ESSEE 4 4 th European Summer School ELECTROCHEMICAL

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ESSEE 4 4 th European Summer School ELECTROCHEMICAL ENGINEERING PRINCIPLES of ELECTROCATALYSIS Sergio Trasatti

ESSEE 4 4 th European Summer School ELECTROCHEMICAL ENGINEERING PRINCIPLES of ELECTROCATALYSIS Sergio Trasatti Department of Physical Chemistry and Electrochemistry University of Milan, Italy University of Milan, Department of Physical Chemistry & Electrochemistry

POTENTIALITY OF ELECTROCHEMISTRY • Conversion of chemical energy into electrical energy (power sources) •

POTENTIALITY OF ELECTROCHEMISTRY • Conversion of chemical energy into electrical energy (power sources) • Conversion of electrical energy into chemical energy (electrolyzers) University of Milan, Department of Physical Chemistry & Electrochemistry

Electrolyzers E R P Batteries Fuel Cells R R E E P P University

Electrolyzers E R P Batteries Fuel Cells R R E E P P University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCHEMICAL PROCESS R + ne = P AMOUNT OF ELECTRICITY Additional specific reactant University

ELECTROCHEMICAL PROCESS R + ne = P AMOUNT OF ELECTRICITY Additional specific reactant University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTRICAL ENERGY Power sources: Production Electrolyzers: Consumption V x Q V x I x

ELECTRICAL ENERGY Power sources: Production Electrolyzers: Consumption V x Q V x I x t AIM Power sources Maximum I with maximum V Electrolyzers Maximum I with minimum V University of Milan, Department of Physical Chemistry & Electrochemistry

INTENSIVE ELECTROCHEMICAL PROCESSES Process Production Mt/y Consumption k. Wh/kg Chlor-Alkali 32 3 Aluminium 16

INTENSIVE ELECTROCHEMICAL PROCESSES Process Production Mt/y Consumption k. Wh/kg Chlor-Alkali 32 3 Aluminium 16 13 Chlorate 1. 7 5 University of Milan, Department of Physical Chemistry & Electrochemistry

Electrochemical Polarization V = E ± overpotentials Overpotential: Energy dissipation to overcome reaction resistances

Electrochemical Polarization V = E ± overpotentials Overpotential: Energy dissipation to overcome reaction resistances University of Milan, Department of Physical Chemistry & Electrochemistry

COMPONENTS OF ΔV V = E ± S ± IR ± DVt (+) for

COMPONENTS OF ΔV V = E ± S ± IR ± DVt (+) for electrolyzers (-) for power sources University of Milan, Department of Physical Chemistry & Electrochemistry

THE ΔE TERM Meaning Thermodynamic potential difference Strategy It can only be modified by

THE ΔE TERM Meaning Thermodynamic potential difference Strategy It can only be modified by modifying the nature of electrode processes Example Chlorine-hydrogen cell ΔE = 1. 35 – (-0. 84) = 2. 19 V Chlorine-oxygen cell ΔE = 1. 35 – 0. 39 = 0. 96 V University of Milan, Department of Physical Chemistry & Electrochemistry

THE IR TERM Meaning Ohmic drops in the electrodes and in the solution between

THE IR TERM Meaning Ohmic drops in the electrodes and in the solution between the electrodes Strategy - Increase the conductivity of electrode materials. - Decrease the interelectrode distance. - Avoid formation of bubble curtains at electrodes. University of Milan, Department of Physical Chemistry & Electrochemistry

THE IR TERM IR j an j cat University of Milan, Department of Physical

THE IR TERM IR j an j cat University of Milan, Department of Physical Chemistry & Electrochemistry

BUBBLE EFFECT Ohmic drop Surface blocking Mass transfer University of Milan, Department of Physical

BUBBLE EFFECT Ohmic drop Surface blocking Mass transfer University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTRODE OHMIC DROP Sn. O 2 + Ir. O 2 University of Milan, Department

ELECTRODE OHMIC DROP Sn. O 2 + Ir. O 2 University of Milan, Department of Physical Chemistry & Electrochemistry

THE Ση TERM Meaning Sum of anodic and cathodic overpotentials Strategy Search for materials

THE Ση TERM Meaning Sum of anodic and cathodic overpotentials Strategy Search for materials with low values of overpotential University of Milan, Department of Physical Chemistry & Electrochemistry

THE ΔVt TERM Meaning Unstability: increase with time of the ΔV applied to the

THE ΔVt TERM Meaning Unstability: increase with time of the ΔV applied to the reactor Strategy Search for stable materials Compromise between stability and activity University of Milan, Department of Physical Chemistry & Electrochemistry

