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Good morning Dr Sheela. First, I'm really sorry for posting this late. I won't repeat this again Dr.

Now, my question is how does surface acidity or basicity of a metal oxide catalyst influence selectivity in condensation reactions?

Thank you Dr.

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NUR AFIQAH BINTI AHMAD RUSLI (A21SC0210)

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NUR AFIQAH BINTI AHMAD RUSLI (A21SC0210)

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Assalamualaikum and hi Dr. Sheela.

I would like to ask why transition metals like Pt, Pd, or Ni are commonly used for surface catalysis in hydrogenation reactions, whereas metal oxides are more suited for oxidation reactions?

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Hi Dr. Sheela, I have a question regarding catalysis on metal and metal oxide surfaces. I would like to understand how the electronic structure of a metal or metal oxide surface influences its catalytic behavior. Specifically, how do factors such as the density of states, and d-band center affect the activity and selectivity of a catalyst in surface reactions?

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MUHAMMAD ZAHID AMMAR BIN YUS RIZAL (A20SC0173)

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MUHAMMAD ZAHID AMMAR BIN YUS RIZAL (A20SC0173)

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Assalamualaikum Dr, I want to ask regarding Miller Indices. From what I understand is Miller Indices is the way we cut the compound. So does it means that for an example, I have a cube of Fe catalyst, so do I cut it using a knife or saw according to the miller indices I want? Or its actually a small Fe cube that we cut using some special machine? If it is a special machine use to cut the small Fe cube, what is the machine name?

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Good morning Dr Sheela, I would like to ask on how does the nature of lattice, adsorbed, and surface oxygen species influence the oxidation mechanism of hydrocarbons on metal oxide catalysts like V₂O₅ or Fe₂O₃?

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Assalammualaikum and hi Dr Sheela.

I would like to can the platinum be substituted with another noble metal that can act as electron trap? As I know, platinum is quite expensive and maybe there is another noble metal that can replace the Pt.

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Assalamualaikum and Hi Dr. Sheela,

How do crystallographic defects like oxygen vacancies affect both the catalytic activity and selectivity of a metal oxide surface? Can too many defects become detrimental?

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Assalamualaikum and Hi Dr. Sheela,

I’ve read that TiO₂ can break down pollutants using light, but how does it actually work if I mixed into soil. Does it still react the same way ?

If TiO₂ is added to soil, does it help clean up harmful chemicals and can it help improve soil health, or is it mainly used for pollution control ?

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NUR ATHIRAH ALIAH BINTI JAMIL (A21SC0222)

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NUR ATHIRAH ALIAH BINTI JAMIL (A21SC0222)

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Assalamualaikum Dr Sheela. Since noble metal doping (like Pt in TiO₂) can enhance charge separation by trapping electrons, is there a trade-off in terms of surface area or light absorption that limits how much metal we should add?

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MOHAMMAD KHAIRUL HAIQAL BIN OSMAN (A21SC0141)

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MOHAMMAD KHAIRUL HAIQAL BIN OSMAN (A21SC0141)

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Assalamualaikum, Dr Sheela, I want to ask, how do people actually use Miller indices when choosing or making catalyst surfaces in industries, and why does knowing about Miller indices help make catalysts work better in real life?

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BALQISNURAIN BINTI MOHD ZAIDI (A21SC0039)

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BALQISNURAIN BINTI MOHD ZAIDI (A21SC0039)

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Hi Assalamualaikum Dr Sheela. How is semiconductor photocatalysis applied in treating water and air pollution, and what types of pollutants can it effectively degrade? In what ways does this method compare to conventional treatment techniques in terms of efficiency, cost, and environmental impact?

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Good day Dr Sheela, I would like to ask about Catalysis on Metal Oxides Surfaces.

One of the defects of n-type semiconductors is Anion vacancy with trapped electrons.

1. Is it meant that oxygen in metal oxide is always missing, left behind its electrons in the vacancy?

2. If yes, when the metal oxide is doped with other material such as liquid crystal, can these free electrons interact with LUMO of liquid crystal to form hybridised state that alter the energy bandgap of liquid crystal?

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Assalamualaikum Dr sheela. I would like to ask in the slides, both ZnO and TiO₂ are mentioned as photocatalysts. Is there a specific reason why TiO₂ is more commonly used in industrial applications despite ZnO ?

