysts,we investigated the enhancement of Pt-based alcohol electrooxidation catalysts with rare earth?Pr,Ce?oxides and hydroxides.We also investigated the role of ceria for NiFe LDH on the stabilization.The main research contents and conclusions are as follows:?1?Short rod-shaped Pr?OH?₃ nanoparticles were prepared by t-butylamine-assisted solvothermal method and calcined at 500? to obtain oxide Pr₆O₁₁.Characterization shows that the surface of Pr?OH?₃ is rich in-OH,which contains almost no oxygen vacancies,while Pr₆O₁₁1 contains more oxygen vacancies.Pr?OH?₃ or Pr₆O₁₁1 were mixing with platinum/carbon nanotubes?Pt/CNT?respectively by ultrasonic which can improve the catalytic performance of methanol electrooxidation by 1.61 times and 1.87 times that of Pt/CNT,respectively.The samples calcined at different temperatures was ultrasonically mixed with Pt/CNT,and Pt/CNT-Pr₆O₁₁?100??had the best catalytic activity because it was rich in both-OH and oxygen vacancies.?2?Small-sized and uniformly dispersed nanoparticles such as Pr_xCe_y?OH?_a and CeO₂·H₂O were prepared by t-butylamine-assisted solvothermal method,and their oxides were obtained by calcination.The as-prepared nanoparticles were simply ultrasonically mixed with Pt/CNT and commercial Pt/C.The oxides obtained by Pr_xCe_y?OH?_a and its calcination have different degrees of catalytic properties for Pt/CNT and commercial Pt/C.The catalytic activity of Pt/C-Pr₁Ce₆?OH?a is 2.97times that of commercial Pt/C.The stability is also greatly improved,and the current value retention ratio is 72%.The yttrium and lanthanum doped CeO₂·H₂O can also significantly promote the catalytic performance of commercial Pt/C for methanol.?3?NiFe layered double hydroxide was grown on oxidized carbon nanotubes?OCNT?under alkaline conditions,and the synthesis conditions were adjusted to prepare NiFe LDH/OCNT with the lowest overpotential.The overpotential was 320 mV.Subsequently,CeO₂ was precipitated outside NiFe LDH/OCNT to prepare a CeO₂-coated NiFe LDH/OCNT catalyst.The results show that CeO₂ coating can significantly improve the stability of NiFe LDH/OCNT,but the activity is not as good as NiFe LDH/OCNT.This may be because the NiFe active sites are covered by CeO₂although they are not easily corroded after CeO₂ coating.So the activity is slightly worse.