Cairo University

MTPR Journal

 

Enhanced Electrocatalytic Oxidation of Formic Acid at Iron and Nickel Oxides Nanoparticles-Modified Platinum Surfaces

2019-04-21
Bilquis Ali Al-Qodami 1, Sayed Y. Sayed 1, Nageh K. Allam 2, Ahmad M. Mohammad 1
1Chemistry Department, Faculty of Science, Cairo University, Cairo 12613, Egypt
2Energy Materials Laboratory, School of Sciences and Engineering, The American
University in Cairo, New Cairo 11835, Egypt

Vol./Issue: 19 , id: 302

Electrocatalytic oxidation of small organic molecules has recently gained more attention because of its application in power conversion technologies.The formic acid electro-oxidation (FAO); the principal anodic reaction in the direct formic acid fuel cells (DFAFCs), is usually catalyzedon either Pt or Pd-based surfaces.Generally,Pd-based catalysts exhibit much higher catalytic activity toward FAO and less intermediates' poisoning than Pt-based catalysts butare, unfortunately, subjected to acute deactivation;making them unsuitable for commercial purposes. On the other hand, Pt-based catalysts which have been proven more durable than Pd catalysts (albeitof less catalytic activity)for FAO represent the ideal choice so far for FAO. At Pt-based catalysts, FAO proceeds in a dual-pathway mechanism;the direct(dehydrogenationdesirableless overpotential) and indirect (dehydration undesirable  higher overpotential) oxidation avenues [1]. The indirect pathway of FAO involves the catalytic poisoning of the Pt surface with CO intermediate that is produced "non-faradaically" at open circuit potential. This poisoning is the main dilemma deteriorating the performance of DFAFCs as it severely lowers the energy and power densities of the cells.Herein, we propose a new catalyst composed of iron and nickel oxides nanoparticles andprepared by the layer-by-layer electrodeposition technique on Pt surfaces.Thedepositionsequence of the catalyst’singredientsis optimized to attain the highest catalytic activity and stability toward FAO. The transition metal oxide nanostructures assisted in mediating the reaction mechanism via speeding the charge transfer and in imparting a geometrical immunity to the Pt surface mitigating the CO poisoning which ultimately improved the catalyst's durability. Various electrochemical and materials characterizationtechniques including the cyclic voltammetry, chronoamperometry,field- emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were all combined to assess the catalytic activity and stability of the catalyst and further to report the catalysts' morphology, composition and structure.