Ultrastable Photoelectrodes for Solar Water Splitting Based on

Subscriber access provided by UNIV OF DURHAM

Energy, Environmental, and Catalysis Applications

Ultra-Stable Photoelectrodes for Solar Water Splitting Based on Organic Metal Halide Perovskite Fabricated by Lift-Off Process Seongsik Nam, Cuc Thi Kim Mai, and Ilwhan Oh ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b00686 • Publication Date (Web): 11 Apr 2018 Downloaded from http://pubs.acs.org on April 11, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Ultra-Stable Photoelectrodes for Solar Water Splitting Based on Organic Metal Halide Perovskite Fabricated by Lift-Off Process SeongSik Nam ┴, Cuc Thi Kim Mai┴ and Ilwhan Oh, †,┴,∗ †

Department of Applied Chemistry and ┴Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, 730-701, Republic of Korea

Keywords: Perovskite, water photolysis, photocathode, solar energy, photoelectrochemistry

ACS Paragon Plus Environment

1

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 21

Abstract

Herein we report on integrated photoelectrolysis of water employing organic metal halide (OMH) perovskite material. As generic OMH perovskite material and device architecture are highly susceptible to degradation by aqueous electrolytes, we have developed a versatile mold-cast and lift-off process to fabricate and assemble multi-purpose metal encapsulation onto perovskite devices. With the metal encapsulation effectively protecting the perovskite cell and also functioning as electrocatalyst, the high-performance perovskite photoelectrodes exhibit high photovoltage and the photocurrent that are effectively inherited from the original solid-state solar cell. More importantly, thus-fabricated perovskite photoelectrode demonstrates record-long unprecedented stability even at highly oxidizing potential in strong alkaline electrolyte. We expect that this versatile lift-off process can be adapted in a wide variety of photoelectrochemical devices to protect the material surfaces from corroding electrolyte and facilitate various electrochemical reactions.


2

Page 3 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Introduction

2

The 2015 Paris Climate Conference witnessed leaders and scientists around the world reaching

3

consensus that carbon emission by mankind has caused global warming and concerted efforts are

4

needed to replace the traditional fossil fuel-based energy system with renewable ones.1 For the

5

last decade, the cost of solar energy has reduced dramatically and, in some regions with higher

6

solar irradiance, has already gone below the retail electricity cost (grid parity).2 On the other

7

hand, intermittent nature of solar energy – electricity can be produced only during daytime –

8

requires development of energy storage system (ESS), which can store excess solar energy.

9

Recently, organic metal halides (OMH) perovskites have emerged as promising new material

10

for solar energy conversion3–8. With a generic chemical formula of CH3NH3PbI3 (MAPbI3), this

11

material shows strong light absorption and excellent charge carrier diffusion length in spite that

12

this material is synthesized at low temperature through simple low-cost processes. Even though

13

the current worldwide research activities on OMH perovskites are mostly focused on

14

photovoltaics, solar water splitting is another relevant field that might benefit from the emerging

15

OMH perovskite materials.9 Due to the intermittent nature of solar energy, storing solar energy

16

in chemical fuels is necessary to compliment photovoltaics.

17

Early reports on perovskite-based solar water splitting can be categorized into the

18

photovoltaic-electrolyzer configuration, where perovskite solar cells are separated from the fuel-

19

generating electrolyzer10,11 On the other hand, the integrated photoelectrolysis is an alternative

20

configuration, which involves intimate contact between the photoelectrode and electrolyte with

21

the merits of simplified wiring and saved space.12. In 2015, Da et al. first reported that perovskite

22

cells can be directly immersed in electrolyte and electrolysis can be performed at least for a short

23

period of time.13 However, in order to realize unassisted H2 generation, a sacrificial agent


3


Page 4 of 21

1

(sulfide) had to be utilized.

Recently, Hoang et al. introduced a pinhole-free and carbon

2

nanotube/polymer composite protection layer and extended the operational stability to ~30 min.14

3

Most recently, Crespo-Quesada et al. reported another breakthrough in which a simple

4

encapsulation using low-melting-point Field’s metal to protect the H2-generating perovskite

5

photocathode and demonstrated that the photocathode can operate for as long as 2 hours in a

6

mild neutral electrolyte before degradation.15 Overall, although pioneering studies have been

7

reported on solar water splitting on photoelectrodes based on OMH perovskites, integrated

8

photoelectrolysis of water employing perovskite photoelectrodes is yet to be further investigated,

9

especially with respect to materials and device stability.

