Highly porous single-phase rhombohedral Cr_xRh_2−xO₃ nanofibers expediting oxygen evolution reaction

Single-phase rhombohedral Cr_xRh_2−xO₃ nanofibers are demonstrated as an excellent and stable electrocatalyst for oxygen evolution reaction (OER) under alkaline condition. Facile optimization of the annealing temperature for electrospun nanofibers composed of Cr/Rh metal precursors and poly(vinylpyrrolidone) could produce highly porous nanofibers of single-phase Cr_xRh_2−xO₃ by randomly distributing two metal ions of Cr³⁺ and Rh³⁺ in the rhombohedral crystalline lattice sites. Single-phase Cr_xRh_2−xO₃ could then induce the best synergistic effect of Cr and Rh owing to the perturbation of the surface electronic structure of the electrocatalyst active site and much enlarged electroactive surface area. Density functional theory (DFT) simulation integrated with experimental data indicated that the increased activity was due to moderate d-band center energy levels. This regulates oxygen desorption and adsorption capacities in the intermediates (*OH, *O, and *OOH). Conclusively, Cr_xRh_2−xO₃ nanofibers exhibited superior OER catalytic performances (low overpotential and Tafel slope with high stability and easy product desorption) compared to other Rh-related catalysts reported to date.