Effect of La on the Structure, Selectivity and Stability of La/Co3O4 Catalysts in Preferential Oxidation of Carbon Monoxide in Hydrogen-Rich Streams

The Co 3 O 4 -based catalyst was prepared via precipitation method, followed by lanthanum incorporation through incipient wetness impregnation. All catalysts were evaluated in the preferential oxidation (PROX) of carbon monoxide in hydrogen-rich streams. Catalysts were characterised using XRD, BET surface area, TGA, SEM, TEM, FTIR, TPR, and XPS. The XRD and FTIR results confirmed the formation of the spinel CO 3 O 4 phase. The TPR measurements suggest the formation of LaCo linkage, which evidences strong electronic and structural interaction between La species and the Co 3 O 4 lattice. An increase in the Co 3+ /Co 2+ ratio was observed over the catalyst loaded with 1 wt% La species. As a result, an improvement in PROX performance was observed for the 1 wt% La/Co 3 O 4 catalyst, which exhibited optimum activity at relatively lower temperatures (~60 to 120 °C). A slight decrease in CO conversion with time on stream was observed for 1wt.% La/Co 3 O 4 in the presence of moisture, attributable to La doping, which suppresses OH-vacancy-assisted dissociative adsorption of H 2 O. Furthermore, the introduction of CO 2 into the feed resulted in an approximately 30% decrease in catalytic activity with time on stream. Overall, La doped Co 3 O 4 appears as a promising catalyst for low temperature (~80–120 °C) CO reduction in hydrogen rich streams, aligning with requirements for efficient proton exchange membrane fuel cells.