M13 Virus-Incorporated Biotemplates on Electrode Surfaces To

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M13 Virus-Incorporated Biotemplates on Electrode Surfaces to Nucleate Metal Nanostructures by Electrodeposition Shanmugam Manivannan, Inhak Kang, Yeji Seo, Hyo-Eon Jin, Seung-Wuk Lee, and Kyuwon Kim ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b06545 • Publication Date (Web): 05 Sep 2017 Downloaded from http://pubs.acs.org on September 5, 2017

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ACS Applied Materials & Interfaces

M13 Virus-Incorporated Biotemplates on Electrode Surfaces to Nucleate Metal Nanostructures by Electrodeposition Shanmugam Manivannan[a], Inhak Kang[a],, Yeji Seo[a] , Hyo-Eon Jin[b,c], Seung-Wuk Lee[b] and Kyuwon Kim[a],* [a]

Electrochemistry Laboratory for Sensors & Energy (ELSE) Department of Chemistry, Incheon National University Incheon 406-772, Republic of Korea. [b] Department of Bioengineering, University of California, Berkeley, California 94720, USA [c] Present address: College of Pharmacy, Ajou University, Suwon 16499, Republic of Korea *E-mail: [email protected]

Abstract: We report a virus-incorporated biological template (biotemplate) on electrode surfaces and its use in electrochemical nucleation of metal nanocomposites as an electrocatalytic material for energy applications. The biotemplate was developed with M13 virus (M13) incorporated in silicate sol–gel matrix as a scaffold to nucleate Au–Pt alloy nanostructures by electrodeposition, together with reduced graphene oxide (rGO). The phage when engineered with Y3E peptides could nucleate Au–Pt alloy nanostructures, which ensured adequate packing density, simultaneous stabilization of rGO, and a significantly increased electrochemically active surface area. Investigation of the electrocatalytic activity of the resulting sol-gel composite catalyst toward methanol oxidation in an alkaline medium showed that this catalyst had greater mass activity than did the biotemplate containing wild-type M13, and than did monometallic Pt and other Au–Pt nanostructures with different compositions and supports. M13 in the nanocomposite materials provided a close contact between the Au–Pt alloy nanostructures and rGO. In addition, it facilitated the availability of an OH– -rich environment to the catalyst. As a result, efficient electron transfer and a synergistic catalytic effect of the Au and Pt in the alloy nanostructures toward methanol oxidation were observed. Our nanocomposite synthesis on the novel biotemplate and its application might be useful for developing novel clean and green energy-generating and energy-storage materials.

Keywords: Biotemplate, Electrodeposition, M13 virus, Au–Pt alloy, Methanol oxidation

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1.

Introduction Developing clean and green renewable energy sources is one of the most critical needs for

mankind. Direct methanol fuel cells (DMFCs) have attracted wide attention as power sources for portable electronic devices and fuel cell vehicles owing to their quick start-up, compactness and light weight, high power density, and simplicity.1-2 Moreover, DMFCs operating in alkaline media show advantageous features such as improved reaction kinetics, and a less corrosive environment for catalysts. DMFCs in alkaline media can also operate at relatively low potentials.2-5 However, wide application of the DMFC still requires addressing multiple issues including its high cost, low durability of its platinum (Pt) catalyst, and the relatively easy passage of methanol through membranes.5-7 In order to decrease the amount of Pt that needs to be loaded into DMFCs and to increase their efficiency levels, a secondary metal such as gold (Au),2 ruthenium (Ru),8-9 copper (Cu),10 and palladium (Pd)11 has been introduced. Pt-based bimetallic (alloy and core–shell) catalysts have been explored to develop DMFCs that operate in alkaline media, and represent an alternative way to minimize the amount of pure Pt-based catalyst loaded.2, 12-13 Furthermore, considerable efforts have been devoted to employing Au–Pt alloy nanostructures in order to take advantage of the synergistic effect between Au and Pt that had already been detemined.14-15 Reduced graphene oxide (rGO) is, due to its unique electronic and chemical properties arising from its 2D structure,16 a promising support for loaded metallic nanostructures in fuel cell applications2, 17-22, it is crucial to prevent its individual sheets from aggregating. In this regard, several approaches have been used to prevent aggregation between individual rGO sheets using biomolecules such as DNA,23 proteins24 and genetically modified viruses.25-27 And the resulting biomolecule-rGO composites have found significant applications in various biosensors28-30 and energy devices.31-32 In addition, substantial research is being pursued to develop rGO as support materials for metal nanostructures.12-13, 18 Such a combination can provide a highly active surface area, enhanced catalytic activity, and durability for long times. In this regard, there is a great need to develop a synthesis of composites of Au–Pt alloy

