Abstract:

The green and energy-efficient water splitting reaction using electrocatalysis for O₃ formation provides a very attractive alternative to the conventional energy-intensive cold corona discharge (CCD) method. Among a large number of electrocatalysts explored for the electrochemical ozone production, β-PbO₂ and SnO₂-based catalysts have proven to be the most efficient ones at room temperature. In this study Density Functional Theory (DFT) calculations have been employed to investigate the possible mechanisms of ozone formation over these two types of catalysts. For both the β-PbO₂ and Ni/Sb-SnO₂ (nickel and antimony doped tin oxide) catalysts the (110) facet was found to be the most stable one. The possible water splitting mechanisms were modeled on both the β-PbO₂(110) and Ni/Sb-SnO₂(110) surfaces with particular attention given to the final two reaction steps, the formations of O₂ and O₃. For the β-PbO₂, the formation of O₃ was found to occur through an Eley-Rideal style mechanism as opposed to that on the Ni/Sb-SnO₂, the latter occurs through a Langmuir-Hinshelwood style interaction. Thermodynamic parameters such as the adsorption energies (E_ads), Gibbs free energies (ΔG) and activation energies (E_act) have also been obtained, compared and presented, with β-PbO₂ being modelled primarily as solid-liquid phases and Ni/Sb-SnO₂ modelled as gas phase. These DFT findings have provided the basis for a tool to design and develop new electrochemical ozone generation catalysts capable of higher current efficiencies.

Key words: ozone evolution reaction, water splitting, density functional theory, electrocatalysis, surface adsorption and reaction, lead oxide, nickel and antimony doped tin oxide