Cu/Fe3O4 catalyst for water gas shift reaction: Insight into the effect of Fe2+ and Fe3+ distribution in Fe3O4

Two precursors, namely, p -CFO- T (tetragonal) and p -CFO- C (cubic), were fabricated by a sol-gel method via citric acid and poly(vinyl alcohol) complexation, respectively. After H 2 -reduction, the two were converted to Cu/Fe 3 O 4 catalysts of different complexions, which are named as CFO-CA and CFO-PVA, respectively. The distribution of Fe 2+ and Fe 3+ in the Cu/Fe 3 O 4 catalysts was studied by Raman and XPS techniques. It was disclosed that the distribution of Fe 2+ and Fe 3+ in Fe 3 O 4 has an effect on Cu–Fe 3 O 4 interaction and catalyst surface basicity . Compared to CFO-PVA, CFO-CA has a larger amount of Fe 3+ , which mostly sits at the octahedral sites, leading to stronger Cu–Fe 3 O 4 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 CO 2 desorption are promoted as reflected in the lower E a and higher catalytic activity of CFO-CA.