The Effect of H2O and CO2 on the Adsorption Behavior of H2 and CO on Hematite

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.