Sn-based precursors dependence for electrocatalytic degradation of organic pollutants on Ti/SnO2-Sb electrode

Abstract

The utilization of SnO2-based coated electrodes prepared through thermal decomposition process for degrading organic pollutants is a prominent topic in the field of wastewater treatment. However, the impact of precursor salts on the structure and catalytic degradation activity of Sn oxide coatings still lacks research. This study examined the procedures for synthesizing SnO2 coatings by high-temperature oxidation of two common Sn chlorides with different valences. Through systematic characterization, it was revealed that the high boiling point of SnCl2 makes it less volatile during the high-temperature oxidation stage, allowing for maximum retention of Sn source on the substrate, thereby forming a dense and stable oxide coating structure (Ti/SnO2-Sb(II)). On the other hand, the low boiling point of SnCl4 makes it easily volatile during heating, resulting in a thin and loose structure coating (Ti/SnO2-Sb(IV)). Due to these factors that the electrical conductivity of Ti/SnO2-Sb(II) is significantly superior to Ti/SnO2-Sb(IV). Moreover, at 20 mA·cm−2, Ti/SnO2-Sb(II) can achieve almost complete decolorization of methylene Blue (MB) in just 40 minutes, while achieving the same decolorization rate with Ti/SnO2-Sb(IV) requires over 90 minutes. Furthermore, stability tests demonstrated that after 5 cycles of reaction, Ti/SnO2-Sb(II) showed no significant decrease in decolorization rate of MB, whereas Ti/SnO2-Sb(IV) exhibited a decline in decolorization performance towards MB starting from the 2nd cycle. This study revealed the crucial role of precursor salt boiling points in the formation of stable SnO2-based coated electrodes, providing a theoretical basis for the development of structurally stable and highly catalytic oxidation active coating electrodes.