Partial Exsolution-Generated Cu Nanoclusters on CuZrO ₂ Solid Solution Facilitate the Reverse Water Gas Shift Reaction

Cu-based catalysts are selective for the conversion of waste CO 2 to CO via reverse water gas shift (RWGS) reaction; however, they suffer from low activity and stability. Herein, Cu/ZrO 2 catalysts prepared by coprecipitation to form a solid solution, followed by Cu exsolution, were tested for RWGS at 400 °C. The highest intrinsic rate (160.7 mmol·g cat –1 ·h –1, 100% CO selectivity) was achieved on Cu/ZrO 2 -10 (precipitation pH value of 10), which was ∼4 times higher and much more stable than that of Cu/ZrO 2 - i (impregnation, 44.3 mmol·g cat –1 ·h –1 ). Characterizations demonstrated that the lower precipitation pH value led to a higher degree of CuZrO 2 solid solution, while a lower fraction of Cu was reduced and exsolved upon reduction with smaller Cu particle sizes. The highest activity of Cu/ZrO 2 -10 originates from the highest density of Cu/CuZrO 2 interfacial perimeter sites resulting from a combination of relatively high reduction degree of Cu species as well as small Cu particle size (2.6 nm). The similar E a (∼118 kJ·mol –1 ) and CO 2 orders (∼0.99) on Cu/ZrO 2 -10 and Cu/ZrO 2 - i suggest that the formation of intrinsic oxygen vacancies in CuZrO 2 has little effect on the adsorption and activation of CO 2 . The lower H 2 order of Cu/ZrO 2 -10 (0.55) than that of Cu/ZrO 2 - i (0.78) is due to the much smaller Cu size (2.6 vs 22.3 nm). The findings on the structure evolution of CuZrO 2 solid solution may be helpful for the rational design of active and stable Cu/ZrO 2 catalysts for RWGS.