Theoretical Study Of Water Gas Shift Reaction On Ni Group And Cu Group Metals

It is need to devolop a renewable energy due to solve the energy crisis.In recent years,hydrogen energy has acctracted the researcher's attention due to high caloric value,environment friendly and renewable sources.Hydrogen is also an important chemical material.Nowdays,the hydrogen mainly comefrom steam reforming of nature gas and coal gasification.However,the reformed gases contains amount of CO,which may degrade the performance of the catalyst.The water-gas shift?WGS?reaction can improve the purity of H₂ and decrease the content of CO in the gas,then the gas can be directly used.With the development of fuel cell,the scientists has paied more and more attention to the reaction,because the traditional WGS catalyst has lowat the low temperature.Therefore,it is essential to develop a new type kind ofWGS catalyst.In this paper,we use the VASP software to study the WGS reaction mechanism on six different metal surfaces by density functional theory.The reaction energy,activation energy and the corresponding transition state of the elementary reaction are also discussed.The conclusions of the paper are as follows:?1?The reaction mechanism of WGS reaction is the same on the Ni?111?,Pd?111?,Pt?111?and Cu?111?,which is as follows:CO+2H₂O?CO+2OH+2H?CO+H₂O+O+2H?CO₂+H₂O+H₂?redox pathway?.?2?On Ag?111?and Au?111?surfaces,the mechanism of WGS reaction is different from the above-mentioned metals,and the optimal path on both surfaces is carboxylic acid intermediate path?CO+2H₂O?CO+2OH+2H?COOH+OH+2H?CO₂+H₂O+H₂?.?3?On the Pd?111?,Pt?111?,Cu?111?,Ag?111?and Au?111?surfaces,the ratedetermining step of the WGS reaction are the water decomposition,and corresponding energy barriers are 0.95,1.00,1.30,2.06,and 2.02 eV,respectively.Theratedetermining step on Ni?111?surface is CO₂ formation.In summary,the Pd?111?surface is the most favorable catalyst for the WGS reaction.