10

Here in this report, we report on a versatile mold-cast and lift-off process to introduce a metal

11

encapsulation/catalyst layer upon the perovskite device structure to fabricate an ultra-stable

12

photoelectrode for solar water splitting. The metal encapsulation layer is composed of low

13

melting point eutectic Field’s metal (FM) and additional electrodeposited Ni catalyst layer for

14

water oxidation. We demonstrate that the photoelectrode fabricated through the lift-off process

15

can operate in harsh oxidative environment for >10 hours, a lifetime that is one order of

16

magnitude higher than previous reports. Furthermore, while previous studies on perovskite-

17

based solar water splitting were limited to a mild medium (neutral pH) due to the perovskite

18

stability, our ultra-stable perovskite photoelectrode can effectively operate in strong alkaline

19

electrolyte, a merit that will reduce overpotential and increase system efficiency. We believe that

20

the perovskite devices fabricated by the versatile lift-off can be used in a number of different

21

applications, such as carbon dioxide reduction to generate useful products.

22 23

Results and Discussion


4

Page 5 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

We fabricated photoelectrodes from solid-state OMH perovskite solar cells and

2

performed photoelectrochemical measurements. Figure 1a shows a schematic of the

3

photoelectrolysis cell employed in this work, which is composed of perovskite

4

photoelectrode directly in contact with liquid electrolyte (integrated photoelectrolysis), a

5

Pt counter electrode, and a reference electrode. Simulated sunlight is shining upon the

6

glass window face of the perovskite photoelectrode. The perovskite device has an n-i-p

7

heterojunction structure, which is the most wildly adapted structure of various device

8

configurations of perovskite solar cells, and has been fabricated according to the

9

previously published procedures.14 Figure 1b shows a cross-sectional SEM image of the

10

solid-state n-i-p solar cell, which shows smooth layers and clear interfaces of composing

11

thin films. The perovskite solar cell is composed of n-type compact/mesoporous TiO2 as

12

electron transport layer (ETL), methylammonium lead iodide (CH3NH3PbI3) perovskite

13

light absorber, p-type spiro-MeOTAD as hole transport layer (HTL), and final Au layer as

14

metal contact.

15

(~200nm) to facilitate the following metal encapsulation process.

16

photoanode fabricated from the n-i-p solar cells, photo-generated holes will migrate

17

toward the electrolyte and induce oxidation reaction (oxygen evolution). Compared with

18

the perovskite photocathode, which conducts reduction reaction (hydrogen evolution), the

19

photoanode should endure significantly more harsh corroding environment. Thus

20

previous studies on photoanode has been limited to metal oxide semiconductors.16 Figure

21

1c shows an XRD spectrum of the perovskite solar cell, which shows sharp diffraction

22

peaks corresponding to the (110), (220), and (310) lattice planes and confirm the

23

formation of tetragonal crystal structure of MAPbI3 in accordance with literature. Prior to

Note that the thickness of the Au layer was intentionally set thicker In the perovskite


5


Page 6 of 21

1

fabrication of photoelectrode, the performance of the solid-state perovskite cells were

2

measured.

3

perovskite solar cell, which shows decent performance metrics. (open-circuit potential of

4

0.98V, short-circuit current of 21mA/cm2, fill factor of 0.78, and power conversion

5

efficiency of 15.6%)

Figure 1d shows a representative current-voltage (I-V) graph for the

6 7

Figure 1. (a) Schematic illustration of integrated photoelectrolysis cell with perovskite

8

photoelectrode. (b) SEM cross-sectional image of the perovskite device employed. (c) X-ray

9

diffraction spectrum for the perovskite film formed on porous TiO2/FTO glass substrate. (d) J−V

10

curve for the solid-state perovskite cell under standard AM1.5 illumination (100 mW/cm2).

11

Upon the finished solid-state perovskite cells, a metal encapsulation was laid by a lift-

12

off process, as shown in Figure 2. (For fabrication details, see Experimental section.)


