Assembly of crosslinked oxo-cyanoruthenate and zirconium oxide bilayers: Application in electrocatalytic films based on organically modified silica with templated pores

Abstract

Electrochemical deposition of crosslinked oxo-cyanoruthenate, Ru-O/CN-O, from a mixture of RuCl3 and K4Ru(CN)6 is known to yield a film on glassy carbon that promotes oxidations by a combination of electron and oxygen transfer. Layer-by-layer (LbL) deposition of this species and of a film formed by cycling of the electrode potential in a ZrO2 solution systematically increases the number of catalytically active sites of the Ru-O/CN-O on the electrode. The evaluation of the electrocatalytic activity was by cyclic voltammetric oxidation of cysteine at pH 2. Plots of the anodic peak current vs. the square root of scan rate were indicative of linear diffusion control of this oxidation, even in the absence of ZrO2, but the slopes of these linear plots increased with bilayer number, n, of (ZrO2 | Ru-O/CN-O)n. The latter observation is hypothesized to be due to an increased number of active sites for a given geometric electrode area, but proof required further study. To optimize utilization of the catalyst and to provide a size-exclusion characteristic to the electrode, the study was extended to LbL deposition of the composite in 50-nm pores of an organically modified silica film deposited by electrochemically assisted sol-gel processing using surface-bound poly(styrene sulfonate) nanospheres as a templating agent.

Electroanalysis based on stand-alone matrices and electrode-modifying films with silica sol-gel frameworks: a review

“…In addition, transmission electron spectroscopy of a cross-section of the ormosil film gave images in agreement with the model [33]. Further evidence of the cylindrical shape was obtained by layer-by-layer assembly of RuOCN and ZrO 2 in 50-nm pores [36] where RuOCN is mixed-valent ruthenium oxide with oxycyano crosslinks that is electrochemically synthesized by cyclic voltammetry of a K 4 Ru(CN) 6 , RuCl 3 mixture [42]. The current increased in direct proportion to the number of layers, which signifies a cross-sectional area that is independent of the vertical position along the pore, i.e., the areas of the pore cross-sections are independent of their position along the length of the pore.…”

“…A more direct test of the above hypothesis was by depositing the film on an electrode that was pretreated by binding a sub-monolayer distribution of PSS nanobeads to its surface [32,33,36,37]. Initially, a sub-monolayer of APTES was adsorbed.…”

Immobilization of nanobeads on a surface to control the size, shape, and distribution of pores in electrochemically generated sol–gel films

“…That is, the data suggested, first, that the pore shape was a “shadow” of the surface-bound species rather than a deposit around the exterior surface of the PSS spheres and, second, that the sol-gel phase was sufficiently compact to block mass transport of electroactive species from the solution to the electrode surface by paths other than through the templated pores. In a further extension of our previous studies [27, 29], a systematic evaluation of the influence of APTES on the density of the pores was made in this investigation.…”

Electrogeneration of non-electroactive and non-conducting materials: a counterintuitive concept for the functionalization and nanostructuration of electrode surfaces

“…This enables to avoid leaching of the organo-functional groups, as common for other types of sol-gel materials [212][213][214][215], thanks to the non-hydrolysable metal-carbon bond in metal alkoxides [216]. The organo-functional groups are selected for their particular properties, promoting tailor made features to the hybrid films, such as preconcentration ability [80,165,217], molecular recognition [209,218], ion exchange [219,220], electrocatalysis [221,222], selective permeation [61,157,223,224], superhydrophobicity [225][226][227] or protection against corrosion [227][228][229]. • Seventhly, combining the electro-assisted sol-gel formation with the inclusion of a surfactant template enables to get highly ordered and nanostructured deposits (see, e.g., pioneering works for vertically aligned mesoporous silica films [230] or lamellar structured zinc oxide films [136]).…”