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Ад­со­р­б­ция и оки­с­ле­ние мо­но­ок­си­да угле­ро­да (СО) на ме­та­лли­че­с­ких эле­к­т­ро­дах — про­цесс пе­р­ви­ч­ной ва­ж­но­с­ти в ра­з­ви­тии ни­з­ко-­те­м­пе­ра­ту­р­ных по­ли­ме­р­ных то­п­ли­в­ных эле­ме­н­тов. То­п­ли­в­ные эле­ме­н­ты, ос­но­ван­ные на оки­с­ле­нии пе­ре­ра­бо­та­но­го во­до­ро­да, ко­то­рый со­де­р­жит не­бо­ль­шое ко­л­ли­че­с­т­во СО в каче­с­т­ве при­ме­си, а так же эле­ме­н­ты, ра­бо­та ко­то­рых ос­но­ва­на на не­по­с­ред­с­т­вен­ном оки­с­ле­нии ме­та­но­ла, стра­да­ют от от­ра­в­ле­ния СО. Та­ким об­ра­зом, суще­с­т­ву­ет ин­те­рес в ра­з­ви­тии ано­д­ных ка­та­ли­за­то­ров, ко­то­рые или ад­со­р­би­ру­ет очень ма­ле­нь­кое ко­ли­че­с­т­во СО (и в то же вре­мя все еще спо­со­б­ны оки­с­лять во­до­род в до­пу­с­ти­мых пред­елах), или спо­со­б­ны оки­с­ля­еть СО при бо­лее ни­з­ких по­те­н­ци­а­лах.

В на­сто­я­щей ра­бо­те пред­ста­в­ле­ны ре­зуль­та­ты ab initio ра­с­че­тов ме­то­дом те­о­рии фу­н­к­ци­о­на­ла пло­т­но­с­ти (DFT) вза­и­мо­дей­с­т­вия СО и ОН с чи­с­ты­ми ме­та­лла­ми, би­ме­тал­ли­че­с­ки­ми по­ве­р­х­но­с­тя­ми и си­с­те­ма­ми с над­сло­ем. Бы­ли изу­че­ны та­кие свой­с­т­ва, как гео­ме­т­рии ад­со­р­ба­тов, ча­с­то­ты ко­ле­ба­ний, эне­р­гии ад­со­р­б­ции ча­с­тиц на по­ве­р­х­но­с­ти, а та­к­же пу­ти ре­а­к­ци­и. В ка­че­с­т­ве мо­де­ль­ных бы­ли вы­б­ра­ны Pt(111), Pt(110) и Au(110) по­ве­р­х­но­с­ти. PtRu, PtMo и спла­вы PtSn ис­по­ль­зо­ва­лись как мо­де­ли би­ме­тал­ли­че­с­ких по­ве­р­х­но­с­тей. Эффект по­ве­р­х­но­с­т­ной се­г­ре­га­ции был та­к­же изу­чен на ра­з­ли­ч­ных по­ве­р­х­но­с­тях (Ru, Ni, Pd, Rh, Ir) с Pt-на­д­с­ло­ем. Ис­хо­дя из ре­зуль­та­тов ра­с­че­тов ко­а­д­со­р­б­ции СО и ОН на по­ве­р­х­но­с­тях Pt(111) и Au(110), пред­ло­жен об­щий ме­ха­низм оки­с­ле­ния СО мо­ле­ку­лой ОН (или О-­со­де­р­жа­щи­ми ча­с­ти­ца­ми на по­ве­р­х­но­с­ти). На­ко­нец, на Pt(111) и Pt2Ru(111) по­ве­р­х­но­с­тях бы­ла изу­че­на ко­а­д­со­р­б­ция мо­ле­кул во­ды (H2O) и ОH.

Все ра­с­че­ты бы­ли вы­по­л­не­ны в ра­м­ках па­ке­та про­грам VASP. По­ве­р­х­но­с­ти бы­ли смо­де­ли­ро­ва­ны с ис­по­ль­зо­ва­ни­ем пе­ри­оди­ч­но­с­ти. Ана­лиз ко­ле­ба­те­ль­ных ча­с­тот был сде­лан в про­гра­м­мах AnharmND и Gaussian98.



ЗМІСТ/Contents



Chapter 1

Introduction............................................................................................................................................................ 6

1.1. Fuel cells........................................................................................................................................................... 6

1.2. CO adsorption and oxidation on platinum......................................................................................................... 10

1.3. Theoretical method.......................................................................................................................................... 14

1.3.1.. General overview of DFT method.......................................................................................................... 14

1.3.2.. Software and computational models....................................................................................................... 20

1.4.. Scope of this work.......................................................................................................................................... 22



Chapter 2

Periodic density functional study of CO and OH adsorption on Pt-Ru alloy surfaces:

implications for CO tolerant fuel cell catalysts .................................................................................................. 27

2.1. Introduction..................................................................................................................................................... 27

2.2.. Computational methods................................................................................................................................... 29

2.3. Results and Discussion..................................................................................................................................... 32

2.3.1.. Adsorption of CO................................................................................................................................. 32

2.3.2.. Adsorption of OH................................................................................................................................. 39

2.4. Mechanistic implications and conclusions.......................................................................................................... 43



Chapter 3

Quantum-chemical calculations of CO and OH interacting with bimetallic surfaces ....................................... 49

3.1.. Introduction..................................................................................................................................................... 49

3.2.. Computational methods................................................................................................................................... 52

3.3.. Results and Discussion..................................................................................................................................... 54

3.3.1.. CO and OH on PtRu............................................................................................................................ 54

3.3.2.. CO on Pt monolayer systems................................................................................................................ 57

3.3.3.. CO and OH on PtMo........................................................................................................................... 60

3.3.4.. CO and OH on Pt3Sn(111)................................................................................................................... 61

3.3.5.. CO and OH on Pt(110) and Pt3Sn(110)............................................................................................... 63

3.4.. Conclusions..................................................................................................................................................... 66



Chapter 4

Density Functional Theory study of the oxidation of CO by OH on Au(110) and Pt(111) surfaces................ 71

4.1. Introduction..................................................................................................................................................... 76

4.2.. Computational Methods................................................................................................................................... 76

4.2.1.. Slab Approach...................................................................................................................................... 78

4.2.2.. Cluster Approach.................................................................................................................................. 78

4.3.. Results and Discussion..................................................................................................................................... 79

4.3.1.. Au(110)................................................................................................................................................ 79

4.3.1.1. Adsorption of CO and OH on Au(110).................................................................................... 79

4.3.1.2. Adsorption of COOH on Au(110)........................................................................................... 81

4.3.1.3. Formation of COOH from CO and OH on Au(110)................................................................ 83

4.3.2.. Pt(111)................................................................................................................................................. 85

4.3.2.1. Adsorption of CO and OH on Pt(111)..................................................................................... 85

4.3.2.2. COOH adsorption on Pt(111)................................................................................................. 86

4.3.2.3. Formation of COOH from CO and OH on Pt(111).................................................................. 87

4.4.. Mechanistic implications and Concluding Remarks............................................................................................ 88



Chapter 5

Co-adsorption of water and hydroxyl on a Pt2Ru surface ................................................................................. 97

5.1. Introduction..................................................................................................................................................... 97

5.2. Computational methods................................................................................................................................... 99

5.3. Results and Discussion................................................................................................................................... 101

5.3.1.. Adsorption of OH and H2O separately............................................................................................... 101

5.3.2.. Coadsorption of OH and H2O............................................................................................................ 102

5.4.. Conclusions................................................................................................................................................... 105



Summary....................................................................................................................................................... 108