Cu/Fe_3O_4 catalyst for water gas shift reaction: Insight into the effect of Fe~(2+) and Fe~(3+) distribution in Fe_3O_4

摘要

Two precursors, namely, p-CFO-T (tetragonal) and p-CFO-C (cubic), were fabricated by a solgel method via citric acid and poly(vinyl alcohol) complexation, respectively. After H-2-reduction, the two were converted to Cu/Fe3O4 catalysts of different complexions, which are named as CFO-CA and CFO-PVA, respectively. The distribution of Fe2+ and Fe3+ in the Cu/Fe3O4 catalysts was studied by Raman and XPS techniques. It was disclosed that the distribution of Fe2+ and Fe3+ in Fe3O4 has an effect on Cu-Fe3O4 interaction and catalyst surface basicity. Compared to CFO-PVA, CFO-CA has a larger amount of Fe3+, which mostly sits at the octahedral sites, leading to stronger Cu-Fe3O4 interaction, and a larger amount of catalyst surface sites that are of weak basicity. As a result, the critical elementary steps of WGS reaction, viz. water dissociation, -COOH decomposition and CO2 desorption are promoted as reflected in the lower E-a and higher catalytic activity of CFO-CA. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.