Topography changes of rhodium electrodes induced by the application of fast periodic potential routines

Abstract

The surface structure of polycrystalline rhodium electrodes in contact with aqueous sulfuric acid was modified by chemical etching with hot concentrated acid or by applying fast square waves with an upper potential equal to 1.55 V and a lower potential within the -0.75 V to -0.35 V range. Polycrystalline rhodium and chemical etched electrodes were characterized by voltammetry, Cu underpotential deposition (upd) and X-ray diffraction. For electrofaceted surfaces were used voltammetry, Cu upd and SEM, revealing that two modified rhodium electrodes exhibit similar voltammetric characteristics as those found for Rh(111) and Rh(110) single crystals, and a third surface with an equal distribution of ( 110) and ( 111) planes. In addition, the upd of Cu on those surfaces corroborated the existence of those crystallographic planes. SEM micrographs show surface structures with a high density of terraces and steps. A mechanism of faceting is proposed.

Oxygen Reduction Reaction and Peroxide Generation on Ir, Rh, and their Selenides – A Comparison with Pt and RuSe

“…The Cu stripping on carbon-supported selenides of Ir, Rh, and Ru show somewhat different features. [42][43][44][45] It is interesting to note that Cu stripping is comparable on both RuSe and IrSe with featureless sharp peak that terminate at $ 0.6 V, and Cu stripping voltammogram on Rh exhibits crystallographic features even in presence of Se and it extends to $ 0.8 V (see Fig. 5c; a separate figure (Fig.…”

“…The role of Se in RuSe is to inhibit oxidation of Ru particles and to provide electronic effects for electrocatalysis. 15,17,44,49 In chalcogenides, the active catalytic center has been identified as metallic Ru. Chalcogens like Se in the catalyst prevents metallic Ru from forming Ru oxides thereby resulting in an enhanced ORR catalytic activity.…”

Restructuring of an Ir(210) electrode surface by potential cycling

“…The formation of facets by potential cycling has been extensively studied with platinum [ 27 – 32 ], rhodium [ 33 ] and gold surfaces [ 34 – 36 ]. Accordingly, the Ir(210) single crystal electrode was subjected to potential cycling at scan rates between 0.05 and 2 V·s −1 in 0.1 M H 2 SO 4 in the potential region between −0.28 to 0.7 V for different periods of time up to 4 h. In the following, we present results obtained with a scan rate of 1 V·s −1 , which show the most obvious effects.…”

Preparation and Electrochemical Behavior of Ordered Rh Adlayers on Pt(100) Electrodes

“…As mentioned in the Introduction section, a similar annealing procedure has been proposed for the faceting of spherical polyoriented single-crystal electrodes of different noble metals, and, in particular, of Rh. , However, in the latter case, the positive potential limit was either 1.20 or 1.55 V RHE , much higher than that employed here. Such positive potential limits are not applicable in our case because they would give rise to a disordering of the Pt(100) substrate.…”

“…Indeed, the positive potential limit employed both for Pt(100) and Rh/Pt(100) electrodes allows the adsorption/desorption of a significant coverage of oxygenated species. In the case of polyoriented Rh surfaces, , repetitive electrodissolution and electrocrystallization processes were suggested to be responsible for the faceting. In our case, this contribution does not seem to be so important because most of the Rh adatoms remain at the surface after the treatment.…”