Structural, Morphological, and Electrocatalytic Activity of GdMn0.5M0.5O3 (M = Cr, Fe, Co) Perovskites

Abstract

GdMn0.5M0.5O3 (M = Cr, Fe, Co) perovskites were synthesized by a glycine‐assisted solution combustion method. Phase formation and crystal structure were investigated by powder x‐ray diffraction, and Rietveld refinement confirmed single‐phase orthorhombic perovskites (space group Pnma). Refined structural parameters were used to evaluate several crystallochemical distortion indices, including the global instability index. Far‐infrared spectroscopy confirmed the perovskite framework through characteristic Gd─O and Mn/M─O vibrational modes, while band splitting and frequency shifts indicated octahedral distortions. Microstructural evolution was examined by scanning electron microscopy and energy‐dispersive x‐ray spectroscopy following sequential annealing at 800°C for 8 h and 900°C for 4 h. After the first step, all samples exhibited a highly porous, interconnected morphology typical of combustion‐synthesized powders. The second heat treatment promoted partial densification, grain growth, and improved interparticle connectivity, leading to a more homogeneous and structurally stable microstructure. Elemental mapping confirmed uniform cation distribution and compositions close to the nominal stoichiometry. Electrocatalytic performance was evaluated by cyclic voltammetry using paraffin‐impregnated graphite electrodes modified with perovskite microcrystals. The electrochemical response toward hydroxide oxidation and the hydrogen evolution reaction depended strongly on the B‐site composition, with GdMn0.5Co0.5O3 exhibiting the highest catalytic activity while maintaining good electrochemical stability during repeated cycling.