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Assalamualaikum and Hi Dr.Sheela,

I want to ask on transition metal doping.Why do certain transition metals like Fe³⁺ enhance photocatalytic activity while others like Cr³⁺ reduce it. What causes this difference at the electronic level?.

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Hi , Dr Sheela. Here is my question, In photocatalysis, how does doping TiO₂ with transition metals like Fe³⁺ improve efficiency, while Cr³⁺ has the opposite effect? What determines whether a dopant suppresses or enhances electron-hole recombination?

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Assalamualaikum and hi Dr. Sheela,

may i know how does adding metals like platinum or iron to TiO₂ help improve the photocatalytic process, and how do we know how much metal to add without making it less effective?

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Good day, Dr. Sheela. I would like to ask: In the ZnO/TiO₂ coupled semiconductor system discussed in the slides, how does the alignment of the conduction and valence bands between ZnO and TiO₂ govern the charge transfer mechanism?

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MUHAMMAD AIMAN AQIL BIN MUHAMAD ERI (A21SC0147)

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MUHAMMAD AIMAN AQIL BIN MUHAMAD ERI (A21SC0147)

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Hi Assalamualaikum Dr Sheela.

I want to ask about the n-type and p-type semiconductor. Is there any significant difference between that two type semiconductor in term of their catalytic activity. Also, between those two, what do you prefer?

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Hi Dr Sheela, I would like to ask although catalytic converters are effective at reducing harmful gases in automobile exhaust, their performance can be influenced by several external factors. What are some common conditions or materials that reduce the efficiency of catalytic converters, and how do they interfere with the catalytic reactions?

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Good day Dr. Sheela,

so i want to ask why does the same metal work differently depending on the surface, isn’t it still the same metal?

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Hi Dr Sheela, how do reaction conditions like temperature, pressure and pH affect catalytic performance on metal surfaces?

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TIARA ALIYAH BINTI ABDULL RAHMAN (A21SC0377)

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TIARA ALIYAH BINTI ABDULL RAHMAN (A21SC0377)

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Assalamualaikum and hi dr sheela. I want to ask in photocatalysis using TiO₂, electron-hole recombination reduces efficiency. Why is this not a concern in metal catalysts such as Pt for hydrocarbon reforming?

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NURUL IZZATI BINTI MUAHAMMAD AFDHAL (A21SC0316)

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NURUL IZZATI BINTI MUAHAMMAD AFDHAL (A21SC0316)

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Hi dr Sheela, can i ask how do we balance between increasing bandgap energy for stability and keeping it low enough for visible light activation?

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NURUL AMIRA NAJWA BINTI MOHAMAD AZMAN (A21SC0303)

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NURUL AMIRA NAJWA BINTI MOHAMAD AZMAN (A21SC0303)

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Hi Dr Sheela. My question is are there any interdisciplinary approaches (combining chemistry, materials science, and engineering) that are particularly promising for advancing catalysis technology?

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Assalamualaikum Dr

Dr., what would happen if the metal surface used in a catalyst becomes rough or damaged over time? Will it affect the reaction?

What risks or by products might occur if photocatalysts like TiO₂ break down complex pollutants in wastewater? Are all products safe

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Syaza Hani Binti Khairi Anuar (A21SC0371)

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Syaza Hani Binti Khairi Anuar (A21SC0371)

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Assalamualaikum and hi Dr Sheela,

Here is my question, what are some limitations or challenges currently faced in photocatalytic processes for industrial or municipal use?

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SYAFIQA ADRIANA BINTI MOHD SUHAIMI (A21SC0368)

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SYAFIQA ADRIANA BINTI MOHD SUHAIMI (A21SC0368)

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Assalammualaikum Dr. Sheela, i would like to ask if there are any environmental or health concerns associated with the use of certain metal oxide catalysts, especially at the industrial scale?

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Assalamualaikum Dr. Sheela,

My question is why are some metal surfaces more active in catalysis even though they have the same chemical composition?

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Good day Dr Sheela

As we know, a band gap energy greater than 3.2 eV is typically required for UV light absorption. But how can the band gap of a photocatalyst be determined?

