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Computational Study Of Oxygen Evolution Reaction Catalyzed By Binary Monolayered Double Hydroxides

Posted on:2020-10-30Degree:MasterType:Thesis
Country:ChinaCandidate:J L MaFull Text:PDF
GTID:2381330602460758Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
In recent years,layered double hydroxides(LDH)have been widely studied as a two-dimensional material catalyst because of their tunable denaturation,high active site dispersion,and interlayer anion exchangeability.A large number of experimental reports indicate that monolayered double hydroxides that has been stripped out and has better oxygen evolution reaction(OER)activity.In this thesis,the experimental results are selected to obtain the best hydrotalcite(NiFe-LDH)in the catalytic OER.The mechanism of OER on the three faces((001),(110)and(100))of two ratios(Ni2Fe-Cl-LDH,Ni3Fe-Cl-LDH)were systematically studied,and the active sites of Ni and Fe of synergism in the reaction were clarified in detail.Based on the results,the photocatalytic and electrocatalytic properties of five binary monolayer hydrotalcites were discussed.The specific research content of this thesis and the conclusions obtained are as follows:(1)DFT method was employed for calculating OER mechanism on the O site on(001)face,the Ni,Fe,O sites on(110)face,Ni-Ni and Ni-Fe bridge sites on(100)face in Ni2Fe-Cl-LDH.The results show that the Ni site on the(110)face has the smallest overpotential and the best OER activity.The analysis of the electronic properties of LDHs shows that Ni2Fe-Cl-LDH is visible light absorption;Ni2Fe-Cl-LDH cannot overcome the overpotential of OER by its own driving force,and an external voltage is required to make the reaction proceed.(2)Select 3:1 NiFe LDH(Ni3Fe-Cl-LDH)as catalyst,six sites(the same as Ni2Fe-Cl-LDH)as active sits,to inverstgate the overpotentials.The results show that the Ni-Fe bridge site of the(100)face has the best OER activity;Ni3Fe-Cl-LDH is visible light absorption,and there is no strong photo-cavitation ability;Ni3Fe-Cl-LDH cannot overcome the overpotential by driving force to generate an OER,and an external voltage is required to promote the reaction.(3)According to the above results,the active site,which has the lowest overpotential(Ni,Fe bridge site of(100)faces in the Ni3Fe-Cl-LDH),is selected for metal modulation.The divalent metal is changed to Co,and the high-valence metal is changed to Cr,Mn,and Al.The OER catalytic mechanisms of Ni3Cr-Cl-LDH,Ni3Al-Cl-LDH,Co3Mn-Cl-LDH,Co3Fe-Cl-LDH show that the OER activity of Co3Fe-Cl-LDH is the best one(the minimum overpotential).The photocatalytic and electrocatalytic properties of five LDHs including Ni3Fe-Cl-LDH were analyzed.As the number of d electrons in the metal increases,the band gap decreases and photocatalytic OER is more likely to occur.;The overpotential and driving force of the five of LDHs are compared respectively.The results show that Ni3Cr-Cl-LDH can process photocatalytic OER;Ni3Fe-Cl-LDH has the best electrocatalytic OER activity,mainly because it has the smallest overpotential,which is beneficial to the reaction.Ni3Fe-Cl-LDH has the smallest band gap,which is beneficial to electron transfer.Fe helps to receive electrons from water.
Keywords/Search Tags:monolayered double hydroxides, oxygen evolution reaction, overpotential, reaction mechanism
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