Sulfate residuals on Ru catalysts switch CO reduction from methanation to reverse water-gas shift reaction.

Efficient heterogeneous catalyst design primarily focuses on engineering the active sites or supports, often neglecting the impact of trace impurities on catalytic performance. Herein, we demonstrate that even trace amounts of sulfate (SO) residuals on Ru/TiO can totally change the CO reduction from methanation to reverse-water gas shift (RWGS) reaction under atmospheric pressure. We reveal that air annealing causes the trace amount of SO to migrate from TiO to Ru/TiO interface, leading to the significant changes in product selectivity from CH to CO. Detailed characterizations and DFT calculations show that the sulfate at Ru/TiO interface notably enhances the H transfer from Ru particles to the TiO support, weakening the CO intermediate activation on Ru particles and inhibiting the further hydrogenation of CO to CH. This discovery highlights the vital role of trace impurities in CO hydrogenation reaction, and also provides broad implications for the design and development of more efficient and selective heterogeneous catalysts.