PDF《Supporting Information》

S1 Supporting Information Carbon-Coated Hollow Mesoporous FeP Microcubes: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Xiaohua Zhu,a b Mengjia Liu,b Yang Liu,b Ruwen Chen,b Zhou Nie,*a Jinghong Li,*b Shouzhuo Yaoa a State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, ChangSha

410082 (P.

R. China) b Department of Chemistry, Beijing Key Laboratory for Microanalytical Methods and Instrumentation Tsinghua University, Beijing

100084 (China) *Corresponding Author: E-mail: [email protected] E-mail: [email protected] S2 Experimental Section Chemicals Polyvinylpirrolydone (PVP, K30, MW ≈

40 000), potassium ferrocyanide K4Fe(CN)6, hydrochloric acid (HCl), Diammonium phosphate (NH4)2HPO4・H2O were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Pt/C (20 % Pt on Vulcan XC-72R) and Nafion (5 %) were purchased from Sigma-Aldrich. All chemicals were used as received without further purification. All solutions were prepared with double distilled water. Synthesis of Prussian blue microcubes Prussian blue (PB) microcubes were prepared according a facile solution method.[1] In a typical procedure, PVP (10.0 g) and K4[Fe(CN)6]・3H2O (0.55 g) were added to a HCl solution (0.1 M,

200 mL) under magnetic stirring. After the mixture was stirred for

30 min, a clear solution was obtained. The bottle was then placed into an electric oven and heated at

80 oC for

24 h. The obtained blue product was separated by centrifugation and washed several times with distilled water and absolute ethanol and finally dried in a vacuum oven at

60 oC for

12 h. Preparation of Fe3O4 microcubes and HMFeP@C To convert the PB microcubes into Fe3O4 microcubes, the as-synthesized PB was heated at

500 ?C with a temperate ramp of

2 ?C min-1 for

6 h in N2. To prepare HMFeP@C, the obtained Fe3O4 microcubes and (NH4)2HPO4・H2O were put at two separate positions in a porcelain boat with (NH4)2HPO4・H2O at the upstream side of the furnace. The molar ratio for Fe to P was 1:50. Subsequently, the samples were heated S3 at

350 °C for

120 min in a static Ar atmosphere, and then naturally cooled to ambient temperature under Ar.[2] Characterization X-ray diffraction (XRD) patterns were collected on a Bruker D8 Advanced X-ray diffractometer with Ni filtered Cu Kα radiation (λ = 1.5406 ?) at a voltage of

40 kV and a current of

40 mA. Field-emission scanning electron microscope (FESEM) images were acquired on a JEOL JSM-6700F microscope operated at

5 kV. Transmission electron microscopy (TEM) images were taken on JEM-2010 and JEOL JEM-2100F microscopes. Energy-dispersive X-ray (EDX) analysis and elemental mapping were performed using the energy-dispersive X-ray spectroscope attached to the JSM-6700F and JEM-2100F, respectively. Nitrogen sorption measurements were performed on an Autosorb 6B apparatus at liquid N2 temperature. Raman spectroscopy was performed on a Renishaw RM2000 microscopic confocal Raman spectrometer (Gloucestershire, United Kingdom) using green (514 nm) laser excitation. Preparation of Working Electrodes Catalyst ink was prepared by dispersing

10 mg of catalyst into

900 ?L of ethanol solvent containing

100 ?L of

5 wt % Nafion and sonicated for

30 min. Then

5 ?L of the catalyst ink (containing

50 ?g of catalyst) was loaded onto a glassy carbon electrode (GCE) of

3 mm in diameter (loading ca. 0.72 mg cm-2). Electrochemical Measurements All the electrochemical measurements were conducted using a CHI1011 electrochemical workstation (CH Instruments, China) in a typical three-electrode setup S4 with an electrolyte solution of 0.5 M H2SO4, a Pt wire as the counter electrode, and an Ag/AgCl-saturated KCl as the reference electrode. Linear sweep voltammetry (LSV) was conducted in 0.5 M H2SO4 with a scan rate of