Electrochemical Properties of Ti/SnO₂-Sb-Ir Electrodes Doped with a Low Iridium Content for the Oxygen Evolution Reaction in an Acidic Environment

Abstract

Ti/SnO 2 -Sb-Ir electrodes doped with a low Ir content were prepared, and they were used in acidic water electrolysis for the oxygen evolution reaction (OER). The results showed that an IrO 2 −SnO 2 solid solution was formed, and the electrode surface was relatively compact. The doping of IrO 2 could significantly improve the electrocatalytic activity and stability of Ti/SnO 2 -Sb electrode for OER. The electrode modified with only 5 mol % Ir met the needs of acidic water electrolysis. Meanwhile, the performances of the electrode approached that of Ti/IrO 2 when Ir content was only 8 mol %, which resulted from the fact that IrO 2 doping improved the chemical stability as well as the electrocatalytic activity of the electrode. Moreover, the deactivation behavior of the electrode was investigated as well. It was mainly ascribed to the chemical composition and morphology change induced by continuous dissolution of the metal oxides, which eventually led to the passivation of the Ti substrate.

Preparation of Ti/IrRuSnSbOx Electrodes by a Hydrosol Process for Efficient and Stable Chlorine Evolution Reaction

“…The EDX results in Figure a show that the content of Sb greatly decreased or even almost disappeared with the increase of acid concentration. This was attributed to the excess acid inhibiting the hydrolysis of SbCl 3 and failing to prevent the sublimation of SbCl 3 during heating . In Figure b, the diffraction peaks of Ti and the solid solution peaks of Ir, Ru, Sn, and Sb were clearly identified.…”

“…The dissolution of metal oxides occurred in both electrodes, but the active substance in MMO A was dissolved quickly and eventually lost, while MMO H‑0.7 still retained some metal oxides. This indicated that a more stable solid solution structure effectively inhibited dissolution during electrolysis …”

“…Therefore, the reaction rate between metal salt and DI water was controlled by the concentration of HCl (0.7, 0.8, 0.9, and 1.0 M), which prevented Sb from precipitating. Finally, the precursor solution was used for repeated thermal decomposition for 10 times according to the synthesis temperature and other process parameters and operation methods in ref , and the total oxidation load was 1.0–1.3 mg/cm 2 . The electrode prepared by the alcohol method is named “MMO A ” and the electrode by the hydrosol method “MMO H‑ x ”, where x represents the concentration of HCl added.…”

“…At present, the performance and economy of electrodes are greatly improved by increasing the concentration of oxygen vacancy, changing the surface morphology and crystal structure, and facilitating the crystallization of IrO 2 . Mixed metal oxide (MMO) anodes have been constructed by mixing noble metal oxides (IrO 2 and RuO 2 ) with non-noble metal oxides such as Fe 2 O 3 , ZrO 2 , , CeO 2 , SnO 2 , , and Sb 2 O 5 . Among which, Sn–Sb codoping has emerged as a promising strategy, and the performance and application of Ti/IrSnSbO x and Ti/RuSnSbO x have also been studied extensively. − The Ti/IrRuSnSbO x electrode with a low noble metal content is a combination of the two, which has a lower chlorine evolution potential (1.11 V vs SCE) and a higher stability (68 h) and is regarded as a promising practical chlorine evolution anode.…”

“…In addition, the performance of electrodes can also be highly improved by changing the preparation process . In general, Sn–Sb codoped electrodes are prepared mainly by thermal decomposition of precursor chloride ,, and polymer precursors. , The homogeneity of precursor solution or the sol property is an essential factor affecting the performance of the electrode, which is related to the choice of aqueous or nonaqueous solvents of the precursor salt carrier. Since Sb hydrolyzes easily, nonaqueous solvents (typically C-3 or C-4 alcohols) are generally used to prevent hydrolysis, but solubility and stability of precursor salt are limited, and carbon tends to be introduced into the oxide coating .…”