Study On Modified AB₅-type Hydrogen Storage Alloy As Anode Catalyst For Direct Borohydride Fuel Cell

Direct borohydride fuel cell(DBFC)is an alkaline fuel cell that directly converts the chemical energy stored in the cell into electrical energy.This type of battery has attracted much attention due to its high theoretical voltage,high energy density,high conversion efficiency,and environmental protection without pollution.The performance of DBFC is directly controlled by its anode catalyst.However,the conversion efficiency of the battery is not high due to hydrolysis of the anode catalyst.In addition,in the past,noble metal elements or alloys were mostly used as anode catalysts,and the cost also greatly restricted their wide application.Therefore,it is urgent to find a cheap,high-catalytic anode catalystHydrogen storage alloy with unique hydrogen storage function can store hydrogen and also release hydrogen under certain conditions.If a hydrogen storage alloy is used as the anode catalyst of DBFC,the two fatal shortcomings of high cost and easy hydrolysis of the previous anode catalyst can be abandoned,so this proposal has received great attention.Based on the stable performance of the AB5 hydrogen storage alloy,the structure,electrochemical performance and catalytic performance as anode catalyst for DBFC of the modified AB5-type alloy were studied,and the relationship between structure,electrochemical performance and catalytic performance was analyzed in this paper.Some important research results are as followsFirstly,in the study of the influence of ball milling time on the structure,electrochemical performance and catalytic performance of AB5 hydrogen storage alloy as anode catalyst for DBFC,it was found that ball milling did not change the phase composition of the alloy,but changed the phase structure of the alloy.All ball-milled AB5-type alloys consist of a single CaCu5-type LaNi5 phase.With the increase of ball milling time,the degree of amorphization of the alloy becomes more and more serious,the maximum discharge capacity,discharge performance and cycle stability of AB5-type alloy gradually deteriorated,and the catalytic performance and stability of ball milled AB5 alloy as anode catalyst for DBFC also gradually deteriorated.It can be seen that the electrochemical performance of ball-milled AB5 alloy has a positive correlation with its catalytic performance as a DBFC anode catalyst.The as-cast MmNi3.55Co0.75Mn0.4Al0.3(Mm is Ce-rich rare earth)hydrogen storage alloy exhibits the best comprehensive electrochemical performance and catalytic performance as anode catalyst for DBFCSecondly,CNTs/AB5 composite hydrogen storage alloys were prepared by ball milling AB5-type MmNi3.55Co0.75Mn0.4Al0.3 alloys and carbon nanotubes(CNTs)in different ball milling times.The electrochemical performance and the catalytic performance as anode catalyst for DBFC of CNTs/ABs composite alloy were studied.The results show that the CNTs composite does not change the phase structure of AB5-type alloy.With the increase of ball milling time,the electrochemical performance and its catalytic performance for BH4-of CNTs/ABs composite alloy both increase first and then decrease.It can be predicted that the electrochemical performance of the composite alloy is positively correlated with the catalytic performance as anode catalyst for DBFC.The CNTs/ABs alloy with ball milling for 2 h shows the best electrochemical and catalytic propertiesFinally,in consideration of the excellent electrical and catalytic properties of the precious metal silver(Ag),different contents of Ag/ABs composite hydrogen storage alloys were prepared by ball milling.The structure,electrochemical properties and the catalytic performance for the BH4-of Ag/AB5 composite hydrogen storage alloys were studied.The results show that the Ag/AB5 composite hydrogen storage alloy is still composed of a single CaCus-type LaNis phase.With the increase of Ag content,the electrochemical performance and catalytic performance of Ag/AB5 composite hydrogen storage alloy both increase and then decrease.When the Ag content is 2 wt.%,The Ag/ABs composite alloy has good electrochemical performance and catalytic performance for BH4-.