Effect of oxygen vacancies in anodic titanium oxide films on the kinetics of the oxygen electrode reaction

Electronic properties of anodized TiO2 electrodes and the effect on in vitro response

“…The flat band potential is approximately the same while N d decreases slightly with increasing anodization current density. This is in agreement with previous findings where the number of charge carriers decreases with increasing growth rate . The capacitance values at the flat band potential are high and reflect rather the double layer capacitance than the dielectric properties of the oxide, Table .…”

“…The thickness of naturally formed titanium oxide on titanium was found to be about 3 nm in agreement with the expectations. However, the thickness of the anodized layers was much larger than reported in the literature for films formed under similar conditions . This is probably an artefact due to the amorphous character of the film.…”

“…A fast sweep rate leads to a more hydrated film with large dielectric constant but lower donor density, N d Also the flat band potential was shown to shift slightly negative with increasing growth rate . A sweep rate of 100 mV s −1 corresponds to an anodization current density of 0.5 mA cm −2,30 and also for galvanostatic anodization a decrease in N d with increasing current density, that is, with increasing growth rate has been observed . The current densities used in the present work corresponds to sweep rates larger than 200 mV s −1 where changes in the dielectric constant levels off and a value of about 95 can be expected …”

“…The influence of growth rate on the properties of the oxide has been studied previously both using potential sweeps with different sweep rates and galvanostatic anodization with different current densities . Because the growth process is field‐driven, the potential sweep technique is approximately equivalent with galvanostatic anodization.…”

Selective formation of hydrogen peroxide by oxygen reduction on TiO2 nanotubes in alkaline media

“…Obviously the addition of H 2 O 2 leads to the oxidation of Ti 3+ sites to Ti 4+ and reducing the number of oxygen vacancies[33] at the surface, which can explain the disappearance of oxygen reduction at the first peak at the TON-N 2 array. A study by Macdonald et al[34] looking at the effect of oxygen vacancies (donor density) in the anodic TiO 2 oxide film on the kinetics of the oxygen reduction reaction in acidic solution has shown that the presence of oxygen vacancies boosted the charge transfer and the rate of oxygen reduction was linearly depends on the oxygen vacancies density.This was attributed to the enhancement of the TiO 2 conductivity as well as the surface oxygen vacancies acting as catalytic sites for the oxygen reduction. The kinetic order of the reaction with respect to vacancies concentration found to be bigger than zero indicating the participation of the oxygen vacancies as catalytic sites.…”