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nanostructures with low-density packing and suitable solid supports to ensure both the performance and durability of DMFCs. With the recent advent of virus-based bionanotechnology, various viruses have been utilized as biological templates (biotemplates) to synthesize functional nanomaterials. Functional nanostructures resulting from virus-based synthesis have attracted a lot of attention as novel nanoscale platforms due to their advantageous characteristics including their monodispersity, multiple valences, tunable structural features, biocompatibility, stability, and low-cost production.3133

The M13 virus (M13) is particularly interesting here. This virus, which infects bacterial host cells,

is 880 nm in length and 6.6 nm in diameter, consists of a single-stranded DNA enclosed by 2700 identical copies of major coat protein pVIII and capped with five copies of four different minor coat proteins (pIX, pVII, pVI and pIII) at the ends,34 and is stable in a wide range of pH, temperature and organic solvent conditions. Moreover, M13 is considered not harmful in humans and animals. Hence, it has been applied to various biomedical applications such as drug and gene delivery as well as tissue engineering.35-36 In addition, the virus can be engineered to have specific affinity toward selected metal precursors by having certain of its genes modified, with inserted DNA sequences.37-40 Recently, the Belcher group and other research groups have made significant contributions towards the synthesis of various nanostructures based on engineered M13 for various applications including semiconductor synthesis, energy storage, electric generators, and tissue engineering materials.31-32, 4144

The resulting M13 engineered with specific peptides allows them to bind and organize the

precursors, and nucleate metallic nanostructures as biotemplates. Biomineralization of metal nanostructures using peptides expressed on the virus surfaces has proven to be efficient and highly cost effective. On the one hand, biomineralization carried out using M13 by typical chemical deposition could lead to a lack of electrical pathways in electrochemical applications such as DMFCs. On the other hand, biomineralization through electrodeposition could secure electrical pathways by connecting the nanostructures on M13. Therefore, M13 viruses with nanostructures electrodeposited 3|Page ACS Paragon Plus Environment


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on their surfaces might provide excellent biotemplates to synthesize DMFC materials with engineered catalysts. To the best of our knowledge, electrodeposition-based biomineralization on viruses-modified surfaces has never been reported. Here, we report a novel fabrication of a virus-templated silicate sol–gel matrix (SSG) with an rGO dispersion to nucleate Au–Pt alloy nanostructures by electrodeposition. We demonstrated the use of the nanostructures as efficient electrocatalysts of the methanol oxidation reaction (MOR) for DMFC applications. The density of the nanostructures at the electrode surface was controlled with the incorporated viruses and its genetically modified peptide surfaces, which offered a convenient way to synthesize relatively less densely packed metal nanostructures on the biotemplates. We demonstrated the density and shape of the alloy nanostructures that affected the MOR performance to be highly influenced by the peptide sequences on the major coat protein of the virus. Interestingly, the incorporated viruses in the biotemplate did not change the electronic conductivity of the template with rGO and the alloy nanostructures. In addition, the M13 viruses infusion improved the colloidal stability of the rGO and contributed to the generation of an OH–-rich environment for an efficient MOR. 2.

