Preparing high-efficiency electrocatalyst through facile, low energy consumptive, and time-effective strategy is essential to the hydrogen generation via water electrolysis. Here, we report a galvanic replacement-mediated synthesis of highly active Co-Fe layered double hydroxides (Co-Fe LDHs) at room temperature as advanced electrocatalyst for water oxidation. The disc-like Co precursors were the first proposed as self-sacrificing templates for Co-Fe LDHs. By steady control of the carving of iron ions, the disc-like Co precursors are carved relaxedly and then formed to nanosheet-constructed Co-Fe LDHs. The Fe (II) ion is proved to a more preferable iron precursor than Fe (III) ion for Co-Fe LDHs nanosheets growth, owing to the "slow-growth" process. This catalyst shows a highly electrocatalytic activity towards the OER with low overpotential (110 mA cm(-2) = 270 mV), low Tafel slope (48.7 mV dec-1), and remarkable long-time stability. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.