Active pairs of Cu0/Cu+ for CO2 hydrogenation

Copper (Cu) based catalysts are frequently used in CO 2 hydrogenation, particularly in reverse water-gas shift (rWGS) and CO 2 -to-methanol reaction. Cu 0 and Cu  +  are the key species affecting the catalyst performance and product distribution . Therefore, constructing and adjusting Cu 0 /Cu + active pairs is significant for the catalyst design . In this study, Cu 0 /Cu + active pairs are obtained by utilizing the properties of perovskite-type oxides (PTOs). A series of CaTi 1-x Cu x O 3 and Ca 0.8 La 0.2 Ti 1-x Cu x O 3 (x = 0.05, 0.10, 0.15, 0.30, 0.40 and 0.50) were synthesized via citric acid complexing method and part of the Cu species entered the PTOs lattice. After reduction, large Cu particles and highly-dispersed Cu clusters were obtained simultaneously. The dispersed Cu clusters have more interfaces with the PTOs and provide abundant Cu  +  while large Cu particles tend to aggregate and supply mainly Cu 0 . Cu 0 activates H 2 and CO 2 and plays a vital role in the rWGS reaction . Cu + is the active site for methanol synthesis and it can strongly absorb CO. The ratio of Cu 0 /Cu  +  varies with different Cu content and doping La can also adjust the chemical state of surface Cu. The performance test demonstrates that both excessively high and low Cu 0 /Cu + ratios are beneficial for CO generation, while a moderate ratio is suitable for methanol synthesis . These insights provide a method for regulating the chemical state of surface metal species and help the catalyst design for CO 2 hydrogenation.