Green synthesis and characterization of binary, ternary, and quaternary Ti/MMO anodes for chlorine and oxygen evolution reactions

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 ( \({{\text{E}}}_{{\text{a}}}\) ${\text{E}}_{\text{a}}$ ) 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.