Síntese de eletrocatalisadores de paládio para produção de hidrogênio em eletrolisador ácido-alcalino

Abstract

This work aims to optimize the synthesis procedure for palladium nanocatalysts supported on carbon black Vulcan XC-72R (Pd/C) by chemical reduction with sodium formate, to maximize their performance in ethanol electro-oxidation and their application in an acid-alkaline electroreformer to produce green hydrogen. For this purpose, the influence of synthesis parameters, including reducing agent concentration, pH, reaction volume, and, ultimately, the atmosphere used, was investigated. The prepared materials were characterized by Inductively Coupled Plasma Optical Emission Spectrometry to confirm their composition, X-Ray Diffraction to assess crystallinity and average crystallite size, and Transmission Electron Microscopy to evaluate the nanoparticle size distribution. Next, the materials were tested for the reaction under study in a three-electrode cell to assess their electrochemical activity, a parameter directly related to green hydrogen production. Finally, the best material was tested in the acid-alkaline electroreformer, and an aliquot was collected to estimate the products formed and their distribution, with a view to their techno-economic impact on the process. The results demonstrated that pH is a crucial variable for achieving smaller particle sizes and more homogeneous distributions, with particle sizes in the range of 8-10 nm. This trend was further enhanced by using a 90:10 (vol.%) N2:H2 atmosphere, which halved the average particle size and notably increased particle size homogeneity on the support. These improved morphostructural properties resulted in the best oxidation performance, reflected in a maximum current density of 280 mA cm2. Furthermore, in spontaneous operation, stimulated by the favorable pH gradient, a maximum power density of 6 mW cm2.