STABILITY PERFORMANCE J. Divisek et al. , Int. J. Hydrogen Energy 15 (1990) 105

STABILITY PERFORMANCE J. Divisek et al. , Int. J. Hydrogen Energy 15 (1990) 105 University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Hetrogeneous Catalysis at Electrodes University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Hetrogeneous Catalysis at Electrodes University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS General Variation of electrode reaction rate at constant potential Specific Effect of electrode

ELECTROCATALYSIS General Variation of electrode reaction rate at constant potential Specific Effect of electrode material on the electrode reactin rate University of Milan, Department of Physical Chemistry & Electrochemistry

ELETTROCATALYSIS Search for new materials and/or new operating conditions in order to Improve :

ELETTROCATALYSIS Search for new materials and/or new operating conditions in order to Improve : activity efficiency selectivity Reduce : investment costs operational costs Increase : life time Avoid : pollution University of Milan, Department of Physical Chemistry & Electrochemistry

Electrocatalysis ELECTRONIC FACTORS Primary vs. Secondary Effects Primary Effects Chemical interactions between electrode surface

Electrocatalysis ELECTRONIC FACTORS Primary vs. Secondary Effects Primary Effects Chemical interactions between electrode surface and reactants, intermediates and/or products Secondary Effects Non-specific interactions between electrode surface and reactants, intermediates and/or products University of Milan, Department of Physical Chemistry & Electrochemistry

Generalized Kinetic Equation University of Milan, Department of Physical Chemistry & Electrochemistry

Generalized Kinetic Equation University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Primary Effects University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Primary Effects University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Hydrogen Evolution on Metal Electrodes University of Milan, Department of Physical Chemistry &

ELECTROCATALYSIS Hydrogen Evolution on Metal Electrodes University of Milan, Department of Physical Chemistry & Electrochemistry

BASIC CONCEPTS OF OXYGEN EVOLUTION ON OXIDE ELECTRODES MO + x. H 2 O

BASIC CONCEPTS OF OXYGEN EVOLUTION ON OXIDE ELECTRODES MO + x. H 2 O MO 1+x + 2 x. H+ + 2 xe (formation of higher oxide) MO 1+x MO + x/2 O 2 (higher oxide decomposition) University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Oxygen Evolution on Oxide Electrodes University of Milan, Department of Physical Chemistry &

ELECTROCATALYSIS Oxygen Evolution on Oxide Electrodes University of Milan, Department of Physical Chemistry & Electrochemistry

“Volcano” curves in CATALYSIS CO + 3 H 2 → CH 4 + H

“Volcano” curves in CATALYSIS CO + 3 H 2 → CH 4 + H 2 O University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Examples of Experimental Assessment University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Examples of Experimental Assessment University of Milan, Department of Physical Chemistry & Electrochemistry

Electrocatalytic Activity Relative Evaluation University of Milan, Department of Physical Chemistry & Electrochemistry

Electrocatalytic Activity Relative Evaluation University of Milan, Department of Physical Chemistry & Electrochemistry

ELETTROCATALYSIS Relative Assessment of Activity j DV 1 1 2 2 DV DV ln

ELETTROCATALYSIS Relative Assessment of Activity j DV 1 1 2 2 DV DV ln j DV 1 2 ln j University of Milan, Department of Physical Chemistry & Electrochemistry ln j

ELECTROCATALYSIS Electronic vs. Geometric Factors Electronic Factors Structure and chemical composition of materials Geometric

ELECTROCATALYSIS Electronic vs. Geometric Factors Electronic Factors Structure and chemical composition of materials Geometric Factors Surface area of materials (morphology) University of Milan, Department of Physical Chemistry & Electrochemistry

Real Surface Area Effect I. J. Brownand S. Sotiropoulos, J. Appl. Electrochem. , 30

Real Surface Area Effect I. J. Brownand S. Sotiropoulos, J. Appl. Electrochem. , 30 (2000) 107 University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Intensive vs. Extensive Quantities Independent of surface area extension Extensive Quantities Dependent on

ELECTROCATALYSIS Intensive vs. Extensive Quantities Independent of surface area extension Extensive Quantities Dependent on surface area extension University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Intensive Quantities Tafel slope Reaction mechanism Point of zero charge Surface chemistry University

ELECTROCATALYSIS Intensive Quantities Tafel slope Reaction mechanism Point of zero charge Surface chemistry University of Milan, Department of Physical Chemistry & Electrochemistry

MECHANICAL vs. CHEMICAL ACTIVATION h /V Ni-Raney sand blas smo oth ted N i

MECHANICAL vs. CHEMICAL ACTIVATION h /V Ni-Raney sand blas smo oth ted N i Ni Log (j/m. A cm-2) University of Milan, Department of Physical Chemistry & Electrochemistry

