(667d) A Structural and Mechanistic Study of Electrochemical Ozone Production on Doped Tin Oxide Electrodes

Electrochemical ozone production (EOP) is a potential green alternative route for ozone (O₃) generation for advanced oxidation processes and water purification. Nickel and antimony doped tin oxide (NATO) is a promising EOP active catalyst due to its high selectivity and low toxicity. Currently, the mechanism of EOP on NATO electrodes is unclear. In addition, the role of dopants in inducing EOP activity in otherwise inactive tin oxide is not understood.

High EOP selectivity is fundamentally unexpected since the competing oxygen evolution reaction (OER) is thermodynamically favored due to its lower potential (1.23 for OER vs 1.51 V for EOP). EOP is usually assumed to be a surface-mediated reaction that proceeds parallel to OER. Many mechanisms, which attribute unique activities to different antimony and nickel species, have been suggested to explain the high reaction selectivity. However, direct experimental verification of proposed mechanisms has been challenging.

In this work, we build on previous reports to establish the mechanism of EOP on NATO electrodes. Previous studies showed that increasing the thickness of NATO electrodes increases selectivity and output, which suggested that non-surface bound intermediates play an active role in EOP. We further support this hypothesis using isotopic labeling and chemical ionization mass spectrometry. Our measurements demonstrate the participation of lattice oxygen in EOP and show that EOP is a non-surface bound reaction. We use x-ray photoelectron spectroscopy to explain the role of antimony in terms of its oxidation state. In addition, we study the structure of NATO electrodes using x-ray diffraction to understand the catalyst activity. We show that co-doping tin oxide with antimony and nickel generates unique active sites that are responsible for ozone activity Based on our findings, we predicted dopants with higher EOP performance and successfully synthesized improved doped tin oxide catalysts .