Structure and magnetism of electrospun porous high-entropy (Cr_1/5Mn_1/5Fe_1/5Co_1/5Ni_1/5)₃O₄, (Cr_1/5Mn_1/5Fe_1/5Co_1/5Zn_1/5)₃O₄ and (Cr_1/5Mn_1/5Fe_1/5Ni_1/5Zn_1/5)₃O₄ spinel oxide nanofibers

Abstract

The magnetism of electrospun porous high-entropy spinel oxides can be tuned by changing a single cation.

Evaluation of electrospun spinel-type high-entropy (Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)3O4, (Cr0.2Mn0.2Fe0.2Co0.2Zn0.2)3O4 and (Cr0.2Mn0.2Fe0.2Ni0.2Zn0.2)3O4 oxide nanofibers as electrocatalysts for oxygen evolution in alkaline medium

“…In agreement with a previous study, 61 the lattice parameter of the cubic cell, as inferred from Rietveld analysis (not shown for briefness), increases in the order CN-NFs (8.3215(8) Å) < NZ-NFs (8.3256(6) Å) < CZ-NFs (8.3712(8) Å). This trend is different with respect to that of the a -values estimated from HRTEM (NZ-NFs < CZ-NFs < CN-NFs).…”

“…S3, ESI†) prove that the oxide grains are crystalline; they have spinel structure and are randomly oriented. The lattice constants, as inferred from the geometrical phase analysis (GPA) of the crystal lattice fringes illustrated in detail in a previous paper, 61 increase in the order NZ-NFs (0.833 ± 0.003 nm) < CZ-NFs (0.836 ± 0.007 nm) < CN-NFs (0.843 ± 0.005 nm). This trend fully agrees with that reported for HEOs based on the same metal combinations synthesized by different method.…”

“…As a result, the HEO-NFs exhibit mostly a tube-like structure, as expected. 61,71 Previous studies on HEO-NFs produced under similar conditions have shown that their cross section, as resulting from the projection analysis of the EDX elemental maps, 61 varies with the TM combination. In particular, CN-NFs are quasi-solid (Fig.…”

“…22-1084), 73–77 indicating that pure single-phase solid solutions are formed in all samples, in full agreement with the evidences of the SAED analysis and the results of previous studies, as well. 57,61 The average size of the HEO crystallites, as calculated from the full width at half maximum (FWHM) of the most intense reflection through the Scherrer's equation, d = kλ / β cos θ (where k , λ , β and θ denote the shape factor, the wavelength of X-ray radiation, the FWHM in radians and the Bragg's angle, respectively), 78 decreases in the order CN-NPs (124 nm) > NZ-NFs (99 nm) > CN-NFs (97 nm) > CZ-NFs (84 nm).…”

“…57,58 Besides, in the case of ES, the oxide NFs formed upon calcination from the as-spun precursor templates typically consist of interconnected crystalline grains of small size. 58–61 As the NF-composing oxide particles that can be easily detached from each other by dissolution in a solvent under sonication, 59 they could be used in the preparation of nanoparticulate electrocatalytic inks. Hence, this work may lead to important advances in the field of both nanostructured and ink-jet printable electrocatalysts.…”