6

Page 7 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Briefly, onto a flat substrate was attached a mold structure with appropriate dimension

2

and shape to form metal encapsulation. Onto the mold structure, weighed amount of

3

Field’s metal (FM) was added and heated to ~70°C to mold cast metal encapsulation.

4

(Field’s metal is a eutectic alloy of Bi, Sn, and In with low melting point of 62°C) After

5

cooling down to room temperature, a FM disc was formed which contained a smooth

6

mirror-like surface. (See Figure S-1) As the FM itself is not an active catalyst toward

7

water oxidation, additional catalyst layer was deposited onto the FM disc. For this

8

purpose, Ni was electrodeposited because it is a low-cost non-precious metal catalyst for

9

water oxidation. (See Figure S-2) Furthermore, we found that the thin Ni film can

10

effectively protect the underlying FM in harsh alkaline and oxidative environment. The

11

Ni thin film was electrodeposited in a nickel sulfamate bath by applying a constant

12

current. (See Figure S-2) The optimum thickness of the Ni catalyst layer was found to be

13

~10µm. Thinner film tends to expose the underlying FM, which results in corrosion of

14

the FM in electrolyte, whereas thicker film tends to possess substantial lateral stress,

15

bending the underlying FM. Then the Ni/FM disc was removed off the mold. The Ni/FM

16

metal disc was placed upon the solid-state perovskite solar cell and was bonded to the

17

underlying Au layer by briefly annealing at 70°C in an inert atmosphere to establish

18

electric contact between the Ni/FM and the underlying Au electrode. Finally, the whole

19

bonded device was encapsulated by epoxy sealant excluding the active electrode area and

20

the optical aperture. Compared to previously reported manual application of Field’s metal,

21

we found that our mold casting and lift off process possesses several merits: this process

22

allows us to precisely define diameter and thickness of the metal encapsulation and to

23

fabricate a very smooth electrode surface, which is important for the following processes.


7


Page 8 of 21

1

In addition, additional functional layers (Ni thin film in this work) can be easily deposited.

2

Finally, in the critical process of bonding between the FM and the perovskite device, only

3

a brief annealing is enough to form a good bonding, which minimizes damages to the

4

underlying perovskite device. Figure 2b shows photographs of the actual photoelectrode

5

that was fabricated through the lift-off process described above. The left image shows the

6

Ni/FM encapsulation face (active electrode area), which will be in direct contact with

7

electrolyte, while the right image shows the glass window face, though which incident

8

light passes.

9 10

Figure 2. (a) Schematic illustration of lift-off process to fabricate metal-encapsulated perovskite

11

photoelectrode. (b) Photographic image of completed photoelectrode.

12

Performance of the metal-encapsulated perovskite photoelectrode was examined in

13

integrated photoelectrolysis in three-electrode configuration as shown in Figure 1a. The

14

perovskite photoelectrode was immersed in electrolyte and simulated sunlight was


8

Page 9 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

irradiated upon the glass face of the photoelectrode, while water splitting reaction

2

proceeds on the Ni/FM electrode face. In the J-V graph for the oxygen evolution reaction

3

in neutral solution, the perovskite photoelectrode generates a substantial photocurrent (red

4

line), which correspond to light-driven water oxidation to O2. The photographic image in

5

Figure 3c shows oxygen gas evolving from the active area of the perovskite

6

photoelectrode. As control experiment, the dotted black line in Figure 3a corresponds to

7

the response of the perovskite photoelectrode with Ni catalyst in dark and exhibits

8

virtually no current, indicating that most of the current at the irradiated photoelectrode is

9

actual photocurrent. As a reference, response from a Ni metal electrode (no perovskite

10

cell) was measured (blue line). A shoulder peak at 1.6V was noted, which corresponds to

11

oxidation of Ni to form nickel oxide. It is well known that nickel oxide can function as an

12

active catalyst for oxygen evolution reaction (OER).17 With respect to E°’(O2/H2O), the

13

formal potential of OER at pH 9.2, a large overpotential was observed with the onset of

14

OER located at 1.2V, which reflected a slow electrode kinetics in near-neutral electrolyte.

