Trace CO elimination in H2-rich streams with a wide operation temperature window: Co deposited CuO–CeO2 catalysts

Abstract

This work provides a new strategy to eliminate trace CO in H₂-rich gas in a wide operation temperature window for the application of hydrogen fuel cells. We engineered Co deposited CuO–CeO₂ catalysts with a Co/(Cu + Ce) molar ratio of 1/1 that manages to maintain the CO level at below 100 ppm from 85 to 240 °C in the H₂-rich reformate stream. CO-PROX and CO methanation reaction respectively occurred in the low and high temperature ranges. Multiple characterization techniques demonstrate that the molar ratio of Co/(Cu + Ce) significantly affects the synergistic interactions between the Cu, Co and Ce species, and ultimately the CO oxidation and CO methanation reactions. At low reaction temperatures, the Cu–Ce interaction mainly dominates the CO-PROX process, while at high reaction temperatures, CO methanation reaction takes place due to the reduction of Co₃O₄ to Co⁰ and the Co–Ce interaction takes charge of the CO methanation. Moreover, the increment of Co/(Cu + Ce) from 1/2 to 1 gives rise to the reprecipitation of the partially dissolved Cu species on Co₃O₄, which strengthens the Cu–Co interaction and stabilizes surface Cu⁺ and Co³⁺, thus promoting the low temperature CO-PROX catalytic performance.