The controlled surface deposition of a robust and high-
performance nanostructured copper-oxide (
CuO
x
-NLs) electrocatalyst for
water oxidation is presented. The material exhibits a characteristic leaf-type
morphology and self-assembles on a copper substrate by straightforward
constant-current anodization. The oxygen onset occurs at about 1.55 V versus
RHE (
η
= 320 mV), which is 400
−
500 mV less than for amorphous Cu-oxide
fi
lms. A Tafel slope of 44 mV dec
−
1
is obtained, which is the lowest observed
relative to other copper-based materials. Long-term catalytic performance and
stability tests of the electrocatalytic
CuO
x
-NLs sample show a stable current
density of >17 mA cm
−
2
for oxygen evolution, which was sustained for many
hours