Activation of CO2 at chromia-nanocluster-modified rutile and anatase TiO2

Carbon dioxide activation by discandium dioxide cations in the gas phase: a combined investigation of infrared photodissociation spectroscopy and DFT calculations

We present a combined computational and experimental study of CO2 activation at the Sc2O2+ metal oxide ion center in the gas phase. Density functional theory calculations on the structures of [Sc2O2(CO2)n]+ (n = 1-4) ion-molecule complexes reveal a typical end-on binding motif as well as bidentate and tridentate carbonate-containing configurations. As the number of attached CO2 molecules increases, activated forms tend to dominate the isomeric populations. Distortion energies are unveiled to account for the conversion barriers from molecularly bound isomers to carbonate structures, and show a monotonically decreasing trend with successive CO2 ligand addition. The infrared photodissociation spectra of target ion-molecule complexes were recorded in the 2100-2500 cm-1 frequency region and interpreted by comparison with simulated IR spectra of low-lying isomers representing distinct configurations, demonstrating a high possibility of carbonate structure formation in current experiments.

Machine Learning-Driven Discovery of Key Descriptors for CO2 Activation over Two-Dimensional Transition Metal Carbides and Nitrides

Fusing high-throughput quantum mechanical screening techniques with modern artificial intelligence strategies is among the most fundamental ─yet revolutionary─ science activities, capable of opening new horizons in catalyst discovery. Here, we apply this strategy to the process of finding appropriate key descriptors for CO₂ activation over two-dimensional transition metal (TM) carbides/nitrides (MXenes). Various machine learning (ML) models are developed to screen over 114 pure and defective MXenes, where the random forest regressor (RFR) ML scheme exhibits the best predictive performance for the CO₂ adsorption energy, with a mean absolute error ± standard deviation of 0.16 ± 0.01 and 0.42 ± 0.06 eV for training and test data sets, respectively. Feature importance analysis revealed d-band center (ε_d), surface metal electronegativity (χ_M), and valence electron number of metal atoms (M_V) as key descriptors for CO₂ activation. These findings furnish a fundamental basis for designing novel MXene-based catalysts through the prediction of potential indicators for CO₂ activation and their posterior usage.

Impacts of the Catalyst Structures on CO2 Activation on Catalyst Surfaces

Utilizing CO2 as a sustainable carbon source to form valuable products requires activating it by active sites on catalyst surfaces. These active sites are usually in or below the nanometer scale. Some metals and metal oxides can catalyze the CO2 transformation reactions. On metal oxide-based catalysts, CO2 transformations are promoted significantly in the presence of surface oxygen vacancies or surface defect sites. Electrons transferable to the neutral CO2 molecule can be enriched on oxygen vacancies, which can also act as CO2 adsorption sites. CO2 activation is also possible without necessarily transferring electrons by tailoring catalytic sites that promote interactions at an appropriate energy level alignment of the catalyst and CO2 molecule. This review discusses CO2 activation on various catalysts, particularly the impacts of various structural factors, such as oxygen vacancies, on CO2 activation.