Density Functional Theory Study On Catalytic Performance Of Platinum-based Binary Cluster For Methanol Oxidation

It is well known that pure platinum has been the most effective anode catalyst for direct methanol fuel cells because of its high catalytic activity.But pure platinum,as an anode catalyst,also has two fatal shortcomings,which restrict the commercial application of methanol fuel cells.First,because the metal platinum is a kind of precious metal,the storage of the earth is limited,which leads to the high cost of the pure platinum catalyst.Second,the decomposition of methanol catalyzed by pure platinum will form carbon monoxide,which is easily adsorbed on pure platinum catalyst to cause poisoning and lead to inefficiency of catalyst.Therefore,looking for an efficient,inexpensive catalyst that can replace pure platinum is the most important thing in the commercial application of direct methanol fuel cells.In this paper,we use the density functional theory?DFT?mainly studies the methanol reaction on the PtCu cluster and FePt cluster with two different reaction path,?1?direct dehydrogenation of methanol,the reaction path of carbon monoxide;?2?the reaction path of methanol decomposition with the assist of hydroxyl to formic acid and continuous decomposition.And the most stable structure in the reaction,the adsorption energy of methanol on the cluster,the energy barrier needed for every step reaction,the potential energy surface of reaction and the electron transfer between methanol and clusters are discussed.The main results are as follows:through the calculation of the potential energy surface showed that for PtCu cluster,Pt₇,Pt₃Cu₄ and Cu₇ three clusters can catalyze the oxidation of methanol.Each cluster has its own advantages and reaction trends.The most suitable reaction path for Pt₇ cluster is direct dehydrogenation of methanol to generate carbon monoxide,and the energy barrier needed to react is lower than that of the other two clusters.However,the generated carbon monoxide can cause the catalyst to be poisoned.For Cu₇ clusters,methanol is not easy to direct decomposition,and is more inclined to dehydrogenate to produce carbon dioxide.On the Pt₃Cu₄ cluster,the energy required for dehydrogenation of methanol is lower than that of the Cu₇ cluster,and is also inclined to produce the final product of carbon dioxide.For FePt clusters,on the three clusters of Fe₇,Fe₃Pt₄ and Pt₇,every step reaction of methanol dehydrogenation is low,and methanol can directly decompose and degenerate hydrogen to form carbon monoxide.As a whole,the energy required for the decomposition of methanol on the Pt₇ cluster is the lowest.For the reaction path of hydroxyl participating in oxidation,Fe₇ cluster catalyzes the formation of formic acid and formic acid dehydrogenation is too high.The reaction is difficult to happen,this indicates that the reaction path is not competitive on Fe₇ cluster.But on the other two clusters,although the reaction can happen according to the reaction barrier,it can have a higher barrier compared with the direct decomposition of methanol.It is at a disadvantage in the competition of the two reaction paths,which is more suitable for the reaction of direct decomposition of methanol.The above research results,proved that the Pt Cu cluster and FePt cluster of methanol decomposition and oxidation have good catalytic properties.Our research provides a theoretical basis for the experimental study on the catalytic properties of PtCu cluster and FePt cluster catalyst,and provides a reference value for the design of more efficient and practical anodic catalysts for methanol fuel cells.