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Assalamualaikum Dr. Sheela. I hope you're doing well. I would like to ask about the influence of surface geometry on catalytic reactions. Specifically, how do different crystallographic planes of iron influence the adsorption and activation of nitrogen molecules during ammonia formation? Could this suggest a broader trend about how surface topology affects reaction mechanisms?

Also, I’m interested in the role of semiconductor materials in environmental cleanup. How do the positions of the valence and conduction bands in TiO₂ facilitate the generation of oxidative species during photocatalytic water treatment? And why is the anatase structure generally regarded as more reactive than the rutile form in such applications?

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Assalamualaikum and hye dr , i wanna ask which is more environmentally sustainable in industrial catalysis whether using pure metal catalysts or metal oxide-based catalysts based on their availability, toxicity, and regeneration?

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Good day Dr. Sheela,

Most studies describe catalyst surfaces as static, but during real reactions, do catalyst surfaces undergo restructuring, shape changes, or even break apart? If so, how does this dynamic behavior influence their catalytic activity and the reaction mechanism?

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Good day Dr Sheela,

Is the typical reaction mechanisms (e.g., Langmuir-Hinshelwood & Eley-Rideal) differ or remain similar for reactions occurring on (a) metal surfaces and (b) metal oxide surfaces?

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NUR SYAFIQAH BINTI KAMARUDDIN (A21SC0260)

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NUR SYAFIQAH BINTI KAMARUDDIN (A21SC0260)

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Assalamualaikum and Hi Dr. Sheela, how can surface defects on a catalyst act as active sites or recombination centers? Also, why do stepped or kinked surfaces often show higher activity even though they’re technically defects?

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Hi Good Day Dr. Sheela. My question is in the case of photocatalysis using mixed metal oxides, how do we determine which metal ion acts as the active site, especially when both contribute acid–base or redox properties?

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Good day Dr. Sheela,

How do kinked and stepped surface sites on a catalyst influence its catalytic activity and selectivity compared to flat surface sites?

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Nur Nabila Natasya Binti Mohamad Nazri (A21SC0247)

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Nur Nabila Natasya Binti Mohamad Nazri (A21SC0247)

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Assalamualaikum Dr. Sheela, I would like to ask how do different surface facets like (111) and (100) influence the catalytic activity of a crystallite? For example, does the difference in atomic arrangement on these planes affect how molecules adsorb or react? And how does this apply to shapes like cubo-octahedrons or icosahedrons?

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NUR IZZATI FARHANAH BINTI ABD KADIR (A21SC0243)

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NUR IZZATI FARHANAH BINTI ABD KADIR (A21SC0243)

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Assalammualaikum Dr. Sheela. I want to ask how do the Miller indices (e.g., (111), (100), (110)) of iron surfaces influence ammonia synthesis, and what does this imply about the relationship between atomic surface structure and catalytic efficiency?

My second question is what roles do the conduction band, valence band, and hydroxyl radicals play in the degradation of organic pollutants in water treatment? Why is anatase TiO₂ preferred over the rutile form?

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Good day Dr Sheela, I am curious about γ-alumina. γ-alumina has both acidic and basic surface properties. If I want to use it in a reaction that needs strong acid sites, what should I do to make it more acidic?

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salam sejahtera dr sheela

1. Why is Pt(111) more effective for aromatization reactions (e.g., n-hexane → benzene), while Pt(100) is better for isomerization reactions (e.g., isobutane → n-butane)?

2. Why is Fe³⁺ a suitable dopant for TiO₂ photocatalysts, while Cr³⁺ increases recombination? Discuss the electronic interactions and propose an optimal doping concentration for Fe³⁺.

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MOHAMAD SALMAN BIN MOHAMAD SABRI (A21SC0136)

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MOHAMAD SALMAN BIN MOHAMAD SABRI (A21SC0136)

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Hi Dr Sheela i want to ask why fast electron-hole recombination bad for efficiency of a semiconductor photocatalyst ?

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Hi Dr Sheela.

How surface defects can act as both catalytic active sites and potential deactivation points?

Why might stepped and kinked surfaces be more catalytically active than flat surfaces, even though they represent defects?

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Assalamualaikum Dr. Sheela.

May I ask, what does it mean by 'the Fermi levels of the metal and semiconductor align causing electrons to flow to the metal from the semiconductor.'

