Elucidating CO₂ Hydrogenation over In₂O₃ Nanoparticles using Operando UV/Vis and Impedance Spectroscopies

Abstract

In 2 O 3 has emerged as a promising catalyst for CO 2 activation, but a fundamental understanding of its mode of operation in CO 2 hydrogenation is still missing, as the application of operando vibrational spectroscopy is challenging due to absorption effects. In this mechanistic study, we systematically address the redox processes related to the reverse water-gas shift reaction (rWGSR) over In 2 O 3 nanoparticles, both at the surface and in the bulk. Based on temperature-dependent operando UV/Vis spectra and a novel operando impedance approach for thermal powder catalysts, we propose oxidation by CO 2 as the rate-determining step for the rWGSR. The results are consistent with redox processes, whereby hydrogen-containing surface species are shown to exhibit a promoting effect. Our findings demonstrate that oxygen/hydrogen dynamics, in addition to surface processes, are important for the activity, which is expected to be of relevance not only for In 2 O 3 but also for other reducible oxide catalysts.

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

“…The surface oxygen vacancy of In 2 O 3 plays an important role in the activation and hydrogenation of CO 2 . The theoretical prediction was then experimentally confirmed by our group and others. ,− The uniqueness of the In 2 O 3 -based catalyst for CO 2 hydrogenation to methanol is its high methanol selectivity. In CO 2 hydrogenation over the In 2 O 3 catalyst, the catalytic cycle starts from the generation of surface oxygen vacancy by hydrogen adsorption followed by CO 2 adsorption and activation on the generated surface oxygen vacancy, hydrogenation of the adsorbed CO 2 to methanol, and finally the recovery of the perfect In 2 O 3 catalyst surface. ,, …”

“…The surface reduction of N–In 2 O 3 results in a decrease in catalytic performance. On the other hand, the adsorbed CO 2 is partially dissociated into O atoms to heal the surface oxygen vacancies, which is a reflection of CO 2 oxidation . In the stabilization, there is a dynamic balance between the reduction of H 2 and CO and the oxidation of CO 2 .…”

“…In spite of its advantages of good activity and high methanol selectivity, In 2 O 3 usually suffers from over-reduction during the reaction, , causing its deactivation at elevated temperatures. Cao et al found that only the surface oxygen vacancy of In 2 O 3 favors methanol synthesis from CO 2 hydrogenation.…”

Insights into photoinduced carrier dynamics and hydrogen evolution reaction of organic PM6/PCBM heterojunctions

“…The results are consistent with previous works, which indicate that hydrogenation can be a practical strategy to enhance the performance of HER, CO 2 RR, and NRR via refining the electronic density of the active sites. 101–105 The results imply that the C666 sites can serve as superior hydrogen evolution sites given one surrounding C665 site has been hydrogenated.…”

Silicalite-1 Layer Secures the Bifunctional Nature of a CO2 Hydrogenation Catalyst

“…The absorption in visible light ( e . g ., 450–700 nm) was due to the formation of surface OVs by partial reduction. , Hess et al , by using operando UV–vis spectroscopy, systematically elucidated the CO 2 hydrogenation process over In 2 O 3 nanoparticles, where the absorption at ∼700 nm was used to examine the oxygen defect change upon exposure to different gas phases or temperatures. However, from Figure g, the entire UV–vis DRS data did not shift upside along with the increase of visible-light absorbance, probably due to the presence of different zeolites.…”