15

The potential difference between the perovskite photoelectrode (red line) and the metallic

16

Ni electrode (blue line) is the photovoltage obtained by the perovskite photoelectrode

17

(~1.0V), which means that the photovoltage of the solid-state perovskite cell is well

18

transferred to the photoelectrode. It should be noted that the EVB (valence-band edge

19

energy) of MAPbI3 is higher than E°(O2/H2O) and, if the perovskite layer is in direct

20

contact with electrolyte, the photogenerated holes from the perovskite will not be able to

21

drive water oxidation reaction. However, in our perovskite device, additional HTL and

22

metal layers exist between the perovskite layer and the electrolyte thus the

23

aforementioned energetic requirement for water splitting does not apply anymore. The


9


Page 10 of 21

1

photocurrent of the perovskite photoelectrode became saturated at positive potential

2

region, which is mainly limited by the incident light intensity. It should be noted that the

3

light intensity on the photoelectrode surface is attenuated to 0.7sun due to the absorption

4

by reflector and electrolyte. Assuming a linear relationship between photocurrent and

5

light intensity, the saturation current of 16mA/cm2 at 0.7sun in Fig. 3 matches well with

6

the short-circuit current of 21mA/cm2 at 1sun in Fig.1(d).

7

Previous reports on integrated perovskite photoelectrolysis has been performed mainly

8

in near-neutral electrolytes, because the solid-state perovskite cell and even the protective

9

layer can be easily corroded in strong acid or alkaline solutions.14 However, electrolysis

10

or photoelectrolysis under bulk near-neutral pH conditions is inefficient. In near-neutral

11

pH, severe pH gradient near electrode surfaces and electrode kinetics are slower than in

12

acidic or alkaline conditions. Furthermore, potentially explosive, stoichiometric mixtures

13

of H2 and O2 can be produced over active catalysts for recombination of products.18,19

14

Thus, photoelectrolysis should be done in acid or alkaline condition. For this reason, we

15

tested our metal-encapsulated perovskite photoelectrode in strong alkaline solution (pH

16

14) as shown in Figure 3b. As expected from faster electrode kinetics and smaller pH

17

gradient in alkaline condition, the current rises much faster in alkaline solution; the

18

overpotential at 10mA/cm2 is measured to be 0.915 V at pH 9.2 as compared to 0.519 V

19

at pH 14. Also note that now the Ni oxidation peak more significant, indicating formation

20

of thicker nickel oxide film on surface at high pH.


10

Page 11 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1 2

Figure 3. (a) Voltammogram of perovskite photoanode with 10µm Ni catalyst under

3

simulated illumination (0.7 sun; red curve), under dark (dashed curve), and on metallic Ni

4

electrode (blue curve) as reference.

5

Voltammogram of perovskite photoanode with 10µm Ni catalyst under simulated

6

illumination (0.7 sun; red curve), under dark (dashed curve), and on metallic Ni electrode

7

(blue curve) as reference. Electrolyte was 1.0M KOH solution (pH 14). (c) Photographic

8

image of photoanode surface with oxygen bubbles emerging from the active area.

9

(diameter ~6 mm).

Electrolyte was K-Borate solution (pH 9.2). (b)


11


Page 12 of 21

1

In order to assess the long-term stability and reliability of the metal-encapsulated

2

perovskite photoelectrode toward solar water splitting, long-term performance of the

3

photoelectrode was measured. Previous reports indicate that typical perovskite devices

4

are prone to performance degradation due to moisture and water and loses most activity

5

within a few minutes.13 Figure 4 shows the long-term response from the perovskite

6

photoelectrode measured at constant potential. Initially, a slight decrease in current was

7

observed, which probably occurred because oxygen bubbles generated covered the

8

surface and reduced the active area of the photoelectrode.

9

encapsulated perovskite exhibited a highly stable response in a prolonged operation for

Afterwards, the metal-

10

several hours.

Quantitatively, the perovskite photoelectrode maintained 93 % of the

11

initial stabilized current after 5 hours. This duration of continued operation demonstrates

12

an unprecedented record-long stability for integrated photoelectrolysis based on

13

perovskite.

14

photoelectrode showed a catastrophic degradation in photocurrent.

