A bifunctional electrocatalyst of PtNi nanoparticles immobilized on three-dimensional

carbon nanofiber mats for efficient and stable water splitting in both acid and basic media

Jiawei Chen, Juan Wang, Jiadong Chen, Lina Wang*

Key Laboratory of Advanced Textile Materials and Manufacturing Technology of the

Ministry of Education, College of Materials and Textiles, Zhejiang Sci-Tech University,

Hangzhou, 310018, P. R. China, Tel: 86-571-86843871, Fax: 86-571-86843255, E-mail:

lnwang@zstu.edu.cn

KEYWORDS (carbon nanofibers; PtNi nanoparticles; water splitting; acid and basic media)

Fig. S1 Enlarged TEM images of (a) Ni/CNFs and (b) PtNi/CNFs.

Fig. S2 Nitrogen adsorption/desorption isotherms and corresponding pore size distribution of

(a, b) CNFs and (c, d) PtNi/CNFs.

Fig. S3 Electrochemical capacitance measurements for the estimation of the relative

electrochemical active surface area upon HER in 0.5 M H2SO4. Cyclic voltammograms in the

region of 0.27-0.37 V vs RHE of (a) Pt/CNFs, (b) Ni/CNFs and (c) PtNi/CNFs. (d) The

differences in current density of 0.32 V vs RHE plotted as a function of scan rates.

Fig. S4 (a) Polarization curves of the PtNi/CNFs before and after 1000 cyclesin 0.5M H2SO4, inset in (a) is the CV curves of PtNi/CNFs before and after 1000 cycles. (b) The TEM image of the morphology of the PtNi/CNFs membrane after stability test for 10 h in 0.5 M H2SO4.(c) Polarization curves of the PtNi/CNFs before and after 500 cycles in 1M KOH, inset in (c) is the CV curves of PtNi/CNFs before and after 500 cycles at a scan rate of 100 mV s -1. (d) The TEM image of the morphology of the PtNi/CNFs membrane after stability test for 10 h in 1M KOH.

Fig. S5 (a) Changes of element content of Pt and Ni for the PtNi/CNFs before and after electrochemical stability test through the EDS spectra; (b) TEM images of PtNi/CNFs.

Fig. S6 (a) HAADF-STEM images, (b) the corresponding STEM-EDS mapping images and (c, d)

line-scan EDX spectra of the PtNi/CNFs after the HER stability test in 0.5 M H2SO4.