Single phase of spinel Co₂RhO₄ nanotubes with remarkably enhanced catalytic performance for the oxygen evolution reaction

We report the effective crystal growth for a unique single phase of spinel cobalt rhodium oxide (Co₂RhO₄) nanotubes via the electrospinning process combined with the thermal annealing process. In the spinel structure of the electrospun Co₂RhO₄ nanotubes, Co³⁺ cations and Rh³⁺ cations randomly occupy the octahedral sites, while the remaining half of the Co²⁺ cations occupy the centres of the tetrahedral sites as proved by microscopic and spectroscopic observations. Furthermore, electrospun spinel Co₂RhO₄ nanotubes exhibit excellent catalytic performances with the least positive onset potential, greatest current density, and low Tafel slope which are even better than those of the commercial Ir/C electrocatalyst for the oxygen evolution reaction (OER) in alkaline solution. Our demonstration of significantly enhanced OER activity with a single phase of electrospun spinel Co₂RhO₄ nanotubes thus opens up the broad applicability of our synthetic methodology for accessing new OER catalysis.