Operando Soft X ray Spectroscopy of

Nanoparticulate Hematite Film

Using UHV Electrochemical Flow Cell

Dr. Debajeet K. BORA, Laboratory for High Performance Ceramics

Empa. Swiss Federal Laboratories for Materials Science & Technology, 8600

Dubendorf, Switzerland

1

• Jinghua Guo , ALS, LBNL

• Artur Braun, Empa

• Per – Anders Glans, ALS, LBNL

• AXIS group members, ALS

• ALS support groups members, LBNL

• Dunwei Wang, Boston College

• Chun Du, Boston College

• Juan Valesco Valez, MSD, LBNL

LDRD: Soft X-Ray Spectroscopy for In-situ ElectronicStructure Study of Artificial Photosynthesis

Acknowledgements

2

Outline

• Motivation

• Introduction

• How the operando spectroscopy helps in finding the role of electron hole in PEC system – a brief overview

• Snapshots of in – situ advanced absorption chember – BL 6.3.1.2, ALS, LBNL

• First generation electrochemical flow cell

• How we can make a sustainable operando condition

Answer : Deisgn of new In-Situ Electrochemical Flow cell

• In-Situ XAS study on nanoparticulate n- type hematite film

deposited with Atomic Layer deposition

• O K and Fe L edge NEXAFS spectroscopy – hematite electronic structure during photoelectrochemical condition

• Conclusion 3

Motivation

• To study the electronic structure of nanoparticulate

hematite under artificial photosynthetic condition

• How we can employ electrochemistry inside the soft X ray

absorption chamber

• Focus is to built an in - situ electrochemical flow cell

which allows better control of chamber pressure with

good signal to noise ratio for the detector

• To increase the experimental feasibility for running higher

cycle of CV in order to have more informaiton during

operando condition

• To reproduce the two electronic transitions obtained in

earlier operando study with n- type hematite doped with

Si

• To relate soft x ray spectrosocpy results with charge

transfer chacracterisics4

.

h

h'

UnoccupiedMOs

OccupiedMOs

O 1s

Inte

nsi

ty (

a.u)

540535530525520515

Energy (eV)

XASXES

4a1

2b2

3a1

1b2

1b1

Soft X ray absorption spectroscopyPhotoelectrochemisty

SC- electrolyte interface Hematite Electronic structure

Introduction

5

How the operando spectroscopy helps in finding the role of

electron - hole in PEC system – a brief overview

6

First direct observation of molecular glance of watersplitting reaction

Artur Braun et. al., J. Phys. Chem. C, 2012, 116 (32), pp 16870–168757

Cell under illumination from solar simulator

8

Sequence of O1s NEXAFS spectra vs. V and h

Ref: Artur Braun et. al., J. Phys. Chem. C, 2012, 116 (32), pp 16870–16875 9

10

Snapshots of in – situ advanced absorption chember

(ISAAC) at BL 6.3.1.2, ALS, LBNL

First generation electrochemical flow cell

P. Jiang et. Al., Electrochem. Comm. 12, 820–822 (2010) 11

12

How we can make a sustainable operando condition?

Answer : Deisgn of new In-Situ Electrochemical Flow cell

Bora et. al., Rev. Sci. Instrum. 85, 043106 (2014)

Construction of the flow cell

13Bora et. al., Rev. Sci. Instrum. 85, 043106 (2014)

UHV testing of the flow cell

14Bora et. al., Rev. Sci. Instrum. 85, 043106 (2014)

15

Electrochemial experiment with theUHV flow cell

Bora et. al., Rev. Sci. Instrum. 85, 043106 (2014)