A Method for the Synthesis of Platinum Nanoparticles with Defined Crystalline Orientations and Their Catalytic Activity towards Nitrogen and Carbon Monoxide Oxidations

Abstract

This work develops a new electrochemical method for thin layer platinum catalysts containing platinum particles at nanometer levels (from 5 to 38 nm) without using polymer or chemical capping agents. The process does not required chemical platinum ion precursors since soluble species are produced by an exclusive square wave potential program in strong acid media. Preferential (111), (110) and (100)-oriented nanoparticles are achieved by selecting the final value of reduction potential at which the electrochemical hydrogen occurs; i.e. −2 V, −1V or −0.1 V vs RHE. The electrocatalytic activity toward both nitrite and carbon monoxide oxidation is analyzed on these new surfaces. (111)-oriented platinum nanoparticles exhibit the lowest onset potential for carbon monoxide oxidation, 0.66 V, but the largest susceptibility toward surface poisoning, showing a 370 μC cm−2 anodic charge density for 8 min adsorption at 0.60 V. (100)-oriented platinum is the most tolerant upon surface poisoning but the less efficient toward carbon monoxide oxidation in perchloric acid, 312 μC cm−2 under identical conditions. There is no effect on the surface crystallographic orientation for nitrite adsorption and oxidation because of the nature of the stable adsorbed species, NOads and OHads, formed on each platinum nanoparticles.