PHY563 – 20/01/2021

PHY 563 – PC2Catalysis

Jean-françois Guillemoles

Nathanaelle Schneider

UMR-IPVF 9006

CNRS

PHY563 – 20/01/2021

Title-authors-DOI-Abstract

Introduction

context/questions adressed/

Results – Discussion – Conclusion

Methods

References

Supplementary informations

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Presentation of Paper Outline

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Publication

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General questions:- Which type of publication is it?- How important/relevant is the journal? the article?

Specific questions: - What is the field? - What are the main claims of the paper?- Which methods and materials? Preparation (principle, pro/cons) and Characterization (principle, ex-/in-situ, what is observed)- What is new since the publication of the article?

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Publication

Impact factor = 14,588 (2019)cited 12 time (Google scholar on 20/01/2021)

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General questions:Which type of publication is it? How important/relevant is the journal? the article?

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Publication

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Specific questions: - What is the field? - What are the main claims of the paper?

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Catalysis – significance and main applications

•Academia

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Fig. 1 Subject area breakdown of Catalysis Science & Technology's 2014 published articles.

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publication

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General questions:- Which type of publication is it?- How important/relevant is the journal? the article?

Specific questions: - What is the field? - What are the main claims of the paper?- Which methods and materials? Preparation (principle, pro/cons) and Characterization (principle, ex-/in-situ, what is observed)- What is new since the publication of the article?

- Critical view on the article

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?

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Identify fabrication techniques

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Publication

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Preparation methods:- CNT? Unzipping step? N-doping?

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•Catalytic process

•VLS process• CHx decomposition and C

dissolution in the NP

• Temp. gradient drives C precipitation on the cold side 11

CNT Synthesis

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Local configuration of active sites (atomic models)

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Simplified version of Schrodinger equation

Solves a many body problem as a function of electron densityonly (instead of a function of coordinates of all electrons)

In principle exact, but in practice approximation have to beused

Especially used for ground states

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DFT

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Density Functional Theory (DFT)

•Electron density is the basic variable from which all terms in the Schrodinger equation can be determined uniquely at ground state (Hohenberg-Konh 1965)

•Variational principle applies on r:

External + nuclear action r(r)

Universal functional F(r(r))

Advantage: a single function of space (instead of one/e-)

•Euler-Lagrange equations

LDA approximation

PHY563 – JF Guillemoles 14

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Can you name some?

How are claims justified?

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Identify Material characterization techniques

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Caracterisation:- What are the main techniques used to characterize the microstructure of the

system?

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XRD= X-Ray Diffraction

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Diffraction – Braggs’s law

d = spacing between diffractingplanesΘ = incident anglen = integerλ = beam wavelength (?)

Peak height : proportional to the number of incident electron, to the size and number of crystallitesPeak position: depends on the type and the parameter of the primitive cell ( + constraints in the material)Peak width : depends on internal micro-constraints and the size of the crystalline coherence

F. Pan et al. ACS Nano, 2020S. I.

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Structure identification: XRD

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(200)

(220)

(111)

(311)

Exemple: XRD zinc-blende structure- Cubic face-centered- Two atoms per primitive cell

A (0,0,0) B (¼, ¼, ¼)

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XRD

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2ΘΘ

Bragg-Brentano Cubic: (1/dhkl)² = (h²+k²+l²)/a²

Preferential orientation: (111)

d111 = λ/(2 sinθ) = a√3 = 3.12 Åa = 1.80 Å

sample

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Secondary

electrons:

Low energy

Superficial layers

> Topology

Back-scattered

electrons:

High energy

Atomic number

sensitive

> Chemical

homogeneity

Auger

electrons:

Very low energy

> Surface,

Chemical

bounds

X-rays

Low energy

Superficial layers

> Atomic

composition,

(EDX analysis)

Interaction matter – electrons

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SEM

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Scanning Electron Microscopy: SEM

• Resolution : nm scale• Conditions: vacuum, ambient T, pre-treatments• Ex: insulating part (charged) appears bright and conducting part appears dark

Scintillator+ photomultiplicator

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TEM

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Electronic Microscopy: TEM (Transmission Electron Microscopy)

• Transmitted electrons• High vacuum system (10-4 Pa) to increase

electron mean free path

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Electronic Microscopy

TEM (Transmission Electron Microscopy)

and SEAD (Selected Area Electron Diffraction)

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PrincipleWhat is evidenced ?

