Laser-Generated InO_x/ZrO₂ Catalysts for CO₂ Hydrogenation: Role of In Situ Fragmentation and Ripening Control

Abstract

It is desirable to reduce the reliance on fossil fuels and to develop alternative methods to yield valuable chemicals. CO2 hydrogenation to methanol is a promising approach, where In2O3/ZrO2 catalysts have attracted increasing attention due to their high selectivity and stability. However, the activity of indium-based catalysts is very susceptible to the preparation method, which is typically wet impregnation. Here, we explore a laser-based synthesis route to prepare InO x /ZrO2 catalysts of varying indium size and load. The respective particle sizes were either adjusted by in situ fragmentation with a more (ns-VIS-laser) or less (ns-IR-laser) efficient laser wavelength or by using micromolar concentrations of phosphate as an electrostatic stabilizer. The InO x colloids were subsequently deposited onto ZrO2 Our results demonstrate that the pulsed laser ablation with ns-IR-laser pulses yielded larger ∼45 nm crystalline cuboid InO x supported on zirconia. The frequency-doubled ns-VIS-pulses on the other hand caused an augmented in situ fragmentation during ablation, which led to catalysts with spherical ∼14 nm InO x particles with a significantly higher degree of amorphousness. Further size quenching and increased amorphous content of the InO x nanoparticles were observed when micromolar concentrations of phosphates were additionally present during ablation. After supporting the InO x nanoparticles onto ZrO2, the laser-generated catalysts were found to perform equally well as their wet-chemically prepared counterparts for methanol synthesis in a slurry phase, although crystalline In species performed slightly better in the catalytic reaction. In conclusion, in situ fragmentation does not only provide opportunities for independent studies of size and composition but also ripening control and structural modifications such as amorphization.

Indium‐based Catalysts for CO2 Hydrogenation to Methanol: Key Aspects for Catalytic Performance

“…The combination of In 2 O 3 and ZrO 2 as a support achieved a synergistic effect at the interface between oxygen vacancy defects of the oxides [17] . Adjusting the right particle size and morphology control are key factors for preparing Indium‐based catalysts with high activity [18] . The ZrO 2 carrier plays a crucial role in preventing the sintering of In 2 O 3 , thus ensuring long‐time‐stability of the catalyst.…”

“…[17] Adjusting the right particle size and morphology control are key factors for preparing Indium-based catalysts with high activity. [18] The ZrO 2 carrier plays a crucial role in preventing the sintering of In 2 O 3 , thus ensuring long-time-stability of the catalyst. According to proposed mechanisms, the oxygen vacancy filled after methanol desorption is regenerated through its hydrogenation by water formation.…”

Catalyst and Parameter Optimization Study for Slurry-Phase Methanol Synthesis Using Ni-Doped Indium-Based Catalysts

“…22 Nano-sized In 2 O 3 particles can be generated via laser ablation and deployed on ZrO 2 surfaces to tune the microstructure of the catalyst and to adjust the catalyst activity as well. 23 In industrial methanol synthesis, fixed-bed reactors are used. For example, Lurgi's MegaMethanol process uses pressures between 50 and 100 bar and reaction temperatures between 200 and 300 °C.…”

“…The integration of noble metals such as Pd and Ru, as well as non-noble metals like Ni, proved to further improve the catalytic activity. ,, The resulting hydrogen spillover effect leads to higher hydrogen availability on the catalyst surface wherein only a small amount of metal loading can boost the catalytic activity significantly . Nano-sized In 2 O 3 particles can be generated via laser ablation and deployed on ZrO 2 surfaces to tune the microstructure of the catalyst and to adjust the catalyst activity as well …”

The synergetic effect of Pd, In and Zr on the mechanism of Pd/In2O3–ZrO2for CO2hydrogenation to methanol

“…Compared with the traditional Cu/ ZnO/Al 2 O 3 catalyst, In 2 O 3 catalysts exhibit excellent methanol selectivity in CO 2 hydrogenation to CH 3 OH. [18][19][20] It was found that the reactivity and CH 3 OH selectivity can be improved by doping metal oxides or supporting metal nanoparticles on In 2 O 3 . Martin et al obtained high activity using ZrO 2 loaded In 2 O 3 , with the methanol selectivity being close to 100%.…”