Experimental Section

2.1.

Materials and Methods Graphite (powder 500s (% s–1)

(3),

where (dI/dt)t>500s is the slope of the linear portion of current decay and I0 is the current at the start of polarization back-extrapolated from the linear current decay. The poisoning rates were calculated to be 0.0212 and 0.0075% s–1 for the commercial Pt/C and SSG/M13Y3E/rGO/(Au58.9– Pt41.1) catalysts, respectively. The result further revealed the better poisoning tolerance of the SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalyst. To determine the stability of the SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalyst, 100 continuous cycles of the MOR were carried out using this catalyst (Figures 10C and D). After the 100 cycles, the peak current decreased by only 10.2 %, which indicated that the proposed SSG/M13Y3E/rGO/(Au58.9– Pt41.1) catalyst showed good sensitivity and stability toward the MOR. The durability of the catalyst has been recognized as one of the most important issues to be addressed before commercializing DMFCs. Thus the durability of the SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalyst was further evaluated in

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an accelerated durability test (ADT) by applying linear potential sweeps between 0.6 and 1.1 V at 100 mV/s in 0.5 M H2SO4 electrolyte at room temperature. For comparison, SSG/M13Y3E/rGO/Pt and SSG/M13Wild/rGO/(Au57.7–Pt42.3) catalysts were also studied under the same conditions. Figures S13A(a–f), B(a–f) and C(a–f) show the CVs of the SSG/M13Y3E/rGO/Pt, SSG/M13Wild/rGO/(Au57.7– Pt42.3), and SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalysts, respectively, at initial conditions and then every 250 ADT cycles up to the 1250th ADT cycle. After 250 cycles, the current densities in the hydrogen adsorption/desorption potential regions (–0.2 to 0 V) dropped dramatically with additional CV cycles for all three catalysts. ECSAs were generally observed to decrease with more CV cycles, predominantly during the first 500-750 cycles (Figure S13D). Specifically, after 250, 500, 750, 1000 and 1250 ADT cycles, the ECSAs of SSG/M13Y3E/rGO/Pt, SSG/M13Wild/rGO/(Au57.7–Pt42.3) and SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalysts decreased by 5.6, 10.8 and 12.7%, 58.1, 53.4 and 85.2%, 62.6, 55.9 and 81.3%, 65.3, 60.0 and 78.5%, and 67.5, 61.0 and 76.4%, respectively. Note that the ECSAs did not decrease significantly after 750 cycles. The overall ECSA loss for the three catalysts was on average about 68% after 1250 ADT cycles. Interestingly, the ECSA of the SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalyst (Figure S13C) increased a little bit after 500 cycles, suggesting that new Pt surface features were generated at that point during the cycling test. Pt nanostructures in all three catalysts would have been expected to grow and aggregate during the durability tests owing to Ostwald ripening2, 7, 65 causing the aggregation, coalescence and ECSA loss. Despite our method being very simple, easy to follow, and very convenient for fabricating nanostructures, the performances we obtained were comparable or superior to the previous results obtained from more complicated approaches. Moreover, the use of peptides expressed on the virus surfaces as a surfactant to fabricate metal nanostructures is highly cost effective not only because M13 is a kind of bacteriophage that enables low-cost mass production but also because the corresponding synthetic peptides that give similar effects to those we found for the fabrication are extremely expensive.



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4.

