# Studies on the Electrochemical Behavior of Sulfite on Incoloy 800 in a Neutral Environment
## 1 Introduction
\[2\text{${}^{\bullet}$SO}_{3}\text{${}^{-}$}\rightarrow\text{S}_{2}\text{O}_{ 6}\text{${}^{2-}$} \tag{3}\]  
\[\text{S}_{2}\text{O}_{6}\text{${}^{2-}$}+2\text{OH${}^{-}$}\rightarrow\text{ SO}_{3}\text{${}^{2-}$}+\text{SO}_{4}\text{${}^{2-}$}+\text{H}_{2}\text{O} \tag{4}\]  
The oxidation of sulfite ions at high anode potentials has been attributed to a chemical reaction between oxygen adsorbed on the platinum surface and the oxygenated sulfur combination [28]. \[\text{O}_{\text{(ads)}}+\text{SO}_{2}+\text{H}_{2}\text{O}\rightarrow\text{H} _{2}\text{SO}_{4} \tag{5}\]  
The analysis of published data reveals that it is exceedingly difficult to obtain the conditions for anodic sulfite oxidation on a \"clean\" metal platinum. Only at anode potentials lower than those required to create the oxide layer can the oxidation process of the SO2/HSO3^-/SO3^2- compounds occur directly on the \"clean\" surface of the platinum [29]. On the gold anode, the oxidation pathway of the chemical species SO2/HSO3^-/SO3^2- is pH dependent. The cyclic voltammograms displayed in SO2/HSO3^-/SO3^2- solutions at pH levels ranging from 2 to 11 are cvasi-identic, indicating that the anodic process rate is practically constant. In this pH range, the anodic process involves the oxidation of sulfite to dithionate. In alkaline solutions (pH > 12.5), the voltammetric wave shifts to higher positive values, indicating that the anodic process involves the direct oxidation of sulfite to sulfate [30]. [PERSON] revealed that the kinetics of the anodic oxidation of sulfite on gold (0.1 M Na2 SO3 + 0.5 M Na2 SO4 solution) are affected by the metal surface's conditioning. The highest current on the electrode with the gold oxide coating removed was 0.8 V, while the maximum current on the oxidized anode was +0.6 V. The author demonstrated that, because the peak current at +0.8 V is greater than that at 0.6 V, sulfite adsorption occurs on the \"clean\" gold electrode by the direct creation of the Au-S bond [7]. The prices of the components of electrochemical reactors often limit the practical uses of these technologies. The electrode material plays a vital role here. In addition to catalytic activity, electrodes must withstand working circumstances such as corrosive electrolyte solutions, advanced anodic or cathodic polarization, polarization fluctuations, high temperatures, and so on. Platinum is a metal with excellent catalytic activity in a variety of electrochemical processes, including anodic and cathodic. Unfortunately, the price of platinum is exceedingly costly (about 37,600 USD/kg [31]), therefore, using platinum electrodes presents insurmountable economic challenges. Furthermore, the oxidation of the chemical species SO2/HSO3^-/SO3^2- affects the catalytic activity over time due to their adsorption on the platinum surface via the formation of Pt-S bonds. To address these challenges, the research focused on the usage of materials with low noble metal concentration. [PERSON] et al. electrochemically oxidized sulfite to sulfate in an alkaline atmosphere on a glossy nickel electrode, after which a coating of platinum nanoparticles was deposited using a spray-pyrolysis process using an ultrasonic nebulizer SONOTEK Corporation Exacta Coat. After deposition, the electrodes were heated to 350 ^C for 30 min to produce nano-sized platinum particles. Platinum nanoparticle deposition significantly accelerated the anodic oxidation of SO3^2- to SO4^2-[32]. The deposition of successive layers of nanoparticles improved the efficacy of the anodic process [33]. The use of a skeletonized nickel support accelerated the oxidation process from SO3^2- to SO4^2-[33; 34]. Composite anodes can also help to reduce the expenses of procuring electrodes. [PERSON] et al. developed a carbon-gold particle composite. anode (maximum 300 nm) for the anodic oxidation of sulfites in a very weak basic medium (pH = 8) [35]. [PERSON] et al.