Preferential Oxidation of CO in H 2 on Pure Co 3 O 4− x and Pt/Co 3 O 4− x

Driven by the development of a catalyst made of earth‐abundant elements for on‐board purification of H 2 of this energy conversion technology, preferential oxidation (PROX) on pure Co 3 O 4 nanorods and Co 3 O 4 nanorods with supported Pt nanoparticles was explored with the aid of in situ studies. This catalyst remains its 100 % conversion of CO in H 2 at a gas hourly space velocity of 42 857 mL h −1  g −1 at 120 °C for at least 96 h. In situ studies showed that the active surface phase during PROX is nonstoichiometric Co 3 O 4− x . A correlation between density of surface oxygen vacancies and conversion of CO to CO 2 suggest that oxygen vacancy is a necessary component of a catalytic site for PROX on Co 3 O 4− x . Compared to pure Co 3 O 4 nanorods, anchoring Pt nanoparticles on Co 3 O 4 nanorods unfortunately increases selectivity for oxidation of H 2 owing to the low dissociation barrier of molecular H 2 on Pt. Co 3 O 4− x exhibits much higher selectivity for CO oxidation in PROX than Pt/Co 3 O 4− x at a temperature lower than 140 °C.