15

understand the sudden decrease in performance, the photovoltaic response was measured

16

after the long-term operation.

17

catastrophic degradation of the perovskite photoelectrode shows that the photovoltaic

18

performance of the perovskite solar cell has been severely degraded. We note that the

19

Ni/FM electrode itself shows a quite stable response for much longer time scale. Thus we

20

assume that the long-term degradation of the perovskite photoelectrode comes mainly

21

from the perovskite photovoltaic layers rather than from the Ni/FM encapsulation. There

22

can be two possible reasons for this long-term degradation of the perovskite layers. First,

23

it is well known from the literature20 that especially in the presence of electric field and

However, after ca. 6 hours of continuous operation, the perovskite In order to

As shown in in Fig. S-5, the I-V curve after the


12

Page 13 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

water, the perovskite material is susceptible to degradation to PbI2. Even though our

2

perovskite photoelectrodes have been sealed as completely as possible, some pinholes

3

might exist through which water can leak slowly.

4

adhesion between the FM and the underlying Au is quite strong, the adhesion between the

5

Au and the underlying HTL layers is relatively weak. If some part of the Au layer

6

becomes detached from the HTL, that can also lead to the sudden decrease in

7

performance.

Second, we found that while the

8

9 10

Figure 4. Current vs time graph of perovskite photoanode under illumination (0.7 sun)

11

and bias (1.3 V vs RHE) in KOH solution (pH 14).

12


13


Page 14 of 21

1

Conclusions

2

In conclusion, we have successfully developed a versatile lift-off process to fabricate

3

metal-encapsulated perovskite photoelectrodes. The lift-off process allows us to mold

4

cast the encapsulation alloy in precise dimensions and to deposit additional functional

5

layers with catalytic and protective functions. When combined with high-performance

6

perovskite solar cells, the metal-encapsulated perovskite photoelectrode exhibits high

7

photovoltage and photocurrent responses toward water oxidation. Furthermore, excellent

8

long-term stability of the perovskite photoelectrode was demonstrated in strongly

9

oxidizing environment and harsh electrolyte.

Previously, even the perovskite

10

photoelectrodes with protective layers were able to operate only in near-neutral pH for a

11

limited period of duration. We expect that this versatile lift-off process can be adapted in

12

a wide variety of photoelectrochemical devices (e.g. Si solar cells or tandem devices) to

13

protect the material surfaces from corroding electrolyte and facilitate various

14

electrochemical reactions (e.g. CO2 reduction)

15 16

Experimental Section

17

Fabrication of perovskite photoelectrodes. For details of fabrication process for solid-

18

state perovskite solar cells, refer to our previous report.14 To form metal encapsulation, a

19

plastic mold with a hole (diameter ~6mm) was attached to a fluorine-doped tin oxide

20

(FTO) coated glass (Pilkington). The thickness of the plastic mold was 2.5mm. Due to

21

high viscosity of FM, we found that it is difficult to form a thinner FM layer. After

22

placing the mold on a hot plate at 70°C in ambient air, the mold was filled with 0.46g

23

Field's metal (Bi-In-Sn Ingot, Alfa Aesar). After the Field’s metal melted completely, top


14

Page 15 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

surface was covered with a slide glass to form a flat and smooth surface and the mold was

2

cooled down. Ni was electrodeposited from a sulfamate solution that consisted of 325 g

3

L-1 Ni(II) sulfamate and 30 g L-1 H3BO3 with the pH adjusted to ~4.0 using KOH.21,22

4

Electrodeposition was performed by applying a cathodic current of 20 mA/cm2 using a

5

potentiostat (FR/SR 150, BioLogic) in a two-electrode configuration with a Pt mesh

6

counter electrode. Then the Ni/FM disc was removed off the mold. The Ni/FM metal disc

7

was placed upon the solid-state perovskite solar cell and was bonded to the underlying Au

8

layer by briefly annealing at 70°C in an inert atmosphere to establish electric contact

9

between the Ni/FM and the underlying Au electrode. Then an optical aperture (6 mm

10

diameter), the area of which is identical with that of the FM disc, was attached on the

11

glass window face. For electrical connection, two wires were soldered to the two Au

12

electrodes. Finally, the whole photoelectrode assembly was sealed completely with an

13

epoxy sealant (EA 9460, LOCTITE) except the active area (~0.28cm2) and was dried for

14

12 hours.

