Controlled decoration of Pd on Ni(OH)2 nanoparticles by atomic layer deposition for high ethanol oxidation activity.

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. [ABSTRACT FROM AUTHOR]