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Hi Dr Sheela, good day to you. I have a question, does catalyst can degrade plastic (through photocatalysis or not) in the environment?

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Good day, Dr Sheela. Regarding the topics, there is a question I would like to ask:

Can Dr explain a bit of detail on gamma alumina, which is on slide 10, pages 16-18? Because I'm confused and couldn't catch up with the concept of Lewis acid and Bronsted acid in the case of gamma alumina.

Thank you Dr.

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Good day Dr Sheela. My question is what is meant by the defect spinal structure in γ-alumina and how it affects catalysis?

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Hi Dr Sheela. I have a question regarding catalytic converter. Would you mind explain the air-to-fuel ratio in a simple sentence?

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Hi Dr Sheela, here is my question

-How does surface area and porosity of a metal catalyst affect its performance?

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FATIN SHAHIRAH BINTI ABD HADI (A21SC0081)

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FATIN SHAHIRAH BINTI ABD HADI (A21SC0081)

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Assalamualaikum Dr. Sheela,

My question is can dr describe how the structure and morphology of platinum catalysts (e.g., flat Pt(100), Pt(111), stepped Pt(755), kinked (10,8,7)) influence their catalytic performance in hydrocarbon conversion reactions such as aromatization and isomerization.

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Hi, Dr. Sheela. I have a question regarding metal oxides and my FYP project. My FYP project involves making an electrochemical sensor. During the fabrication process, ZnONPs (zinc oxide nanoparticles) are deposited on FMWCNTs (functionalized multi-walled carbon nanotubes) on the electrode. ZnONP acts as a catalyst, increasing the electron transfer at the electrode, thereby improving the current response. Therefore, I am curious how it catalyzes the electron transfer? Is it because it is a semiconductor and has a higher surface area for electron transfer? In addition, I am also curious that whether the adsorption of ZnONPs on FMWCNTs is due to electrostatic interaction?

Thank you Dr.

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1. How is photocatalytic degradation a more effective method for wastewater treatment compared to conventional methods, and why does biological treatment is still the most widely used method despite these advancements?

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Hi good day Dr sheela, i question regard the slide (9) page 28. What is the meaning of high pressure drop

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Hi Dr Sheela, here is Lum. Thank you very much for preparing this session for us so we could study the note more intensively to generate a question. I have the same doubt with Fadzil, which is about how the surfaces affected the catalysis. Square and hexagonal are cleared, but it's hard for me to imagine on kinked and stepped. While another question is on the alignment of Fermi levels of semiconductor and noble metal (Pt). Noble metal is a conductor, which has a very different energy level as compared to semiconductor. My doubt is can Fermi level of metal and semiconductor be aligned if the metal is only added onto the semiconductor without any reaction? As my concept is the change of an elemental could only be happened if there is any chemical reaction. Therefore, I confused when read this.

I look forward to receiving any answer from the other coursemates or Dr Sheela. Lastly, thank you Dr Sheela and anyone for your time on read my questions and any attempt to solve my doubts.

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1. How the transition metal impurity ions affect the photocatalyst properties of TiO₂?

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Hi Dr Sheela

My question is why ROR of aromatization oof n-alkane is faster by (111) Pt but slower in isomerization of isobutanr according to slide 9. Structure of HC affects the catalyst activity?

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Assalamualaikum Dr Sheela, I would like to ask about why are the catalyst supported (page 30 note 9) specifically on the electronic factors part. I find this part a bit difficult to understand. If possible can you give some example? Thank you Dr Sheela

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MUHAMMAD FADZIL BIN MAT ZAIN (A21SC0158)

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MUHAMMAD FADZIL BIN MAT ZAIN (A21SC0158)

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1. I get that flat, stepped, and kinked surfaces affect catalysis, but how exactly do steps and kinks make the surface more reactive? Is it because they give more active sites or something?

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Good day Dr Sheela, my questions based on slides 9 & 10 are listed below.

1. Why do stepped and kinked Pt surfaces exhibit higher catalytic activity than flat surfaces, considering their lower atomic coordination and abundance of unsaturated surface sites?

2. Among lattice oxygen, adsorbed oxygen, and surface oxygen, which form(s) play the dominant role in hydrocarbon oxidation?