EFFECT OF SURFACE CRYSTALLOGRAPHIC ORIENTATION Ag University of Milan, Department of Physical Chemistry &

EFFECT OF SURFACE CRYSTALLOGRAPHIC ORIENTATION Ag University of Milan, Department of Physical Chemistry & Electrochemistry

EFFECT OF PARTICLE SIZE (110) particle size University of Milan, Department of Physical Chemistry

EFFECT OF PARTICLE SIZE (110) particle size University of Milan, Department of Physical Chemistry & Electrochemistry

EFFECT OF PREPARATION University of Milan, Department of Physical Chemistry & Electrochemistry

EFFECT OF PREPARATION University of Milan, Department of Physical Chemistry & Electrochemistry

Ir. O 2+Rh. Ox Mixed Oxides H 2 Evolution University of Milan, Department of

Ir. O 2+Rh. Ox Mixed Oxides H 2 Evolution University of Milan, Department of Physical Chemistry & Electrochemistry

Sn. O 2 + Ir. O 2 Mixed Oxides Cl 2 Evolution University of

Sn. O 2 + Ir. O 2 Mixed Oxides Cl 2 Evolution University of Milan, Department of Physical Chemistry & Electrochemistry

General Trends in Research Better dispersion Maximize surface area Specific technology Better mixing Synergetic

General Trends in Research Better dispersion Maximize surface area Specific technology Better mixing Synergetic effects Composite materials University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS University of Milan, Department of Physical Chemistry & Electrochemistry

ESSEE 4 4 th European Summer School ELECTROCHEMICAL ENGINEERING THE END Thank you for

ESSEE 4 4 th European Summer School ELECTROCHEMICAL ENGINEERING THE END Thank you for your attention University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Transition Metal Oxides: A Technological Breakthrough University of Milan, Department of Physical Chemistry

ELECTROCATALYSIS Transition Metal Oxides: A Technological Breakthrough University of Milan, Department of Physical Chemistry & Electrochemistry

University of Milan, Department of Physical Chemistry & Electrochemistry

University of Milan, Department of Physical Chemistry & Electrochemistry

BRINE ELECTROLYSIS Na. Cl + H 2 O + 2 e ½Cl 2 +

BRINE ELECTROLYSIS Na. Cl + H 2 O + 2 e ½Cl 2 + Na. OH + ½H 2 Anode: Graphite 2 Cl- Cl 2 + 2 e H 2 O ½O 2 + 2 H+ + 2 e Graphite is consumed University of Milan, Department of Physical Chemistry & Electrochemistry

GRAPHITE ANODES An Cat IR University of Milan, Department of Physical Chemistry & Electrochemistry

GRAPHITE ANODES An Cat IR University of Milan, Department of Physical Chemistry & Electrochemistry

DIMENSIONALLY STABLE ANODES DSA® Graphite replaced by insoluble materials H. Beer H. B. Beer.

DIMENSIONALLY STABLE ANODES DSA® Graphite replaced by insoluble materials H. Beer H. B. Beer. J. Electrochem. Soc. 127 (1980) 303 C S. Trasatti, Electrochim. Acta 45 (2000) 2377 University of Milan, Department of Physical Chemistry & Electrochemistry

DIMENSIONALLY STABLE ANODES (DSA®) Silver Jubilee celebrated in 1989 at the Spring Meeting of

DIMENSIONALLY STABLE ANODES (DSA®) Silver Jubilee celebrated in 1989 at the Spring Meeting of the Electrochemical Society, Los Angeles University of Milan, Department of Physical Chemistry & Electrochemistry

INDUSTRIAL PERFORMANCE University of Milan, Department of Physical Chemistry & Electrochemistry

INDUSTRIAL PERFORMANCE University of Milan, Department of Physical Chemistry & Electrochemistry

Chlor-Alkali Cells APPLIED VOLTAGE Breakdown Graphite DSA University of Milan, Department of Physical Chemistry

Chlor-Alkali Cells APPLIED VOLTAGE Breakdown Graphite DSA University of Milan, Department of Physical Chemistry & Electrochemistry

1971 - First Paper in the Open Literature University of Milan, Department of Physical

1971 - First Paper in the Open Literature University of Milan, Department of Physical Chemistry & Electrochemistry

TRANSITION METAL OXIDE ELECTRODES Applications Chlorine evolution Oxygen evolution Hydrogen evolution Electroorganic reactions p.

