Based on the results presented so far, the effects of Rh oxide(s) on the catalytic performance of Rh-modified Ni-poly are very prominent. These are seen in HER catalysis as well as ORR catalysis, while the nature of the oxides present on the surface is crucial for OER catalysis. Based on Ref. , Rh forms two high-valence oxides at high potentials, Rh2O3 (above 0.9 V, orthorhombic phase), and RhO2 (above 1.75 V, tetragonal phase). These thermodynamic data should be complemented by kinetic data for oxide formation and especially reduction, which is evidently very slow, and significantly impacts the ORR kinetics and the hysteresis between anodic and cathodic scans. Moreover, recently, the formation of Rh2O3 and RhO2 was observed even during the electrodeposition of Rh-Ni alloys, while the oxides remained present during extended cycling in the HOR potential region (in alkaline media) . Based on the DFT calculations we have performed on bulk Rh2O3 and RhO2 (Figure ), Rh2O3 is a semiconductor, with a bandgap of 0.51 eV. This bandgap is underestimated due to the methodology used, while a previous DFT+U study (U = 3.5 eV) indicated a bandgap of 1.14 eV . Moreover, experimentally it was found that Rh2O3 has a direct band gap of 3.4 eV and an indirect band gap of 1.22 eV. On the other hand, higher-valence oxide, RhO2, is a conductor (Figure ). Thus, we believe that under ORR conditions, the Rh phase of the Rh-modified Nipoly is converted to semiconducting Rh2O3, which impedes ORR. Additionally, the Rh surface is highly oxophilic leading to its low predicted ORR activity . As Rh2O3 is reduced very slowly, it is also likely to be present to a low extent under the HOR condition, also impeding the rate of this reaction.