This slide describes about Hydrogen Evolution Reaction and effect of Cu substitution in enhancing the activity. Deconvolution of strain and ligand effect is explained in the slide and in the respective paper.

1. “Inverse Strain Effect in Atomic Scale” -
Enhanced Hydrogen Evolution Activity and
Durability in Cu substituted Palladseite
Saurav Chandra Sarma
14/11/2018
S.C. Sarma, V. Mishra, K.A. Ann Mary, S. Roy, S.C. Peter, ACS Energy Letters, (2018)
1

2. Introduction
Pd17Se15 (CuPd)17Se15
+Cu
Standard colloidal synthesis
Hydrogen has the highest energy
content per unit mass.
Feedstock for fuel cell
Ease of production from highly
abundant water
Why Hydrogen..?? Where does Cu
substitute in
Pd17Se15 lattice?
How does Cu
substitution affect
structure and
oxidation state?
What is the driving force for the
enhancement of the electrocatalytic activity?
2

3. Where does Cu substitute in Pd17Se15 lattice?
+Cu
3
Decrease in the
(330) plane
intensity with Cu
substitution
Left shift in the
PXRD peak
position instead
of right shift 
Inverse Strain
Effect
Cu
128 pm
Pd
163 pm
Se
190 pm

4. How does Cu Substitution affect Pd17Se15 lattice?
(0)
(-2)
XAFS experiment performed at P64 Beamline, PETRA III, DESY, Germany
4

5. Electrochemical Hydrogen Evolution Reaction (HER)
Onset improved
after Cu
substitution
High current
density at lower
overpotential
Pd17Se15
13.08 s-1 @200
mV
(CuPd)17Se15
126.3 s-1 @200
mV
5

6. Stability and Faradaic Efficiency Calculation
Time (mins)
6

7. Driving Force for Enhancement of Activity
Change in Surface Area
No significant
contribution from
surface area
7
Cdl α Surface Area

8. Substitution Effect
Ligand Effect:
Strain Effect:
Ensemble Effect:
Depends on the nature of the substituent
Depends on the size of the substituent
Depends on the coordination environment
How to
DECONVOLUTE
these effects..??
8

9. Deconvoluting Strain and Ligand Effect
a=b=c=8 Å a=b=c= 9 Å
a=b=c= 8 Å a=b=c= 9 Å
Ligand Effect Strain Effect
+Cu
 Constrained lattice parameter to A
 Cu- substituted
 Constrained lattice parameter to B
 No substitution
(CuPd)17Se15
(B)
Pd17Se15
(A)
Change in d-band center
= (d – Pd17Se15)
ɛavg=
𝐸𝜌 𝐸 𝑑𝐸
𝐸𝑓
−∞
𝜌 𝐸 𝑑𝐸
𝐸𝑓
−∞
9

10. Deconvoluting Strain, Ligand and Ensemble Effect
Selective-site blocking
10
• Pd2+ is not a good H2
adsorbing material.
• Se gets activated because of
tensile strain as well as Cu
leaching.

11. Conclusion
11
Effect of Cu
substitution
Stability for
30000 Cycles
Reason for
enhancement of
activity
Site of Cu
substitution
High TOF of
126.3 s-1.
Enhancement of
activity after Cu
substitution
Faradaic efficiency close to 100 %
was achieved.
Reason for expansion
of unit cell
H2O