Dynamic Characterization of the Intermediates for Low-Temperature PROX Reaction of CO in H2—Oxidation of CO with OH via HCOO Intermediate

Abstract

The preferential oxidation (PROX) reaction of CO (CO + H2 + 1/2O2 → CO2) on a FeOx/Pt/TiO2 catalyst (∼140 wt % FeOx on 1 wt % Pt/TiO2) was studied at 60 °C by using in situ DRIFT spectroscopy. The PROX reaction of CO occurs via a HCOO intermediate and its oxidation with OH instead of oxygen, which is different from ordinary oxidation of CO with O2 (CO + 1/2O2 → CO2). The mechanism is as follows: (i) CO(a) + OH− → HCOO + e, (ii) O + e + H+ → OH, and (iii) HCOO + OH → CO2 + H2O, and step (iii) is the rate-determining step. Providing HCOO intermediates by a reaction of CO(a) with the OH− anion, step (i), was deduced by combining an electroconductive PROX catalyst (Pt/CNT(carbon nanotube)) with a hydrogen fuel cell. The oxidation of CO enhanced by H2 and H2O and the hydrogen isotope effect by H2/D2 and H2O/D2O on the FeOx/Pt/TiO2 catalyst are well explained by this mechanism.