Supplementary Information:

Interface engineering for high-performance direct methanol fuel cells using multiscale patterned membranes and guided metal cracked layers

Segeun Janga,b,⊥, Sungjun Kimc,d,⊥, Sang Moon Kime, Jiwoo Choia,b, Jehyeon Yeona,b, Kijoon Banga,b, Chi-Yeong Ahnc,d, Wonchan Hwangc,d, Min Herc,d, Yong-Hun Chof,*, Yung-Eun Sungc,d,*, and Mansoo Choia,b,*

a Global Frontier Center for Multiscale Energy Systems, Seoul National University, Seoul 08826, Korea

b Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea

c Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Korea

d School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Korea

e Department of Mechanical Engineering, Incheon National University, Incheon 22012, Korea

f Department of Chemical Engineering, Kangwon National University, Samcheok 24341, Korea

Corresponding Authors*E-mail: mchoi@snu.ac.kr (M. Choi), ysung@snu.ac.kr (Y.-E. Sung), yhun00@kangwon.ac.kr (Y.-H. Cho)

Author Contributions⊥S. Jang and S. Kim contributed equally to this work.

Figure S1. SEM images of the surface of the multiscale prism-patterned mold

Figure S2. AFM images of the surface of the prism-patterned (P-10) and multiscale prism-

patterned (MP-10) membranes.

Figure S3. Relative membrane-electrode interface area of the flat reference, prism-patterned

(P-10) and multiscale-patterned (MP-10) membrane.

Figure S4. Single cell polarization curves under hydrogen-oxygen operation of all the MEAs

including MEAs with patterned-membranes (P-10 and MP-10) and MEAs with patterned-

membranes containing a Au layer with guided cracks (P-10-Au and MP-10-Au).

Figure S5. CO stripping voltammograms of the Pt black and PtRu black catalyst layers of the

reference MEA.

To check the influence of the adsorption of –OH species on the hydrogen

adsorption/desorption process of the PtRu, CO stripping voltammetry was performed on Pt

black as well as PtRu black. As shown below, in the case of the Pt black, the ECSA values

calculated from the H2 desorption peak (15.99 m2 g-1) and COad oxidation peak (16.32 m2 g-1)

are almost the same. However, in the case of the PtRu black, the ECSA calculated from the

H2 desorption peak (33.52 m2 g-1) is considerably lower than that from the COad oxidation

peak (49.11 m2 g-1). This results mean the adsorption of –OH species really hinder the

adsorption of hydrogen. Based on this observation, CO stripping voltammetry was selected

for ECSA calculation.

Figure S6. Cyclic voltammogram (CV) of the anode catalyst layers of all the MEAs

including MEAs with patterned-membranes (P-10 and MP-10) and MEAs with patterned-

membranes containing a Au layer with guided cracks (P-10-Au and MP-10-Au).

Cyclic voltammetry (CV) was carried out to analyze the effect of incorporating guided

cracked gold layer into the patterned MEAs on the PtRu utilization of the anode catalyst

layer. Fully humidified hydrogen was fed to the cathode (Pt black electrode), serving as the

RE and the CE, and fully humidified nitrogen was supplied to the anode (PtRu black

electrode), serving as the WE. This measurement was conducted at a cell temperature of 30

°C and the voltage sweep range was 0.05–1.20 V at a scan rate of 100 mV s -1. From the CV

results, we can see that the incorporation of a cracked metal barrier into the MEAs does not

affect Pt utilization and the number of available active sites

Figure S7. Single cell polarization curves under the 1.5 M methanol-oxygen (or air)

operation of reference MEA and multiscale patterned MEA with Au layer with guided cracks

(MP-10-Au). The flow rate of oxygen and air were identical (200 ml min-1).

Figure S8. (a) Single cell polarization curves and (c) EIS spectra of the MEAs including

reference MEA, MEA with intact Au layer (Intact Au), MEA with randomly cracked Au layer

(Random Au) and MEAs with patterned membranes containing a Au layer with guided cracks

(P-10-Au and MP-10-Au).

Figure S9. SEM images of the surfaces of the intact Au layer and randomly cracked Au layer

on flat membrane.

Figure S10. Tilted (45°) SEM images of P-10 (left) and MP-10 (right) patterned membranes

with guided silver cracked layer.