nano-enhanced microbial electrochemical cells xie... · nano-enhanced microbial electrochemical...

Nano-Enhanced

Microbial Electrochemical Cells

Xing Xie, Craig S. Criddle, Yi Cui

Stanford University

Nov. 5, 2013

SNO Conference 2013

Microbial Electrochemical Cells (MECs)

• Energy: organic matter electricity

• Electrons: microorganisms electrode

2

2

1

3

Three pathways for extracellular electron transfer

1. Direct membrane contact

2. Electron mediators

3. Microbial nanowires

(Logan, Nat Rev Microbiol, 2009; Lovley, Nat Rev Microbiol, 2006)

More efficient

electron transfer

Microbial Bio-Electrodes

• Conductive

• Stable (chemical & bio)

• Biocompatible

• Macroscale porous structure

• Affinitive electrode surface

3

More microbes for

electron transfer

Carbon Nanotube (CNT)-Textile Synthesis

• A simple and scalable process

4

+ water + surfactantsonication

CNT inkCNT powder

dry

Hierarchical Structure of CNT-Textile

5

Macroscale

porous

textile

Microscale

porous

CNT

coating

~200 nm

• Conductive

– CNTs: 2000~4000 S/cm

– CNT-textile fiber (as a homogeneous solid material): ~50 S/cm

• Diameter of CNT-textile fiber: ~20 μm

• Thickness of CNT coating: 200 nm

– CNT-textile sheet (2 mm thick): ~1 Ω/sq

• Stable

– Mechanical force

– Wash

– Heat

– Acid

– Base

Physical and Mechanical Properties of CNT-Textile

6

(Hu, Nano Lett, 2010)

MFC Experimental Setup

7

• H-shaped classic reactor

• Anode

– Carbon cloth vs. CNT-textile

• Cathode

– Pt on Carbon cloth

• Separator

– Anion exchange membrane

• Feeding

– Glucose (1 g/L)

• Inoculum (bacteria source)

– Wastewater from Palo Alto Regional Water Quality Control Plant

500 μm

Carbon cloth

Biocompatibility

8

Evidence of colonization on CNT surface in MFCs

• Scanning Electron Microscope (SEM)

Macroscale Porous for Internal Colonization

9

• Cross-section of the anodes after 50 days of operation

Carbon cloth vs. CNT-textile

Biofilm-electrode interfacial area increased by ~10 times

Biofilm

Graphite fibers

Affinitive Electrode Surface

10

• Rough and soft

1 Direct membrane contact

• Microscale porous

2 Electron mediators

3 Microbial nanowires

1

3

2

Carbon cloth vs. CNT-textile

2

13

Affinitive Surface for Microbial Attachment

11

• Mechanical binding test

Carbon cloth vs. CNT-textile

Original:

After 5 mins

sonication and

10 s vortex

agitation:

Affinitive Surface for Electron Transfer

12

• Electrochemical impedance spectroscopy (EIS)

Carbon cloth

~30 ΩCNT-textile

~300 Ω

vs.

Diameter of the semicircle Electron transfer resistance

Resistance Efficiency

• Linear staircase voltammetry (LSV)

Maximum Current Output

13

2.6 times

CNT-textile (7.2 A/m2)

Carbon cloth (2.8 A/m2)

vs.

Internal colonization

Affinitive electrode surface

14

Modification 1

CNT-textile CNT-sponge

Random pore size Uniform &Tunable

Individual fibers 3D frameworkvs.

15

Modification 2

CNT-sponge Graphene-sponge

Cost:

100 vs. 1

More efficient

electron transfer

Summary

• Conductive

• Stable (chemical & bio)

• Biocompatible

• Macroscale porous structure

• Affinitive electrode surface

16

More microbes for

electron transfer

Acknowledgement

• Collaborators

– Prof. Zhenan Bao

– Liangbing, Mauro, George, Guihua, Yuan, James, Meng, Nian, Desheng

• Funding

– Stanford SOE/CEE Fellowship - Larry C. K. Yung Fellowship

– Stanford Graduate Fellowship - David and Lucile Packard Foundation Fellowship

– Stanford Interdisciplinary Graduate Fellowship - Fan Fellowship (A/P Scholars)

• SNO Student Award

17

Thank you!

18