Supporting information for: Nanoporous metals by dealloying multicomponent metallic glasses Jinshan Yu, Yi Ding, Caixia Xu, Akihisa Inoue, Toshio Sakurai and Mingwei Chen * Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China Emial: mwchen@imr.tohoku.ac.jp Experimental Preparation of nanoporous Pd A classical three-electrode setup (Iviumstat electrochemical analyzer, Ivium Technology) was employed to dealloy the Pd 30 Ni 50 P 20 glassy ribbons using Ag/AgCl electrode as the reference. A section of Pd 30 Ni 50 P 20 ribbons were placed as the working electrode and a pure Pt sheet positioned parallel to the Pd 30 Ni 50 P 20 sample was used as the counter electrode. The electrolyte is 1mol/L H 2 SO 4 which was prepared from reagent grade chemical and Nanopure deionized water with a special resistance of ~18.2M. The optimized potential for dealloying the Pd 30 Ni 50 P 20 metallic glasses ranges from 0.8V to 0.83V. All electrochemical experiments were carried out at room temperature. The Pd 30 Ni 50 P 20 glassy ribbons were chemically cleaned with acetone using the ultrasonic agitator and followed by cleaning with deionized water. The dealloyed samples were taken out of the solution and rinsed with deionized water for several times and then dried. The same classical three-electrode 1
setup and procedure were used to dealloy the glassy Au 35 Si 20 Cu 28 Ag 7 Pd 5 Co 5 ribbons in 1mol/L H 2 SO 4. Sample characterization The microstructure and chemical composition of the Pd 30 Ni 50 P 20 glassy ribbons and dealloyed samples were characterized by a JEOL JSM-7001F scanning electron microscope equipped with an Oxford X-ray energy dispersive spectroscopy. A Philips CM300 field emission gun (FEG) high-resolution transmission electron microscope (HRTEM) was employed for TEM and HRTEM observations with an acceleration voltage of 300kV. Samples for the electron microscope characterization were prepared by ultrasonic dispersion of the fully dealloyed Pd 30 Ni 50 P 20 ribbons with 10mL ethanol in a 30mL conical flask. Then, the suspension was dropped on a conventional carbon-coated copper grid and dried in air before analysis. AES spectra and cross-sectional concentration profiles were measured by a JEOL JAMP-7100E Auger electron spectrometer. The XRD patterns were recorded using a Rigaku RINT- Ultima X-ray diffractometer with Cu K radiation (=0.154050nm). Formic acid electro-oxidation and CO electro-oxidation The electrochemical properties for formic acid electro-oxidation were performed in a standard three-electrode electrochemical cell with a CHI 1130A electrochemical workstation. The as-prepared nanoporous palladium was employed as the working electrode, using a reversible hydrogen electrode (RHE) and a Pt gauze as the reference electrode and counter electrode, respectively. All potential values in the text were recorded versus a RHE. Cyclic voltammograms were recorded in 0.1 M HClO 4 and mixed solution of 0.1 M HClO 4 and 0.1 M HCOOH at a scan rate of 50 mv s -1. 2
Both solutions were purged with high pure nitrogen (99.999%) for 10 min prior to measuring. The electrochemical active surface area of nanoporous Pd was measured by CO electrooxidation experiments. CO was adsorbed onto the sample surfaces in 0.1 M HClO 4 by bubbling the solution with CO for 30 min. The electrode was then transferred into a clean 0.1 M HClO 4 solution where CO stripping CVs were carried out. All CVs were performed at a scan rate of 50 mv/s (Fig. S3). 3
Figure S1 XRD pattern of Pd 30 Ni 50 P 20 metallic glass ribbons, which confirms a truly amorphous state of the sample. 4
a Porous layer Glassy substrate 5µm b 5µm c 50nm Figure S2 Cross-sectional SEM micrographs of dealloyed Pd 30 Ni 50 P 20 metallic glass. (a) Cross-sectional SEM micrograph of the sample after dealloying for 2000 seconds. (b) Cross-sectional SEM micrograph of the sample after dealloying for 3000 seconds. (c) High magnification SEM micrograph taken from the central region of the fully dealloyed ribbon shown in (b), revealing the nanoporous structure similar to the sample surface. 5
0.0010 0.0005 I/A 0.0000-0.0005-0.0010 13 m 2 /g 0.0 0.2 0.4 0.6 0.8 1.0 1.2 E/V vs RHE Figure S3 Electrochemical stripping curve of CO adsorbed on the nanoporous palladium surfaces, which allows an estimation of the electrochemical active surface area to be around 13 m 2 /g (Pd). 6