Study On The Defect-Induced Charge Regulation For Electrocatalyst

Increas ing e nergy de mand has led to rapid cons umptio n of trad itio na l foss il fue ls,and the conseque nt e nergy cr is is and enviro nme nta l issues dr ive peop le to regulate the c urre nt ener gy str ucture and exp lore new ener gy storage a nd convers io n techno lo gies.Electroche mica l e nergy storage and convers io n devices,such as fue l cells,meta l-air batter ies,a nd electroc he mica l water deco mpositio n,have attracted great atte ntion.For these electroc he mica l ener gy devices,the electroc he mica l reactio n occur at the working e lectrode o f the device d irectly deter mines the energy-convers io n e ffic ie ncy.Electrocata lysts ca n e ffective ly reduce the reactio n overpotentia l,a nd thus impro ve ener gy-convers ion e ffic ie nc y of these devices.Traditiona lly,prec ious meta ls suc h as platinum,rhod ium and r uthenium,have been regarded as the best catalysts for e lectrocata lytic react ions.Howe ver,the ir scarce abundance,high cost and poor stab ility severe ly ha mper the lar ge-sca le applicatio n.There fore,the deve lop ment of ine xpens ive no n-precious meta l cata lysts and the enha nce me nt o f the cata lytic per for ma nce of prec ious meta l cata lys ts are of great significa nce for the commerc ia l app licatio n of e lectroc he mica l ener gy storage and conversion technologies.The e lectrocatalytic reaction occurs at the inter face of e lectrode and the electro lyte.The process of the e lectroc he mica l reactio n ma inly invo lves the tra ns fer of matter a nd the tra ns fer o f e lectrons.The e lectrode inter face a nd the e lectro nic structure of the e lectrocatalyst d irectly a ffect the cata lytic perfor ma nce of the electrocata lyst.How to des ign high-perfor ma nce e lectrocatalysts?We s hould first clar ify that what is the active s ite o f the e lectroche mica l reaction and how to increase the number of active site.In this regard,this thes is aims to analyze the relatio ns hip between sur face charge a nd electroc he mica l reaction per fo r mance based on defects.I n order to clar ify the influe nce of s ur face char ge on the cata lytic perfor mance,high-oriented pyro lytic grap hite?HOPG?was used as the mode l electrode,regula ting the sur face char ge of HOPG thro ugh sur face de fect engineer ing,and fina lly demons trates the relatio ns hip between defect-charge-catalytic perfor mances.Based on the understand ing of the rela tions hip between the electrocata lytic perfor ma nce and the c harge o f na no mater ia ls,firstly,MOFs are etched by p las ma to for m meta l unsaturated s ites,the char ge o f the cata lytic meta l site is regulated,thus enha nce the cata lytic per for ma nce.Secondly,a iming at the character istics of methano l e lectro-oxidatio n poisoning of noble meta l platinum-based electrocatalysts,the defect cerium oxide is used to change the char ge dens ity of p latinum na nopartic les,and the anti-toxic ity o f p latinum-based mater ia ls is impro ved,thereby impro ving the cata lytic per for mance o f the catalyst.The detailed researches are described below:?1?Electrocata lys is is dominated by reaction at the solid–liq uid-gas inter face,and the sur face properties o f electrocata lysts deter mine the e lectroche mica l beha vior.The s ur face char ge of active s ites on cata lysts can s ignifica ntly modulate the adsorption and desorption of inter med iates and tune the e lectrocatalys is.However,there is no d irect evide nce to br idge the sur face char ge and cata lytic activity o f active s ites.I n this work,we contro llab ly created defects?active s ites?on HOPG?highly or iented pyrolytic grap hite?s ur face and broke the intr ins ic sp²-hybr id izatio n of graphite by p las ma,whic h ind uces the localiza tion o f s ur face c harge o nto defective active s ites,as proved by scanning io n conducta nce microscopy?SICM?and Kelvin probe force microscopy?KPFM?.The e lectroche mica l test revea led the significa ntly enha nced intr ins ic activity by the loca lized sur face char ge.The DFT calc ulation confir med the re latio ns hip between s ur face char ge and cata lytic activity.This work directly corre lates sur face charge and c ata lytic activity,which provides the ins ight into the e lectrocatalytic beha vior and would guide the design of advanced electrocatalysts for various reactions.?2?Metal-orga nic-fra meworks?MOFs?,in whic h me ta l io ns are single-atomica lly d ispersed,are regarded as one of the most promis ing s ingle-atom doped catalysts.Co-based species ha ve been co ns idered as a potentia l cand idate to replace the precious RuO₂ to electrocata lyze oxyge n evo lutio n reaction?OER?.Zeolitic imida zola te fra meworks-67?ZIF-67?,a Co-conta ining MOF,may be an exce llent precursor for s ingle-atom OER e lectrocatalysts d ue to its r ich and unifor m distr ib utio n o f cobalt species.I n pr inc ip le,Co ions are fully coordinated?except for those on the sur faces?in ZIF-67 without accessib le s ites for e lectrocatalys is.One way to utilize this single-atom mater ia l as e lectrocatalysts is to remove so me of the liga nds attached to Co ato ms to create coord inate ly unsaturated meta l s ites?CUMSs?as the cata lytic centers for OER.Here in,we have created CUMSs in ZIF-67 through die lectr ic barrier d ischar ge?DBD?p las ma etching.The CUMSs act as exce lle nt catalytic centers for OER with a promis ing e lectrocata lytic activity,eve n comparable to the prec io us RuO₂.Interestingly,the OER activity o f the CUMSs is revers ib le by supp le me nting the miss ing liga nds.Our dens ity-functio na l theory calc ulations a lso demo nstrated the contr ib utio n of the unsaturated meta l s ites to the high catalytic activity for OER.?3?The inter face between Pt nanopartic les and support mater ia ls is of cr itica l importa nce for tuning the electrocata lytic properties.The phys ica l and che mica l character istics of meta l oxide would influe nce the e lectronic and phys ica l interactio ns with Pt nanopartic les.Engineer ing the inter face interactio n between Pt and CeO₂ ma y be an effective way to mod ulate the electrocata lytic activity for electro-oxidation of methano l?MOR?.Here in,ceria na norods with ric h oxyge n vacanc ies?Vo?and roughness sur face ha ve been ind uced by plas ma sur face engineer ing,used as Pt support.For the specia l property of cer ia,the partic le size and dispers ion o f Pt nanopartic les could be well mod ified,the interaction o f Pt and creia are a lso re gulated.Intereastingly,the abundant Vo on cer ia sur face a fford surp lus electro ns,whic h would tra ns fer to the sub-surface with decreased Ce va lence in the sub-sur face o f CeO ₂,and cha nge the e lectron trans fer between Pt and ceria,increase the electron dens ity of Pt.Due to uniq ue electro n structure of Pt and CeO _2,MOR catalytic activit y and durab ility of the electrocata lyst are significa nt enha nced.Based on the above research,this thes is success fully c lar ifies the rela tions hip between defect-charge-catalytic per for ma nces us ing model cata lyst.Thro ugh the constructio n o f unsatura ted coord inatio n s ites o f MOFs-based catalysts,the regulation o f catalytic char ge by co-cata lys ts,it provides a new s ight for the design and preparation of optimal catalysts.