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Electrocatalytic water splitting – an example of Ni

(OH)2/ Fe oxide hybrid electrode

Debajeet K. BORA, Laboratory for High Performance CeramicsEMPA Dübendorf, CH - 8600

Lab Seminar, LHPC, EMPA, 16.12.2014

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Catalysis

The term ‘‘catalysis’’ was coined in 1835 by the Swedish chemist Berzelius, but a suitable definition was introduced only many years later by Ostwald who wrote in 1894: ‘‘Catalysis is the acceleration of a slow chemical process by the presence of a foreign material’’. -G. Ertl, Angew. Chem., Int. Ed., 2009, 48, 6600–6606

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Basic Principles• catalysts enhance reaction rates by lowering the activation energy

• Opening of a new reaction pathway with lower activation energy

• Supply of partial bond for stabilizing the transition state and creating a balance of

energy required for breaking and making of reactant and products chemical

bonding

• Structure and redistribution of electronic configuration in synergy with reaction

pathway helps in mimizing the enygy barrier with lowering of activation eenrgy

• Its binding to the Substrate plays a role as adsorption and desorprtion are equally

important

• Electrocatalysis can promote a redox reaction in complicated mechanistic way with

the helps of electrochemical potenial grandient

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• Hydrogen based renewable energy sources getting momentum with the advent of OER , HER, ORR electrocatalysts

• Synergy between, substrate, reactant, intermediates and products plays an eminet role in making the process efficient

• design of active materials is an important aspect of electrocatalysis, their stability during the course of a reaction is a concern for nearly all electrodes used in energy conversion and storage system

• it is possible to monitor in situ the dissolution of catalysts atoms operando

• stability of catalyst is closely linked to an atomic- and molecular-level understanding of the catalytic mechanisms for water splitting reaction

• notably, perovskites based electrocatalysts for OER in alkaline conditions works very well from stability perspectives

NATURE MATERIALS | VOL 12 | FEBRUARY 2013 |

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Electrocatalysis

J. Am. Chem. Soc., 2011, 133 (36), pp 14431–14442

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-150

-100

-50

0

50

100

150

200

250

Cur

rent

Den

sity

[ A

/ cm

2 ]

Applied Potential vs. Ag/ AgCl [mV]

LB films with 40 dipping cycles

10 20 30 40 50 60 70 80 90 100 110 120

0.00003

0.00006

0.00009

0.00012

0.00015

0.00018

0.00021

Am

ount

of e

volv

ed O

2 (m

ol)

Time (min)

40 cycles LB films

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Metal oxide electrocataylsts for OER

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Metal oxide electrocataylsts for HER

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Different types of Electrocatalsyts

Electrocatalsyst

Overpotential

Current Density

References

Eelectrolyte and pH

Cubane like Calcium Mn Cluster, CaMn4O5

0.45 V or 1.68 V vs. RHE

10mA/cm2 JACS, 134, 2930, 2012

kOH, pH = 13

Co3O4 / N - graphene

0.4V or 1.63 vs. RHE

10mA/cm2 Nature Material, 10, 780 – 786, 2011

KOH, pH = 13

Non metal catalysts, N doped grpahite nanomaterials

0.38 V or 1.61 V vs. RHE

10mA/cm2 Nature Comm. DOI: 10.1038

KOH, pH = 13

N- doped carbon – NiOx catalysts

1.65 V vs. RHE

10mA/cm2 Do Do

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Electrocatalysts in PEC

J. Phys. Chem. C, 2012, 116 (8), pp 5082–5089

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SCIENCE sciencemag.org 26 SEPTEMBER 2014 • VOL 345

Electrocatalytic water splitting in tendem with perovskite solar cell

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SHINE project: to built an integrated nanoelectrolyzer based on this type of electrode