The Effect of H<sub>2</sub>O and CO<sub>2</sub> on the Adsorption Behavior of H<sub>2</sub> and CO on Hematite.

Abstract

The adsorption of gas reactant molecules (H₂, CO, etc.) to the surface of hematite is the premise of chemical reaction. In order to further promote the basic research on the reaction mechanism of hematite reduction by a H₂-CO gas mixture, the adsorption behavior of H₂ (or CO) under the conditions of pre-adsorbed H₂O (or CO₂) was systematically studied by the density functional theory (DFT) combined with reduction experiments. The results indicate that the gas molecules (H₂, CO, H₂O and CO₂) adsorbed on the Fe atom of the Fe₂O₃ (001) surface rather than the O atom, and the adsorption energy of the Fe₂O₃-CO adsorption system was relatively minimum (-1.317 eV), indicating that the Fe₂O₃-CO adsorption system was more stable. In addition, the adsorption energy of the H₂ molecule adsorbed to the Fe₂O₃-H₂O adsorption system was -0.132 eV, which was smaller than that of the H₂ molecule directly adsorbed to Fe₂O₃ (-0.013 eV), indicating that the H₂O molecule pre-adsorption was beneficial to the H₂ molecule adsorption. Compared with the H₂O molecule, the CO₂ molecule had relatively less influence on the adsorption and subsequent behavior of CO with Fe₂O₃. From the experiment analysis results, on the whole, CO₂ had a greater impact on the gas diffusion, while H₂O had a greater impact on the interfacial chemical reaction (gas adsorption), which was consistent with the DFT calculation results.