Electrocatalysts galvanic displacement

Galvanic displacement method is also often used for synthesizing catalysts. By this method, low Pt-content electrocatalysts can be obtained. For example, a carbon-supported core—shell structured electrocatalyst with bimetallic IrNi as the core and platinum monolayer as the shell has been successfully synthesized using this method. In this synthesis, IrNi core supported on carbon was first synthesized by a chemical reduction and thermal annealing method and a Ni core and Ir shell structure could be formed finally. The other advantage of this method is that the Ni can be completely encased by Ir shell, which will protect Ni dissolve in acid medium. Secondly, IrNi PtML/C core—shell electrocatalyst was prepared by depositing a Pt monolayer on the IrNi substrate by galvanic displacement of a Cu monolayer formed by under potential deposition (UPD). 

Most recently, PIml electrocatalysts were systematically studied for the electrooxidation of methanol and ethanol [108]. PIml was deposited on different substrates via the galvanic displacement of a Cu UPD monolayer, employing five single-crystal surfaces (Au(lll), Pd(lll), Ir(lll), Rh(lll), and Ru(OOOl))... 

A typical PIml electrocatalyst is prepared by placing a mcMioIayer of Pt atoms rai metal nanoparticles using galvanic displacement of an underpotentially deposited (UPD) Cu monolayer by a Pt monolayer [3,7]. Underpotential deposition describes the formatiOTi of a submonolayer or monolayer of a metal on a foreign metallic substrate at potentials positive to the reversible Nemst potential, that is, before bulk deposition can occur [8]. The experimental setup for PtML deposition on an electrode consists of a cell with several compartments one used for Cu UPD, one for rinsing the electrode after emersion from CUSO4 solution, and one for displacement of a Cu monolayer upon electrode immersion in Pt " solution. The cell is under an inert gas (Ar or N2) and facilitates all operations in an 02-free environment. 

An important factor affecting the performance of DMFCs is the kinetics of catalyst. Platinum (Pt/C) is the most effective catalyst for oxygen reduction reaction but it is not selective towards ORR in presence of methanol. The addition of yttrium to Pt increases the ORR activity and are promising ORR electrocatalyst [207]. Carbon supported PtY(OH)3 hybrid catalyst are developed with dynamic spillover of metal oxide [208]. Recently, catalyst for DMFC Pt Pd/C NP was prepared by the galvanic displacement reaction between Pt and Pd. A simple synthesis strategy was followed to prepare carbon based [209] and carbon-supported Pd nanostructure [190]. A higher methanol tolerance of Pt Pd/C with less Pt content than Pt/C suggests that it is potential alternative cathode electrocatalyst for DMFCs [190]. 

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