Conclusions In summary, we have demonstrated the preparation of an engineered M13 virus-incorporated

biotemplate on electrode surfaces and its use in the electrodeposition of highly efficient Au–Pt alloy nanostructures for the MOR. The alloy nanostructures on the biotemplate incorporating specifically M13Y3E exhibited significantly higher electrocatalytic activity than did the monometallic counterparts or those incorporating M13Wild or M134E. The SSG/M13Y3E/rGO/(Au58.9–Pt41.1) catalyst showed a larger ECSA and better MOR performance than did the commercial Pt/C catalyst, which we attributed to the improved dispersion of Au-Pt alloy nanostructures on the biotemplate that ensured fast mass transport during the reactions. But in terms of durability, present catalyst suffered after 800 s when compared to commercial Pt/C catalyst. The combination of the biotemplate and electrodeposition could offer a convenient way to control the density of the nanostructures at the electrode surface by allowing for the peptide functionalities and the incorporated virus concentration to be selected, which are essential for optimizing the electrocatalytic performances. The use of peptides expressed on the virus surfaces as a surfactant to fabricate metal nanostructures is highly cost-effective because corresponding synthetic peptides being able to give similar effects to the fabrication are extremely expensive. This simple approach can be extended to other metals and matrices and the fabricated templates should provide highly promising scaffolds for sensors and energy applications including batteries, supercapacitors, and fuel cells.

Associated Content Supporting Information SEM, SEM-EDX and XPS analysis of different modified electrodes; controlled experiments for MOR; comparison of ECSA and mass activities; comparison of different composition effect of Au-Pt nanostructures toward MOR; MOR at different scan rate study; electrochemical durability studies.


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Author Information Corresponding Author *E-mail: [email protected] Notes The authors declare no competing financial interest. Acknowledgements This work was partially supported by the Incheon National University (International Cooperative) Research Grant in 2012.

Figures

Figure 1. (a) Schematic illustration of M13wild, M13Y3E and M134E. (b) Schematic representation of SSG/M13Y3E/rGO/(Au–Pt) catalyst fabrication.



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Figure 2. (A to C1) SEM images of (A, A1) ITO/SSG/M13Y3E/rGO/Au, (B, B1) ITO/SSG/M13Y3E/rGO/Pt and (C, C1) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes at different magnifications. (D) EDX analysis of ITO/SSG/M13Y3E/rGO/(Au–Pt) electrode.

Figure 3. SEM images of (A) ITO/SSG/M13Y3E/rGO/(Au–Pt), (B) ITO/SSG/M13Wild/rGO/(Au–Pt) and (C) ITO/SSG/M134E/rGO/(Au–Pt) electrodes.


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*

*

*

*

*

*

*

*

50

60

(200)

(111)

* *

c

(200)

(111)

* * * *

b

a 10

20

30

40

(311)#

*

(311)

(002)

(220)#φ

*

(220)

d (002)

(111)#φ

(220)

ITO *# Au φ Pt

Intensity (a.u)

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


(200)#φ

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70

80

2 θ (Degree) Figure 4. XRD patterns of (a) ITO/SSG/M13Y3E/rGO, (b) ITO/SSG/M13Y3E/rGO/Au, (c) ITO/SSG/M13Y3E/rGO/Pt and (d) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes.



A

d

Mass activity (A/mg Pt)

2.0 1.5

Ι (mA)

e 1.0

b c

0.5

a

0.0 -0.5 -200

0

200 400

600 800 1000 1200

1.5

e

B

d b

1.0

0.5

c a 0.0 -1000 -800 -600 -400 -200

E vs. Ag/AgCl (mV)



350 300 250 200

e

150 100

d

50

c a

0 0

b 300

600

900

0

200 400 600

E vs. Ag/AgCl (mV)

C

400

1200

1500

1.5

b

D

1.0

0.5

a

0.0

-1000 -800 -600 -400 -200

0

200 400 600

E vs. Ag/AgCl (mV)

Time / Sec

Figure 5. CVs of (a) ITO/(Au–Pt), (b) ITO/SSG/(Au–Pt), (c) ITO/SSG/M13Y3E/(Au–Pt), (d) ITO/SSG/rGO/(Au–Pt) and (e) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes in (A) 0.5 M H2SO4 and in (B) 0.1 M CH3OH and 0.1 M KOH at a scan rate of 50 mV/s. (C) Amperometric i–t curves observed for A(a–e) in 0.1 M CH3OH and 0.1 M KOH at an applied potential of –0.3 V. (D) comparison of ITO/SSG/M13Y3E/rGO/(Au–Pt) electrode in the (a) absence and (b) presence of 0.1 M CH3OH in 0.1 M KOH at a scan rate of 50 mV/s.

