Oxygen vacancy and nitrogen doping collaboratively boost performance and stability of TiO2-supported Pd catalysts for CO2 photoreduction: a DFT study

Abstract

The regulation of interfacial charge transfer, optimization of active sites, and maintenance of stability are effective strategies for improving catalytic performance. The effect of the oxygen vacancy (V_O) and nitrogen doping on these parameters for CO₂ photoreduction on Pd₁₀/TiO₂(101) was studied using density functional theory calculations. The results demonstrate that introduction of the V_O could trigger reversed electron transfer, making the V_O and Pd atoms the active center for CO₂ reduction. However, the V_O is repaired by the dissociated O atom. The combined effect of the V_O and N is related to the position of N. Although the substitutional N (N_S) can delocalize electrons at the V_O, it cannot improve the activity and stability. The interstitial N (N_i) located below the V_O forms N_i–Ti bonds with two Ti atoms adjacent to the V_O. This can delocalize the electrons near the V_O, and the five-fold-coordinated titanium (Ti_5C) replaces the V_O as the active center, thus enhancing the reactivity and protecting the V_O. Further research indicates that the co-modification of the V_O and N_i improves photoexcited electron transfer and distribution, which would in turn promote CO₂ reduction. The results of this study propose that surface defect engineering holds great promise for boosting CO₂ photoreduction by integrating functions of electron density modulation and catalysis.