Preparation of bimetallic nanozeolite-supported Pt-Cu nanoparticles modified carbon paste electrode for enhanced formaldehyde electrooxidation

Fuel cells are being considered as an attractive electricity generation technology, which supplies very effective and direct conversion of chemical energy into electricity. To develop fuel cells, theanodic catalysts have been an important challenge. Therefore, some research fields have been dealing with the challenges to synthesis of cost effective and highly active catalyst for oxidation process of fuel in the fuel cells [1]. Formaldehyde fuel cells have been extensively consideredbecause formaldehyde is an intermediate in the methanol oxidation. Also, it has practical application for metallizing non-conducting surfaces, especially in production of printed circuit boards [2]. Pt-based electrocatalysts are regarded as ideal catalyst for formaldehyde oxidationdue to their prominent properties in the catalytic processes. However, Pt is one of the noble metals and high cost of noble metals can restrict their wide applications. Therefore, it is worthwhile to decrease the required amount of Pt in the electrocatalysts. The addition of asecondary element, in oxidized form or metallic form, into Pt catalyst is an effective way to reduce the amount of Pt. Also, bimetallic catalysts can improve the activity and stability of Ptbasedcatalysts due to change of Pt-Pt bond distance, d-band center shift, and Pt skin effectwhich result into lattice shrinking or lattice strain [3]. In the bimetallic systems like monometallic systems, the use of supporting material such as zeolite has various advantages suchas stabilizing the nanoparticles against aggregation and achieving the highest possible electrode surface area which results in remarkable catalytic activity and efficiency. In this work, we synthesized NaX nanozeolite and used it for the first time for preparation of bimetallic Xnanozeolite-supported Pt-Cu nanoparticles modified carbon paste electrode (Pt-Cu-XNZ/CPE). SEM image of Pt-Cu-XNZ/CPE indicated the layer of irregular flakes of graphite powder and dispersed white nanoparticles which this uniform dispersion can be assigned to presence of nanozeolite on the electrode surface. The Cyclic voltammogram of Pt-Cu-XNZ/CPE was recorded in 0.5 M H2SO4 solution at 0.05 Vs−1. The characteristic peaks of Pt surface (Pt-Hredox peaks) at potential range of -0.2-0 V are assigned to atomic hydrogen adsorption on Pt surface. Appearance of these peaks confirm that platinization of the Cu nanoparticles surface has been achieved. The electrocatalytic activity of as-prepared Pt-Cu-XNZ/CPE toward formaldehyde oxidation was studied in an aqueous solution containing 1.5 M formaldehyde and0.5 M H2SO4 at a scan rate of 0.05 V.s–1 using cyclic voltammogram. It can be seen that formaldehyde oxidation exhibits the double voltammetry peaks that appear in the forward scan(Peak I) with peak potential of 0.72 V and reverse scan (peak II) with peak potential of 0.46 V. In summary, we prepared nanozeolite-supported Pt-Cu-XNZ/CPE for the first time with galvanic replacement method without using any reagent. This electrode indicated remarkably catalyticactivity including decreasing oxidation overpotential and increasing oxidation peak currents toward formaldehyde oxidation.

Keywords:

Bimetallic , Electrooxidation , Formaldehyde