Zn-Doped RuO₂ electrocatalyts for Selective Oxygen Evolution: Relationship between Local Structure and Electrocatalytic Behavior in Chloride Containing Media

Abstract

Nanocrystalline electrocatalytically active materials of chemical composition Ru 1-x Zn x O 2 (0< x < 0.3) were synthesized by freeze-drying technique. The diffraction patterns of the prepared samples corresponded to single-phase rutile type oxides. Local structure of the Ru 1-x Zn x O 2 based on refinement of Ru K and Zn K edge EXAFS functions shows clustering of the Zn ions in the blocks with ilmenite structure intergrowing with Ru-rich rutile blocks. Ru 1-x Zn x O 2 oxides are selective catalysts for anodic oxygen evolution. The selectivity toward oxygen evolution in the presence of chlorides is affected by the actual Zn content and can be ascribed to structural hindrance of the formation of the surface peroxo group based active sites for chlorine evolution. The selectivity toward oxygen evolution in presence of chlorides is accompanied by the drop of the total activity, which gets more pronounced with increasing Zn content.

Roughened Zn‐Doped Ru–Ti Oxide Water Oxidation Electrocatalysts by Blending Active and Activated Passive Components

“…In this regard, the mechanisms by which Zn and Ti increase activity in the ternary RuO 2 based electrocatalysts seem to be different. In the co‐electrodeposited RuZn electrode, the presence of Zn atoms in the subsurface region causes distortion of the local surface structure of RuO 2 , which lowers the activation energy for electrocatalytic water oxidation, as suggested by DFT studies . Tafel‐slope analysis and the higher exchange‐current density of the Zn‐doped RuO 2 catalyst in comparison to the RuO 2 catalyst also support this hypothesis.…”

“…From this we infer that most of the Zn is present in the subsurface region. Previous DFT studies indicated that subsurface Zn is responsible for lowering the activation energy of the OER . Furthermore, Ru 0.258 Ti 0.736 Zn 0.006 O x and Ru 0.33 Ti 0.67 O x have nearly equal amounts of Ru and Ti atoms on the surface.…”

“…An alternative strategy to increase the activity and stability of RuO 2 is doping with Ta, Ce, Co, Ni, or Nb. However, the extent of doping is restricted by the limited solubility of the dopant in the host rutile oxide …”

Integrated Valorization of Desalination Brine through NaOH Recovery: Opportunities and Challenges

“…[57] Indeed, CER is typically favored over OER at acidic conditions. [62,63] More recent work used similar doped manganese oxides [52,64] and other doped oxides [59,61,65] to selectively produce oxygen even under acidic brine conditions with reasonable selectivity. [57,[59][60][61] Oxygen-selective catalysts in acidic chlorinated conditions are relatively underexplored, yet afew promising early studies have reported selectivity for oxygen production from seawater by using doped manganese oxides.…”

“…Reprinted from ref [65]. For10% Zn, oxygen is selectively formed over chlorine gas at most potentials.…”