Tunable Carbon Dioxide Activation Pathway over Iron Oxide Catalysts: Effects of Potassium
Pengfei Tian, Mengwei Gu, Runfa Qiu, Zixu Yang, Fuzhen Xuan, Minghui Zhu
Abstract
The activation of CO2 to form CO, known as the reverse water–gas shift (RWGS) reaction, is an initial and essential step of numerous CO2 hydrogenation reactions. However, the reaction is challenging, and the underlying CO2 activation mechanism is usually overlooked when designing new heterogeneous catalysts. In this work, we investigate the effect of potassium, a common alkali metal promoter, on the iron oxide catalysts using a series of (quasi) in situ characterization techniques, kinetic analysis, and first-principles calculations. It is revealed that introducing potassium increases the surface basicity and steers the preferred CO2 activation reaction route from a “redox” pathway to an “associative” pathway. Understanding the controlling factors and competitiveness of the two CO2 activation mechanisms can potentially benefit the rational design of CO2 hydrogenation catalysts.