1.5

c

0.5

a

0.0 -0.5 -1.0 -200

0

200

400

600

800

E vs. Ag/AgCl (mV)

1000 1200

1.5

B

1.0

0.5

0.0

b a

-1000 -800 -600 -400 -200

C

400

c

0


b


A 1.0

Ι (mA)

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

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200 400 600

E vs. Ag/AgCl (mV)

350 300 250 200 150

b

100

a

50 0 0

300

600

900

1200

Time / Sec

Figure 6. (A, B) CVs of (a) ITO/SSG/M13Y3E/rGO/Au, (b) ITO/SSG/M13Y3E/rGO/Pt and (c) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes in (A) 0.5 M H2SO4 and in (C) 0.1 M CH3OH and 0.1 M


1500

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KOH at a scan rate of 50 mV/s. (C) Amperometric i–t curves observed for A(b,c) electrodes in 0.1 M CH3OH and 0.1 M KOH at an applied potential of –0.3 V.

A

Ι (mA)

1.0


1.5

c b a

0.5

0.0

-0.5 -200

0

200 400 600 800 1000 1200

1.5

B

c

1.0

b a

0.5

0.0 -1000 -800 -600 -400 -200

0

200 400 600

E vs. Ag/AgCl (mV)

E vs. Ag/AgCl (mV)

Figure 7. CVs obtained at (a) ITO/SSG/M13Wild/rGO/(Au–Pt), (b) ITO/SSG/M134E/rGO/(Au–Pt) and (c) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes in (A) 0.5 M H2SO4 and in (B) 0.1 M CH3OH and

0.0

40 0

ECSA

ECSA/gPt

1.5 1.0 0.5 0.0

SSG/M13-Y3E/rGO/(Au–Pt)

2.0

SSG/M13-W/rGO/(Au–Pt) SSG/M13-4E/rGO/(Au–Pt)

80

2.5

ITO/(Au–Pt) SSG/(Au–Pt) SSG/M13-Y3E/(Au–Pt) SSG/rGO/(Au–Pt)

0.5

120

3.0

SSG/M13-Y3E/rGO/Pt SSG/M13-Y3E/rGO/Au

1.0

160

Peak Current (A/mg Pt)

1.5

200

SSG/M13-Y3E/rGO/(Au–Pt)

2.0

240

C 3.5 SSG/M13-W/rGO/(Au–Pt) SSG/M13-4E/rGO/(Au–Pt)

2.5

SSG/M13-Y3E/rGO/Pt SSG/M13-Y3E/rGO/Au ITO/(Au–Pt) SSG/(Au–Pt) SSG/M13-Y3E/(Au–Pt) SSG/rGO/(Au–Pt)

2

3.0

280

2

3.5

B 320 Area (m /g Pt)

A 4.0

SSG/M13-Y3E/rGO/Pt SSG/M13-Y3E/rGO/Au ITO/(Au–Pt) SSG/(Au–Pt) SSG/M13-Y3E/(Au–Pt) SSG/rGO/(Au–Pt) SSG/M13-Y3E/rGO/(Au–Pt) SSG/M13-W/rGO/(Au–Pt) SSG/M13-4E/rGO/(Au–Pt)

0.1 M KOH at the scan rate of 50 mV/s.

Area (cm )

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


Mass Activity

Figure 8. (A) ECSAs, (B) ECSAs per Pt gram and (C) mass activities mono- and bimetallic catalysts.



Figure 9. Schematic representation of MOR at ITO/SSG/M13Y3E/rGO/(Au–Pt) electrode.

