Pre-deposited Co nanofilms promoting high alloying degree of Pd_xAu nanoparticles as electrocatalysts in alkaline media

High alloyed and well dispersed Pd_xAu nanoparticles are deposited on pre-deposited Co nanofilm substrates (Pd_xAu/Co-nanofilms/C) by using an immiscible ionic liquid (IL)/water interface. However, low alloyed Pd_xAu/C catalysts are formed without pre-deposited Co nanofilms through the same synthesis method. The high-alloyed Pd_xAu/Co-nanofilms/C catalysts demonstrate significantly increased activity for ethanol oxidation reaction (EOR) than low-alloyed Pd_xAu/C of the same Pd/Au composition, with the catalysts of low Pd/Au atom ratio (Pd:Au = 1:1) demonstrating the optimal activity. Notably, high alloyed degree of the Pd_xAu nanoparticles in the Pd_xAu/Co-nanofilms/C catalysts brings the lattice expansion of Pd, causing an up-shift of the d-band center, which results in the enhancement of OH⁻ adsorption and correspondingly promotes electro-oxidation of ethanol excluding the effect of Co nanofilm substrates. Differently, the enhancement activities of the Pd-Au bimetallic system for oxygen reduction reaction (ORR) are almost not affected by the alloying degree and only dependent on Pd/Au atom ratios, with the catalysts of low Pd/Au atom ratio (Pd:Au = 1:1) displaying the highest ORR mass activity, respectively. These results exhibit the specific dependence between the different electrochemical process and the physical parameters for the Pd-Au bimetallic system. © 2020 Hydrogen Energy Publications LLC.