Mechanism of highly selective low temperature PROX reaction of CO in H2: Oxidation of CO via HCOO with OH

Oxidation of CO is markedly enhanced by H2 and/or H2O on FeOx loaded Pt/TiO2 (FeOx/Pt/TiO2) catalyst. Similarly, oxidation of CO on the Pt/CNT and Pt/CNF was enhanced by H2 and/or H2O. As a result, highly selective preferential oxidation (PROX) of CO is established at low temperature on these catalysts. The oxidation of CO on these catalysts has a hydrogen isotope effect by H2O/D2O and H2/D2, which suggests the intermediate at the rate determining step involves hydrogen atom. Dynamics of in situ DRIFT spectroscopy on FeOx/Pt/TiO2 suggests that the rate determining step of the PROX reaction of CO is the oxidation of HCOO with OH. TEM image proves that Pt particles are on the outer wall of the CNT but Ni–MgO and FeOx are localized at the end of CNT and CNF. If Ni–MgO and Fe in CNT and CNF were removed (CNT-p and CNF-p), the Pt lost the activity for low temperature PROX reaction of CO. Characteristic feature of the PROX reaction suggests a dual functional catalysis involving ionic process of CO + OH− → HCOO−, which is responsible for the low temperature PROX reaction of CO.