15

Measurements and Characterization. XRD measurement of perovskite thin film was

16

conducted by a model SWXD(X-MAX/2000-PC) x-ray diffraction instrument. Electron

17

microscope images were obtained by a JEOL model JSM-6701F scanning electron

18

microscope (SEM). The current–voltage (J-V) curves were measured using a potentiostat

19

(model SP 150, BioLogic) under simulated AM 1.5 sunlight at 100mWcm-2 irradiance

20

generated by an 150W solar simulator (model 71581, Newport) with the intensity

21

calibrated with a certified Si reference cell. The fabricated perovskite photoanode was

22

adopted in a Teflon cell with a Pt mesh counter electrode and a saturated calomel

23

electrode (SCE) as reference electrode. The electrolytes were the K-Borate (1M boric acid


15


Page 16 of 21

1

+ 0.5M KOH in distilled water – pH 9.2) or 1M KOH solution without purge with inner

2

gas. The vertical light from the solar simulator was reflected by a 45-degree full reflector

3

(Oriel) and was introduced into the photoelectrochemical cell through a quartz window

4

and the electrolyte (path length ~2cm), resulting in an attenuated light intensity of 0.7sun

5

on the face of the immersed photoelectrode.

6 7 8

Supporting Information. SEM images and EDS spectra for both bare FM and Ni/FM surfaces.

9

Voltage-time graph for Ni electrodeposition.

10 11

AUTHOR INFORMATION

12

Corresponding Author

13

*E-mail: [email protected] (I.O.)

14 15

Notes

16

The authors declare no competing financial interest.

17 18

ACKNOWLEDGMENT

19

I.O. acknowledges the support from the National Research Foundation (NRF) of Korea (NRF-

20

2016R1A2B4011046); Ministry of Science and ICT (MSIT), Korea, Information Technology Research


16

Page 17 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Center (ITRC), Institute for Information & Communications Technology Promotion (IITP) (IITP-2017-

2

2014-0-00639).

3 4


17


Page 18 of 21

1 2 3

References

4

(1)

United nations conference on climate change http://www.cop21.gouv.fr/en/.

5

(2)

Handbook of Photovoltaic Science and Engineering; John Wiley & Sons, Ltd, 2011.

6

(3)

Green, M. A.; Ho-Baillie, A.; Snaith, H. J. The Emergence of Perovskite Solar Cells. Nat. Photonics 2014, 8, 506.

7 8

(4)

We Do Not Know? J. Phys. Chem. Lett. 2015, 6 (2), 279–282.

9 10

Egger, D. A.; Edri, E.; Cahen, D.; Hodes, G. Perovskite Solar Cells: Do We Know What

(5)

Huang, J.; Shao, Y.; Dong, Q. Organometal Trihalide Perovskite Single Crystals: A Next

11

Wave of Materials for 25% Efficiency Photovoltaics and Applications Beyond? J. Phys.

12

Chem. Lett. 2015, 6 (16), 3218–3227.

13

(6)

Solar Cells. J. Phys. Chem. Lett. 2014, 5 (23), 4175–4186.

14 15

(7)

18

Kim, H.-S.; Im, S. H.; Park, N.-G. Organolead Halide Perovskite: New Horizons in Solar Cell Research. J. Phys. Chem. C 2014, 118 (11), 5615–5625.

16 17

Zhao, Y.; Zhu, K. Solution Chemistry Engineering toward High-Efficiency Perovskite

(8)

Park, N.-G. Organometal Perovskite Light Absorbers Toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell. J. Phys. Chem. Lett. 2013, 4 (15), 2423–2429.


18

Page 19 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1


(9)

Park, S.; Chang, W. J.; Lee, C. W.; Park, S.; Ahn, H.-Y.; Nam, K. T. Photocatalytic

2

Hydrogen Generation from Hydriodic Acid Using Methylammonium Lead Iodide in

3

Dynamic Equilibrium with Aqueous Solution. Nat. Energy 2016, 2, 16185.