TRANSITION METAL OXIDE ELECTRODES Applications Chlorine evolution Oxygen evolution Hydrogen evolution Electroorganic reactions p. H sensors Supercapacitors Oxygen reduction CO 2 reduction Ozone electrosynthesis University of Milan, Department of Physical Chemistry & Electrochemistry

TRANSITION METAL OXIDES ü Dioxides (Ru. O 2, Ti. O 2) ü Spinels (Co

TRANSITION METAL OXIDES ü Dioxides (Ru. O 2, Ti. O 2) ü Spinels (Co 3 O 4) ü Perovskites (La. Ni. O 3) ü Pyrochlores (Bi 2 Ru 2 O 7) University of Milan, Department of Physical Chemistry & Electrochemistry

ACTIVATED ELECTRODES Active layer Support University of Milan, Department of Physical Chemistry & Electrochemistry

ACTIVATED ELECTRODES Active layer Support University of Milan, Department of Physical Chemistry & Electrochemistry

Morphology of Active Layers Effect of precursor and Calcination Temperature 300°C Ru. O 2

Morphology of Active Layers Effect of precursor and Calcination Temperature 300°C Ru. O 2 500°C Ru. Cl 3 • x H 2 O Ru(NO)(NO 3)3 • x H 2 O University of Milan, Department of Physical Chemistry & Electrochemistry

PROPERTIES OF ACTIVE LAYERS Techniques of Characterization ü XRD, SEM, TEM, AES, XPS, RBS,

PROPERTIES OF ACTIVE LAYERS Techniques of Characterization ü XRD, SEM, TEM, AES, XPS, RBS, IRS, SIMS, ICPES, NRA, Radiotracer ü Voltammetry, potential step, point of zero charge, impedance. Structure, morphology, surface area, stability, surface composition, acid-base behaviour University of Milan, Department of Physical Chemistry & Electrochemistry

Morphology of Active Layers Surface Charge total = outer + inner University of Milan,

Morphology of Active Layers Surface Charge total = outer + inner University of Milan, Department of Physical Chemistry & Electrochemistry

CYCLIC VOLTAMMETRY Electrochemical Spectrum University of Milan, Department of Physical Chemistry & Electrochemistry

CYCLIC VOLTAMMETRY Electrochemical Spectrum University of Milan, Department of Physical Chemistry & Electrochemistry

OXIDE ELECTRODES Surface charge and surface concentation of active sites MOx(OH)y + d. H+

OXIDE ELECTRODES Surface charge and surface concentation of active sites MOx(OH)y + d. H+ + de ↔ MOx-d(OH)y+d University of Milan, Department of Physical Chemistry & Electrochemistry

TRANSITION METAL OXIDE ELECTRODES Voltammetric analysis • Surface area • Morphology • Porosity •

TRANSITION METAL OXIDE ELECTRODES Voltammetric analysis • Surface area • Morphology • Porosity • Surface composition • Stability University of Milan, Department of Physical Chemistry & Electrochemistry

SURFACE CHARGE University of Milan, Department of Physical Chemistry & Electrochemistry

SURFACE CHARGE University of Milan, Department of Physical Chemistry & Electrochemistry

MIXED OXIDE ELECTRODES Surface Charge vs. Composition University of Milan, Department of Physical Chemistry

MIXED OXIDE ELECTRODES Surface Charge vs. Composition University of Milan, Department of Physical Chemistry & Electrochemistry

SURFACE SEGREGATION IN MIXED OXIDES Ru. O 2+Ir. O 2 (Ir) Co 3 O

SURFACE SEGREGATION IN MIXED OXIDES Ru. O 2+Ir. O 2 (Ir) Co 3 O 4+Ru. O 2 (Ru) Ir. O 2+Sn. O 2 (Ir) Ru. O 2+Zr. O 2 (Zr) Ir. O 2+Ta 2 O 5 (Ta) Ru. O 2+Ti. O 2 (Ti) Ru. O 2+Pt. Ox (Pt) Ni. Ox+Fe. Ox (Ni) Ni. Ox+Co 3 O 4 (Ni) Rh. Ox+Ru. O 2 (Rh) University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCHEMICAL SURFACE ANALYSIS University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCHEMICAL SURFACE ANALYSIS University of Milan, Department of Physical Chemistry & Electrochemistry

SURFACE vs. BULK COMPOSITION University of Milan, Department of Physical Chemistry & Electrochemistry

SURFACE vs. BULK COMPOSITION University of Milan, Department of Physical Chemistry & Electrochemistry

Normalization to Unit Real Surface Area University of Milan, Department of Physical Chemistry &

Normalization to Unit Real Surface Area University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTRODE STABILITY TEST University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTRODE STABILITY TEST University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Oxide Electrodes: Redox Relais University of Milan, Department of Physical Chemistry & Electrochemistry

ELECTROCATALYSIS Oxide Electrodes: Redox Relais University of Milan, Department of Physical Chemistry & Electrochemistry