Controllable Preparation Of Palladium/Mo-Based Catalysts And Their Electrocatalytic Properties

In this paper,ammonium molybdate was used as the molybdenum source and the modification of samples was carried out by doping different metal atoms.Two types of Mo₂C matrix composites doping with different metal atoms were designed and prepared.Their electrocatalytic performances for ethanol were evaluated after loading Pd.The correlation between the morphology and catalytic performance of the samples was discussed.The research results are as follows:1.The Mo-based precursors containing Fe,Ni and Co were prepared by blending crystallization method.The precursors were first oxidized by air at 600°C for the preliminary pore modification through the escape of volatile components.Then MoO₃doped with different metals was obtained.The pore structure is further optimized by controlled alkali treatment.The M-Mo₂C-（T）（M=Fe,Ni,Co,T means alkali treatment operation）carrier was obtained underwent the gas-solid reaction at 900℃.Finally,Pd was loaded onto the carrier by metal substitution reaction.The obtained catalyst was named Pd/M-Mo₂C-T.The experimental results showed that the Pd/Ni-Mo₂C-T nanoparticles exhibited the best dispersibility,uniform particle size distribution and rough surface,and the supported Pd metal particles are uniformly dispersed on the surface of Mo₂C particles.Since the loading of palladium was through ametal replacement reaction,it showed a stronger binding force with the carrier Mo₂C.The residual Ni atoms could produce a good synergistic catalytic effect with Mo₂C and Pd.The electrocatalytic performance of Pd/M-Mo₂C-（T）catalysts for ethanol oxidation was studied by electrochemical method.The results showed that all the samples showed a certain electrocatalytic property for ethanol oxidation.Among them,Pd/Ni-Mo₂C-T catalyst（containing 10 wt%Pd）exhibited the best catalytic performance for ethanol oxidation.Its mass activity reached 2283.2 mA/mgPd,which was 2.6 times that of 10 wt%commercial Pd/C catalyst.This was mainly due to the smaller particles,uniform particle size distribution,higher specific surface area and the stronger binding force and synergy effect between Mo₂C and Pd.2.Ammonium molybdate and nitrate of cobalt and nickel were used as raw materials,dissolved in deionized water with a certain amount of Mo/Co/Ni mass ratio nanocomposite precursor was obtained by self-assembled method.The volatile components and moisture were removed by oxidized at 600°C.The CoNi-Mo₂C carrier with many uniformly dispersed nanotubes（CNT）was obtained by a high temperature carbonization reaction.The two utilized metals in composite material played different roles in the high-temperature reduction preparation process.The presence of Ni inhibited the aggregation of Mo₂C particles,resulting in a more uniform particles size distribution,whilst Co catalyzed the in situ formation of CNTs as a growth site to increase its dispersion and exposure of surface active sites.And the Pd/CoNi-Mo₂C catalyst was prepared by replacement reaction of Ni and Co components.The effects of different preparation conditions such as metal doping ratio,precursor treatment and carbonization temperature on the morphology and catalytic properties of the catalyst were investigated.The preparation conditions were further optimized.When the ratio of Mo/Co/Ni precursor was 5:1.5:1.5 and carburized at800°C for 2 h,the bimetallic doped Mo₂C catalyst presented a better morphology and electrochemical performance after loading palladium.The ethanol oxidation current density and residual current of catalyst（containing 10 wt%Pd）was 3351.6 mA/mPd and 501.4 mA/mgPd,respectively,which clearly overtook those of 10 wt%commercial Pd/C catalyst.The preparation method used in this experiment is simple,the raw materials are cheap and easy to obtain,and the electrocatalytic oxidation of ethanol has achieved good results,or can be extended to the related preparation of the same type of catalyst.In this experiment,a simple preparation method and the conventional raw materials were used to prepare palladium/Mo-based catalyst and the prepared catalyst showed a good electrocatalytic performance for ethanol oxidation.It may be extended to be applied in related preparation of similar catalysts.