4

(10)

Luo, J.; Im, J.-H.; Mayer, M. T.; Schreier, M.; Nazeeruddin, M. K.; Park, N.-G.; Tilley, S.

5

D.; Fan, H. J.; Grätzel, M. Water Photolysis at 12.3% Efficiency via Perovskite

6

Photovoltaics and Earth-Abundant Catalysts. Science (80-. ). 2014, 345 (6204), 1593 LP-

7

1596.

8

(11)

BiVO4 Tandem Assembly for Photolytic Solar Fuels Production. J. Am. Chem. Soc. 2015,

9 10 11

Chen, Y.-S.; Manser, J. S.; Kamat, P. V. All Solution-Processed Lead Halide Perovskite-

137 (2), 974–981. (12)

Huang, Z.; Xiang, C.; Lewerenz, H.-J.; Lewis, N. S. Two Stories from the ISACS 12

12

Conference: Solar-Fuel Devices and Catalyst Identification. Energy Environ. Sci. 2014, 7

13

(4), 1207–1211.

14

(13)

Photoanode Enabled by Ni Passivation and Catalysis. Nano Lett. 2015, 15 (5), 3452–3457.

15 16

Da, P.; Cha, M.; Sun, L.; Wu, Y.; Wang, Z.-S.; Zheng, G. High-Performance Perovskite

(14)

Hoang, M. T.; Pham, N. D.; Han, J. H.; Gardner, J. M.; Oh, I. Integrated Photoelectrolysis

17

of Water Implemented on Organic Metal Halide Perovskite Photoelectrode. ACS Appl.

18

Mater. Interfaces 2016, 8 (19), 11904–11909.

19

(15)

Crespo-Quesada, M.; Pazos-Outón, L. M.; Warnan, J.; Kuehnel, M. F.; Friend, R. H.;

20

Reisner, E. Metal-Encapsulated Organolead Halide Perovskite Photocathode for Solar-

21

Driven Hydrogen Evolution in Water. Nat. Commun. 2016, 7, 12555.


19


1

(16)

Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q.; Santori, E. A.;

2

Lewis, N. S. Solar Water Splitting Cells. Chem. Rev. (Washington, DC, United States)

3

2010, 110 (11), 6446–6473.

4

(17)

Kenney, M. J.; Gong, M.; Li, Y.; Wu, J. Z.; Feng, J.; Lanza, M.; Dai, H. High-

5

Performance Silicon Photoanodes Passivated with Ultrathin Nickel Films for Water

6

Oxidation. Science (80-. ). 2013, 342 (6160), 836 LP-840.

7

(18)

Jin, J.; Walczak, K.; Singh, M. R.; Karp, C.; Lewis, N. S.; Xiang, C. An Experimental and

8

Modeling/simulation-Based Evaluation of the Efficiency and Operational Performance

9

Characteristics of an Integrated, Membrane-Free, Neutral pH Solar-Driven WaterSplitting System. Energy Environ. Sci. 2014, 7 (10), 3371–3380.

10 11

(19)

12 13

Nathan S. Lewis. Research Opportunities to Advance Solar Energy Utilization. 2016, 351 (6271).

(20)

Leijtens, T.; Eperon, G. E.; Noel, N. K.; Habisreutinger, S. N.; Petrozza, A.; Snaith, H. J. Stability of Metal Halide Perovskite Solar Cells. 2015, 1–23.

14 15

Page 20 of 21

(21)

McKone, J. R.; Warren, E. L.; Bierman, M. J.; Boettcher, S. W.; Brunschwig, B. S.;

16

Lewis, N. S.; Gray, H. B. Evaluation of Pt, Ni, and Ni-Mo Electrocatalysts for Hydrogen

17

Evolution on Crystalline Si Electrodes. Energy Environ. Sci. 2011, 4 (9), 3573–3583.

18

(22)

Tsuru, Y.; Nomura, M.; Foulkes, F. R. Effects of Boric Acid on Hydrogen Evolution and

19

Internal Stress in Films Deposited from a Nickel Sulfamate Bath. J. Appl. Electrochem.

20

2002, 32 (6), 629–634.

21


20

Page 21 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1


TOC graphic

2

3 4


21

Ultrastable Photoelectrodes for Solar Water Splitting Based on

Recommend Documents