A new catalysts electrode was prepared by in situ controllable deposition of Pd shell layer on the gas diffusion layer (GDL) supported Ni(OH)(2) nanoparticles using atomic layer deposition (ALD) technology. High resolution transmission electron microscope confirmed that the Ni(OH)(2) core was coated by several atomic layers of Pd. The core-shell Ni(OH)(2)@Pd catalysts with different thickness of Pd shell are easily prepared by controlling ALD cycle. Electrochemical tests showed that the 100-Ni(OH)(2)@Pd/GDL catalyst prepared via 100 ALD cycles presented the highest catalytic activity for ethanol electro-oxidation reaction (EOR). The peaking current density of Ni(OH) (2)@Pd/GDL was 1439 mA mg(Pd)(-1), which was about 2.75 times as high as that of Pd/GDL (522 mA mg(Pd)(-1)). The shift in binding energy of the XPS peak of Pd in Ni(OH)(2)@ Pd catalyst confirmed the strong interaction between the Pd shell and the Ni(OH)(2) core. We suggested that the high catalytic activity of Ni(OH)(2)@ Pd/GDL catalyst layer may be due to following factors: high Pd dispersion arising from the core-shell structure, high Pd utilization because of the in situ deposition of Pd on catalyst layer and the interaction between the Pd shell and the Ni(OH)(2) core. Herein, the ALD technology exhibits a promising application prospect for preparing core-shell structure and precisely controlling shell thickness of nano-composite as an electro-catalyst toward EOR. (C) 2017 Elsevier B.V. All rights reserved.