Evaluating Differential Electrochemical Mass Spectrometry as a Tool to Probe the Lattice Oxygen Exchange Mechanism of Oxygen Evolution at Transition Metal Oxide Catalysts
Christoph J. Bondue, Biao He, Pouya Hosseini, Gabriel Boitel-Aullen, Tong Li, Kristina Tschulik
It is often assumed that oxygen evolution at transition metal oxide electrodes proceeds via a mechanism in which the lattice oxygen of the catalyst is partially oxidized to O2. The formed vacancy in the anion lattice is then filled with oxygen originating from the water of the electrolyte. To prove this mechanism, oxygen evolution from isotopically labelled electrolytes featuring H218O is typically monitored via differential electrochemical mass spectrometry. If these experiments show that the mol fraction of 16O18O in the formed oxygen deviates from the expected value, the lattice exchange mechanism is considered proven. In our new article, we evaluate this methodology and point out how experimental pitfalls can be avoided. Moreover, we show for the first time how experimental data can be evaluated quantitatively to extract information about the fraction of oxygen that is evolved via the lattice oxygen exchange mechanism.