Insights into the mechanism of electrochemical ozone production via water splitting on the Ni and Sb doped SnO 2 catalyst.

The H2 O splitting mechanism is a very attractive alternative used in electrochemistry for the formation of O3 . The most efficient catalysts employed for this reaction at room temperature are SnO2 -based, in particular the Ni/Sb-SnO2 catalyst. In order to investigate the H2 O splitting mechanism density functional theory (DFT) was performed on a Ni/Sb-SnO2 surface with oxygen vacancies. By calculating different SnO2 facets, the (110) facet was deemed most stable, and further doped with Sb and Ni. On this surface, the H2 O splitting mechanism was modelled paying particular attention to the final two steps, the formation of O2 and O3 . Previous studies on β-PbO2 have shown that the final step in the reaction (the formation of O3 ) occurs via an Eley-Rideal style interaction where surface O2 desorbs before attacking surface O to form O3 . It is revealed that for Ni/Sb-SnO2 , although the overall reaction is the same the surface mechanism is different. The formation of O3 is found to occur through a Langmuir-Hinshelwood mechanism as opposed to the Eley-Rideal mechanism. In addition to this the relevant adsorption energies (Eads ), Gibb's free energy (ΔGrxn ) and activation barriers (Eact ) for the final two steps modelled in the gas phase have been shown, providing the basis for a tool to develop new materials with higher current efficiencies.