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

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.