F. Pan et al. ACS Nano, 2020S. I.

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Electronic Microscopy

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TEM• Transmitted electrons• High vacuum system (10-4 Pa) to increase

electron mean free path

SAED• Crystallographic technique that can be

performed inside TEM• Atoms act as diffraction grating to the

electrons• Similar to XRD but smaller samples can be

analysed (100 nm vs. cm)• Nanoparticles: diffraction rings

TEM (Transmission Electron Microscopy)

and SEAD (Selected Area Electron Diffraction)

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Scanning Transmission Electron Microscopy : STEM

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HAADF: high angle annular dark-field

Aberation corected, gives a high contrast , atomic resolution image

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Caracterisation:- What are the main techniques used to characterize the system?

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Based on Langmuir’s isotherms theory:

• Amount of adsorbed gas/g depends on T, P, gas and specific surface

• Law of mass action

N2 @77K often used as reference, fit to theory determines specific volume

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Adsorption: BET (Brunauer, Emmett et Teller) model

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XPS =X-ray Photoelectron Spectroscopy

Wikipedia

• Stoichiometry• Impurities• Chemical environment: charge transfer, coordination, oxidation state

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XPS

XPS (X-ray Photoelectron Spectroscopy)

• Identification of Mn+ species present

• Information on the first coordination sphere

• Composition

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X-Ray Photoelectron Spectroscopy: XPS

From P. Schulz

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X-Ray Photoelectron Spectroscopy: XPS

From P. Schulz

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Caracterisation:- What are the main techniques used to characterize the system?

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Synchrotron tools

• Powerful tunablelight source

From IR to hard X Rays

•Based on acceleratedcharged particles

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Soleil@Saclay

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XANES, EXAFS

XANES (X-ray Absorption Near-Edge Spectroscopy) and EXAFS (Extended X-ray Absorption Fine Structure)

• Excitation source = synchrotron light

• XANES (or NEXAFS) : sensitive to electronic transitions within atoms => electronic state, oxidation state

• EXAFS = oscillations due to interferences with neighboring atoms (of a given atom)=> chemical environment, neighboring atoms (nature, number). Distribution of neighbors requires mathematical fitting

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XANES, EXAFS - publication

• Major peak at 1.5 1 backscattering of light atoms (C, O, N)

• Second peak at 2-3A C, N, O in second coordination sphere

• No M-M isolated metal centers

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Plasma torch (inductive plasma) to vaporise and decompose analyts in small ionized fragments

Mass spectrometry to identify atomic mass of single fragments

Very low concentration limit (1/1E15)

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Inductively coupled Plasme-Mass spectrometry : ICP-MS

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TOF-SIMS

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FUNDAMENTAL NOTIONS

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Questions

•Identify the catalytic reaction

•Activity (turn over frequency = TOF)

• Selectivity (Faradic efficiency)

• Stability (turn over number = TON)

• Support

(Hint: see figure 4)

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Advanced questions:

How is the selectivity measured?

How would TON and TOF be extracted?

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Reactions

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Can you write the CO2 reduction reaction?

CO2 + 2 H+ + 2 e- CO + H2O

The Hydrogen reduction reaction?

Can you see why the reaction is selective?

(Hint: see figure 6)

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Reaction pathways

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Catalytic systems :- Setup- What is the reaction catalyzed- Catalyic mechanism investigation – main claim

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CO2RR = Reduction of Carbon Dioxide Reduction REaction

CO2 CO, HCOOH, CH3OH, C2H4, ..

- electrocatalysis

- at similar potential than HER (Hydrogen Evolution Reaction)

- C=O very stable bond (E = 806 kJ.mol-1)

- catalyst

metal, metal oxides, chalcogenides, core-shell

Sn, Pb (HCOOC) // Au, Ag (CO) // Cu (4-12 e- products) // Pt, Ni (HER)

Molecular catalysts // Bioinspired catalysts: hemoglobin

M-N/C materials

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Field –CO2RR

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Catalysis – fundamental notions

•Catalysis = increase of chemical reaction rate due to the participation of an additional substance (catalyst) : thermodynamics / kinetics

PHY563 – N. Schneider 47

Ea = activation energy

= transition state

k = A.e-Ea/RT(Arrhenius)

o

oo

Catalyzed reaction : ≠ intermediates/ transition states

lower Ea

o = intermediate

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Catalysis – fundamental notions

•Different types of catalysis

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HETEROGENEOUS Cat. and reactants in different phasesHOMOGENEOUS Cat. and reactants in the same phase, usually liquid

(+) Good contact with reactants(+) Ease of characterization/tuning(-) Catalyst needs to be separated after the reaction(-) Difficult catalyst recovery

