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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
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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
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