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

The preferential oxidation (PROX) reaction of CO (CO + H 2 + 1 / 2 O 2 → CO 2 ) on a FeO x /Pt/TiO 2 catalyst (∼140 wt % FeO x on 1 wt % Pt/TiO 2 ) 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 O 2 (CO + 1 / 2 O 2 → CO 2 ). The mechanism is as follows: (i) CO(a) + OH − → HCOO + e, (ii) O + e + H + → OH, and (iii) HCOO + OH → CO 2 + H 2 O, 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 H 2 and H 2 O and the hydrogen isotope effect by H 2 /D 2 and H 2 O/D 2 O on the FeO x /Pt/TiO 2 catalyst are well explained by this mechanism.