ENZYMATIC Cat. is an enzyme

(+) Most highly efficient systems(+,-) Highly specific

(+) Little difficulty in separating and recycling the catalyst(-) Lower effective concentration of catalyst

Ni Raney: Ni/Al

Wilkinson cat.: RhCl(PPh3)3

Polyneuridine AldehydeEsterase

catalyst

loading (mol%)

activity (mol.s-1, quantity converted/time, or TOF (turn-over frequency

selectivity ability to yield a particular product

stability TON (turn-over number)

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Catalysis – significance and main applications

•Industry90% of industrial processes are catalyzed

(1) Bulk chemicals • polymerisation (Ziegler-Natta)

• oxydation (nitric/sulfuric acid)

• hydrogenation (NH3 Haber-process, methanol)

• carbonylation (acetic acid, Monsanto-process)

(2) Fine chemicals• olefin metathesis

• Friedel-Craft

• asymmetric synthesis (pharmaceuticals)

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Catalysis – significance and main applications

(3) Energy processing

CO2 reduction

See PC

Fuel cells metal catalysts at both anode and cathode to catalyze half-reactions

commercial devices: Pt nanoparticles or Pt alloy supported on C black

« main obstacle for larger fuel cellcommercialisation »

research devices: doped C nanotubes, Ni-Cr, Ni-Al or Ni-O alloys

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Source: D. S. Ginley et al, Fundamentals of materials for energy and environmental sustainability-Cambridge University Press (2012)

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Catalysis – significance and main applications

(3) Energy processing

Catalytic converters

(petroleum exhaust)

51Source: Handbook of Heterogeneous Catalysis, Wiley, 2008

Reduction (Rh) : NOx N2

Oxydation (Pt) : CO CO2 , HC CO2 + H2Oλ probe + cordierite support + Al2O3 washcoat + CeO2 O2 storage promoters + Pt + Rh

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Catalysis – significance and main applications

(3) Energy processing

Catalytic converters

(petroleum refining)

alkylation, cracking, naphta and steam reforming (HC syn-gas)

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( CO, H2 )

( CO, H2 )

( H2O, CH4 )

steam reforming

Water-gas-shiftH2O + CO CO2 + H2

Adjusted syn-gas, H2/CO=2

syn-gas, H2/CO=0.7

Hydrocarbons + H2OFischer-Tropsch

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Catalysis – significance and main applications

(3) Energy processing

Fischer-Tropsch

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History

• 1923 : patent from Franz Fischer and Hans

Tropsch (Kaiser-Wilhelm-Institut für

Kohlenforschung, Mülheim an der Ruhr)

• WWII : ersatz fuel (90% plane, 25% automobile)

• 50’s : South Africa

• 70’s : Regain of interest due to oil price increase

• currently : Sasol, PetroSA, Linc Energy, Shell

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Catalysis – significance and main applications

(3) Energy processing

Fischer-Tropsch

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Sasol-Qatar Petroleum Oryx plant

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Catalysis – significance and main applications

(3) Energy processing

Biomass

conversion

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biomass

SyngasSynthetical gas, {CO + H2}

MethanolCH3OH

Cat. Cu/ZnO440°C, 50 atm

GasificationControlled amount of O2

Hydrocarbon chainsCnH2n+2

Fischer-Tropf process

Fischer-Tropf processtypically catalyzed by Co, FeT 300°C

challenges: - control n value- catalyst deactivation- …

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Catalysis – significance and main applications

(3) Energy processing

Biomass

conversion

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Simulation of reaction sites and pathways: DFT

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Simplified version of Schrodinger equation

Solves a many body problem as a function of electron densityonly (instead of a function of coordinates of all electrons)

In principle exact, but in practice approximation have to beused

Especially used for ground states

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DFT

PHY563 – 20/01/2021

Density Functional Theory (DFT)

•Electron density is the basic variable from which all terms in the Schrodinger equation can be determined uniquely at ground state (Hohenberg-Konh 1965)

•Variational principle applies on r:

External + nuclear action r(r)

Universal functional F(r(r))

Advantage: a single function of space (instead of one/e-)

•Euler-Lagrange equations

LDA approximation

PHY563 – JF Guillemoles 59

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DFT

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Aim: separating chemicals in a complex sample• sample pass in a gas stream at different rates

depending on their properties and their interaction with the column filling ('stationary phase‘)

• They are separated according to their time to exit ('retention time')

• At exit they are detected and identified electronically.

Detection

• flame ionization detector (FID)

• thermal conductivity detector (TCD)

• Mass spectrometer (MS)

• Vacuum ultraviolet (VUV)

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Gas Chromatography

Wikipedia

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Bibliography: Catalysis

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