Enhanced Surface Charge Localization Over Nitrogen-Doped In₂O₃ for CO₂ Hydrogenation to Methanol with Improved Stability

Abstract

Indium oxide (In 2 O 3 ) is active and promising for selective hydrogenation of CO 2 to methanol. However, it suffers from over-reduction at elevated temperatures, causing deactivation. Herein, a nitrogen-doped In 2 O 3 (N−In 2 O 3 ) catalyst was prepared using a plasma-intensified nitrogen-doping technology. It is confirmed that nitrogen doping is effective for the stabilization of In 2 O 3 . The doped nitrogen enhances the surface charge localization, which inhibits the over-reduction on the oxide surface and limits the generation of excessive surface oxygen vacancies. The doped nitrogen also serves as the active site, synergistically with surface oxygen vacancy, which leads to an enhanced dissociation of CO 2 to adsorbed CO* intermediates. The electron-rich nitrogen causes a strong adsorption of CO on N−In 2 O 3 and inhibits the formation of free CO. A significantly improved methanol selectivity with a higher turnover frequency (TOF) is thus achieved on N− In 2 O 3 , compared to the un-doped In 2 O 3 . For example, at 21,000 cm 3 h −1 g cat −1 , 300 °C, and 5 MPa, the TOF of N−In 2 O 3 reaches 37.0 h −1 with methanol selectivity of 75.1%, while the TOF of the un-doped In 2 O 3 is only 16.0 h −1 with methanol selectivity of 62.3%. Different from pristine In 2 O 3 , N−In 2 O 3 takes the CO hydrogenation route for CO 2 hydrogenation to methanol. This explains the reason why the N−In 2 O 3 catalyst possesses improved selectivity for CO 2 hydrogenation to methanol.

Screened Fe3 and Ru3 Single-Cluster Catalysts Anchored on MoS2 Supports for Selective Hydrogenation of CO2

“…It can be concluded that the Fe 3 /MoS 2−v catalyst exhibits significantly higher TOFs of CH 3 OH production than CH 4 formation at all temperature and pressure ranges. Specifically, the TOF of CH 3 OH formation on Fe 3 /MoS 2−v at 4 MPa and 523 K can achieve 1.6 × 10 −4 s −1 site −1 , close to the experimental TOF values of metal oxide catalysts,53,54 while the TOF of CH 4 on this site is only 1.3 × 10 −11 s −1 site −1 . By calculating the degree of rate control (DRC) of reaction intermediates and transition states (FigureS8),55 we find that the removal of the hydroxyl intermediate and *H 2 COO hydrogenation is vital to the overall reaction rate.…”

yIn2O3-ZnZrOx/Hierarchical ZSM-5 Tandem Catalysts for CO2 Hydrogenation to Aromatics Rich in Tetramethylbenzene

“…These results were in agreement with the CO 2 -TPD results that the temperature of CO 2 desorption peak at higher temperature shifted from 568 °C for ZnZrO x to 619 °C for 10In 2 O 3 -ZnZrO x . Therefore, compared with the formed oxygen vacancies on ZnZrO x by the doping of Zn atoms into ZrO 2 , 10In 2 O 3 -ZnZrO x not only possessed more oxygen vacancies (Figure (d) and Table ) due to the formation of defect on In 2 O 3 lattice and partial reduction of In 2 O 3 under reaction conditions but also enhanced the adsorption and activation ability of CO 2 , which will increase reaction activity of CO 2 during its hydrogenation conversion process.…”

CO2 Hydrogenation to Methanol over In2O3: The Size Effect

“…As shown in panels a–c of Figure , the O 1s peak includes three peaks on all of the In 2 O 3 catalysts. These peaks located at 529.6, 530.9, and 531.8 eV are assigned to lattice oxygen (O lattice ), defective oxygen sites (O defect ), and hydroxyl groups (OH) absorbed on the surface (i.e., H 2 O and CH 3 OH), respectively . To further study the evolution of the surface oxygen vacancies, their relative concentration was calculated by C Odefect = A Odefect /( A Odefect + A Olattice ). , The results are shown in Figure d.…”