First-principles study of CO2 activation on pristine and defected XO2 (X= Pd, Pt) monolayers.

Carbon dioxide (CO2) capture is crucial to address both energy and environmental challenges. In this study, density functional theory (DFT) calculations are performed to investigate the adsorption behaviour of the CO2 molecule on pristine (P-XO2) and vacancy-defective (V-XO2) XO2 (X = Pd, Pt) monolayers (MLs). XO2 MLs exhibit a semiconducting natureand to study vacancies, we created X monovacancy (VX-XO2), O monovacancy (VO-XO2), and X-O divacancy (VX/O-XO2). Our findings reveal that CO2 adsorbs physically on PdO2 and PtO2 MLs with adsorption energies (Ead) of -18.67 and -19.83 kJ/mol, respectively, and minimal Bader charge transfer (-0.004 e- in both cases). Creation of Pd and O vacancies in PdO2 ML increases the magnitude of Ead for CO2, while the nature of adsorption remains the same. On the other hand, the CO2 molecule adsorbs chemically on VPd/O-PdO2 ML with an Ead of -55.47 kJ/mol and Bader charge transfer of 0.668e-. Also, the CO2 molecule bends after adsorption, which confirms its activation for further conversion. Similarly, CO2 adsorption on VO-PtO2 and VPt-PtO2 MLs falls in the category of physisorption due to Ead of -23.18 and -21.56 kJ/mol, respectively. Presence of Pt and O divacancy increases Ead to -29.89 kJ/mol. Thus, among all XO2 MLs, VPd/O-PdO2 ML appeared as a promising catalyst for activation and further electrochemical conversion of CO2.