File Name : fig. s1.tif

Caption : fig. s1 sem images of (a, b) co-s/cu-f, (c, d) zn-s/cu-f, and (e, f) cozn-s/cu-f.

File Name : fig . s2.tif

Caption : fig. s2 tem images of cozn-s/cu-f.

File Name : fig. s3.tif

Caption : fig. s3 nyquist plots at 1.4 v and -0.1 v in 1 m koh for (a) oer and (b) her, from 100 khz to 0.01 hz using ac perturbation voltage of 10 mv.

File Name : fig. s4.tif

Caption : fig. s4 (a) co 2<i>p</i> spectra, (b) zn 2<i>p</i> spectra, (c) s 2<i>p</i> spectra, and (d) o 1<i>s</i> spectra of cozn-s/cu-f before and after oer and her stability tests.

File Name : fig. s5.tif

Caption : fig. s5 xrd spectra of cozn-s/cu-f and after oer and her stability tests.

File Name : fig. s6.tif

Caption : fig. s6 xrd spectra of cozn-s/cu-f after (a) oer and (b) her stability tests at a high magnification showing the presence of cuo and cu(oh)<sub>2</sub>, respectively.