Synthèse par co-précipitation des succinates, caractérisation, propriétés optiques et électrocatalytiques de l’oxyde de fer(iii) dopé au chrome.

Abstract

In this study, the potential of chromium-doped iron oxide as a material with enhanced electrocatalytic properties was explored. To achieve this, a series of metal succinates, precursors of the target materials, were synthesized and thermally decomposed. Two simple metal succinates, iron(III) succinate and chromium(III) succinate, as well as four mixed succinates, were prepared by a co-precipitation method in an alcoholic medium. The latter, with the general formula (CrₓFe₂₋ₓ(C₄H₄O₄)₃), exhibited different chromium concentrations (x = 0.04, 0.08, 0.11, and 0.13), thus allowing us to study the influence of doping on the final properties. To highlight the presence of these oxides in the decomposition products, the latter were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Spectroscopy (EDX). FTIR spectroscopy confirmed the presence of characteristic functional groups of metal succinates in the precursors, as well as metal–oxygen bonds in the oxides. XRD analysis revealed the formation of iron(III) oxide (Fe₂O₃), chromium(III) oxide (Cr₂O₃), and single- phase mixed Fe(III)–Cr(III) oxides (CrₓFe₂₋ₓO₃), thereby confirming the crystalline structure and purity of the obtained materials. Furthermore, SEM observations showed a decrease in the average particle size with increasing chromium content, suggesting an inhibitory effect on crystal growth due to the incorporation of chromium ions into the Fe₂O₃ lattice. EDX spectroscopy confirmed the chemical composition of the mixed oxides, revealing the presence of Fe, Cr, and O elements in expected proportions. The study of the optical properties by UV– Visible spectrophotometry revealed absorption in the 720–800 nm region, as well as a decrease in the band gap from 1.94 to 1.48 eV with chromium doping. This latter point is crucial, as the reduction in the band gap led to a significant improvement in the electrocatalytic properties of the materials. This advancement was reflected by a decrease in the overpotential at a current density of 10 mA cm⁻² (η₁₀) with increasing chromium doping levels in Fe₂O₃. In conclusion, this study successfully synthesized new mixed Fe(III)–Cr(III) oxides exhibiting promising electrocatalytic properties for addressing current energy challenges. The incorporation of chromium into iron oxide proved to be an effective strategy for tuning the electronic properties and enhancing the electrocatalytic performance of this material.