Prussian Blue Analogues–derived Au Based Composite Catalysts For Sodium Borohydride Electrocatalytic Oxidation

BH₄^-electrocatalytic oxidation is the main anode reaction of direct borohydride fuel cell（DBFC）and also is one of the affect factors for DBFC performance.Precious metal Au catalyst can release 8e-in the process of BH₄^-electrocatalytic oxidation,and has high coulombic efficiency with little catalytic activity for BH₄^-hydrolysis.It is an ideal BH₄^-electrocatalytic oxidation catalyst,but its reaction kinetics process is slow,and its high price cannot be widely used,which restricts the commercial development of DBFC.In this thesis,different nitrogen-doped carbon-coated transition metal alloys and different Au loading form catalysts were prepared,and their electrocatalytic oxidation activitie for BH₄^-were studied.The main research contents are as follows:（1）NiFe@CN nanoparticles were obtained by annealing Ni₃[Fe（CN）₆]₂Prussian blue analogues.Au/Ni Fe@CN/C composite catalysts were obtained by using Ni Fe@CN/C nanoparticles as cocatalyst for Au catalyst.The morphology and structure of the prepared Au/Ni Fe@CN/C catalysts were characterized by TEM and XRD.It was found that Au nanoparticles and Ni Fe@CN nanoparticles were uniformly distributed on the surface of carbon supporter.The electrocatalytic oxidation activity of Au/Ni Fe@CN/C catalysts for BH₄^-were studied by electrochemical tests.It was found that Au_（50）Ni Fe@CN_（50）/C catalysts showed the best electrocatalytic activity,its peak current density for the electrocatalytic oxidation of BH₄^-could reach 50.9 m A cm^-2,and the electron transfer number could reach 7.3 close to the theoretical electron transfer number of Au catalyst.（2）CoFe@CN nanoparticles were obtained by annealing Co₃[Fe（CN）₆]₂Prussian blue analogues,and Au/Co Fe@CN/C composite catalysts were obtained by using Co Fe@CN/C nanoparticles as cocatalyst for Au catalyst.The morphology and structure of the prepared Au/Co Fe@CN/C catalysts were characterized by TEM and XRD.It was found that Au nanoparticles were supported on the surface of Co Fe@NC nanospheres.The electrocatalytic oxidation activity of Au/Co Fe@CN/C catalysts for BH₄^-were studied by electrochemical tests.Au_（50）Co Fe@CN_（50）/C catalyst showed the best electrocatalytic activity,and its peak current density for BH₄^-electrocatalytic oxidation could reach 48.8 m A cm^-2and electron transfer number could reach 6.4.In addition,Au/Co Fe@CN/C catalysts have obvious inhibitory effect for BH₄^-hydrolysis compared with Au/Ni Fe@CN catalysts.（3）FeMn@CN nanoparticles were obtained by annealing Mn₃[Fe（CN）₆]₂Prussian blue analogues,and Au/Fe Mn@CN/C composite catalysts were obtained by using Fe Mn@CN/C nanoparticles as cocatalyst for Au catalyst.The morphology and structure of the prepared Au/Fe Mn@CN/C catalysts were characterized by TEM and XRD.It was found that Au nanoparticles were completely coated on the surface of Fe Mn@CN nanospheres.Through electrochemical tests,it is found that although the catalytic activity of Fe and Mn is relatively low for BH₄^-electrocatalytic oxidation,but the special core-shell structure and synergistic effect of metals can obviously improve the electrocatalytic activity of the Au catalyst for BH₄^-electrocatalytic oxidation.