1.5

b

A



400

1.0

0.5

a 0.0

B 300

200

b 100

a 0

-1000 -800 -600 -400 -200

0

0

200 400 600

2.0

600

900

1200

1500

2.0

C

Cycle 1

1.5

1.5

j (A)

1.0

300

Time / Sec

E vs. Ag/AgCl (mV)


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Cycle 100

0.5

D

1.0

0.5

0.0 -1000 -800 -600 -400 -200

0.0 0

200 400 600

E vs. Ag/AgCl (mV)

0

10 20 30 40 50 60 70 80 90 100

[Cycle Number]

Figure 10. (A) CVs of (a) ITO/Pt/C and (b) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes in (A) 0.1 M CH3OH and 0.1 M KOH at a scan rate of 50 mV/s. (B) Amperometric i–t curves observed for (a) ITO/Pt/C and (b) ITO/SSG/M13Y3E/rGO/(Au–Pt) electrodes in 0.1 M CH3OH and 0.1 M KOH at an applied potential of –0.3 V. (C) CVs obtained at ITO/SSG/M13Y3E/rGO/(Au–Pt) electrode in 0.1 M CH3OH and 0.1 M KOH at the scan rate of 50 mV/s with 1 to 100 cycles. (D) Corresponding calibration plot.


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Table 1. Electrochemical Parameters of MOR Derived from Various Modified Electrodes. Specific modified electrodes

ECSA

ECSA

onset

anodic

mass activity

2

(m /g

potential

peak

(A/mg Pt)

Pt)

(V)

potential

2

mass

(cm )

(mg 2

Pt/cm

)

If/Ib

(V)

ITO/(Au62.5–Pt37.5)

0.00532

1.18

22.19

–0.590

–0.010

0.1278

10.10

ITO/SSG/(Au63.3–Pt36.7)

0.00437

1.36

31.06

–0.570

0.238

0.9798

14.94

ITO/SSG/M13Y3E/(Au62.3–Pt37.7)

0.00463

1.38

29.93

–0.574

0.038

0.2760

11.13

ITO/SSG/rGO/(Au60.3–Pt39.7)

0.00322

1.31

40.81

–0.644

0.296

1.3093

10.66

ITO/SSG/M13Y3E/rGO/(Au64–

0.00210

0.36

17.2

–0.345

0.003

0.1336

5.59

0.00107

1.63

153.23

–0.642

–0.082

1.5428

10.37

0.00090

0.44

48.89

–0.525

0.021

1.0470

6.04

0.00269

1.22

45.53

–0.516

0.061

0.6840

-

0.00230

1.08

47.20

–0.479

–0.102

0.7790

-

ITO/SSG/M13Y3E/rGO/Au100

0.01333

0.25

1.88

-

-

-

-

ITO/SSG/M13Y3E/rGO/Pt100

0.01006

2.14

21.30

–0.570

0.152

0.4060

3.81

Commercial Pt/C

0.0051

-

-

–0.563

–0.563

0.2389

8.07

Pt36) ITO/SSG/M13Y3E/rGO/(Au58.9– Pt41.1) ITO/SSG/M13Y3E/rGO/(Au57.7– Pt42.3) ITO/SSG/M13wild/rGO/(Au57.7– Pt42.3) ITO/SSG/M134E/rGO/(Au61.1– Pt38.9)

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Nanoscale 2015, 7 (4), 1301–1307. 2.

Gnanaprakasam, P.; Jeena, S. E.; Selvaraju, T., Hierarchical Electroless Pt Deposition at Au

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Graphical abstract:

CH3OH Mass activity / A mg–1Pt

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Page 32 of 32

1.5

1.0

a : Au b : Pt c : Au–Pt

c

0.5

0.0

b a

-1000-800 -600 -400 -200 0 200 400 600

E vs. Ag/AgCl (mV)

–

CO2 + H2O + 6e

SSG/M13Y3E/rGO/(Au–Pt) Catalyst


M13 Virus-Incorporated Biotemplates on Electrode Surfaces To

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