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Dimensionally stable anodes of titanium (Ti) metal coated with mixed metal oxides (MMO) are widely used in several electrochemical applications, especially chloro-alkali electrolysis. Herein, we deposited MMO coatings on Ti substrates in different compositions, namely, (60%RuO2-40%TiO2), (60%RuO2-30%TiO2-10%IrO2), and (60%RuO2-20%TiO2-15%IrO2-5%Ta2O5), where RuO2 has the same percentage ratio in all coatings. The aim was to use these electrodes for chlorine evolution reaction (CER) and oxygen evolution reaction (OER) applications. Electrochemical characterization of the coated samples was performed to identify the best Ti/MMO electrodes with the highest efficiencies among the various prepared combinations. The role of IrO2 and Ta2O5 in enhancing corrosion resistance and electrochemical efficacy was up for debate. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were exploited to determine the surface morphology, chemical composition, crystallinity, surface composition, and chemical states of the acquired coatings. The differential scanning calorimetry (DSC) method was used to evaluate the apparent activation energy ( E a ) of the deposited MMO. Additionally, the electrochemical performance of our designed coatings was scrutinized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), a current on–off test, a CV stability test (ST), and an accelerated stability test (AST). Furthermore, linear sweep voltammetry (LSV) was incorporated to assess the catalytic efficacy of the prepared anodes toward the CER in a brine solution of pH 2 and the OER in 1 M H2SO4. It became clear that the CER and OER incurred almost the same potential value (1.1 V) on both Ti/RuO2-TiO2 and Ti/RuO2-TiO2-IrO2 electrodes. However, on the Ti/RuO2-TiO2-IrO2-Ta2O5 anode, there was a 0.2 V potential difference between the CER occurring at 1.1 V and the OER happening at 1.3 V. [ABSTRACT FROM AUTHOR]

Chlorine (Cl2) is one of the most important chemicals produced by the electrolysis of brine solutions and is a key raw material for many areas of industrial chemistry. For nearly half a century, dimensionally stable anode (DSA) made from a mixture of RuO2 and TiO2 solid oxides coated on Ti substrate has been the most widely used electrode for chlorine evolution reaction (CER). In harsh operating environments, the stability of DSAs remains a major challenge greatly affecting their lifetime. The deactivation of DSAs significantly increases the cost of the chlor-alkali industry due to the corrosion of Ru and the formation of the passivation layer TiO2. Therefore, it is urgent to develop catalysts with higher activity and stability, which requires a thorough understanding of the deactivation mechanism of DSA catalysts. This paper reviews existing references on the deactivation mechanisms of DSA catalysts, including both experimental and theoretical studies. Studies on how CER selectivity affects electrode stability are also discussed. Furthermore, studies on the effects of the preparation process, elemental composition, and surface/interface structures on the DSA stability and corresponding improvement strategies are summarized. The development of other non-DSA-type catalysts with comparable stability is also reviewed, and future opportunities in this exciting field are also outlined. [ABSTRACT FROM AUTHOR]

The chlorine evolution reaction (CER) and oxygen evolution reaction (OER) occur simultaneously due to the low difference (0.13 V) in their standard potentials. RuO2 is the state‐of‐art electrocatalyst used for both OER and CER. The activity and selectivity of different RuO2 low‐index facets, namely (100), (110), (111), (001) and (101), are investigated through ab‐initio density functional theory (DFT) based calculations. The selectivity of different facets is explored in a mixed OER‐CER region by combining Pourbaix diagrams and linear scaling relationships. The difference in limiting overpotential of OER and CER is identified as the selectivity descriptor (SDCER). The most CER‐ and OER‐selective facets are found to be (101) (SDCER=0.39 V) and (001) (SDCER=0.14 V), respectively. The understanding of facet dependent CER selectivity in RuO2 can be extended as a design strategy to modulate OER and CER activity and selectivity as per design requirements. [ABSTRACT FROM AUTHOR]