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

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 (VO) 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 VO could trigger reversed electron transfer, making the VO and Pd atoms the active center for CO2 reduction. However, the VO is repaired by the dissociated O atom. The combined effect of the VO and N is related to the position of N. Although the substitutional N (NS) can delocalize electrons at the VO, it cannot improve the activity and stability. The interstitial N (Ni) located below the VO forms Ni-Ti bonds with two Ti atoms adjacent to the VO. This can delocalize the electrons near the VO, and the five-fold-coordinated titanium (Ti5C) replaces the VO as the active center, thus enhancing the reactivity and protecting the VO. Further research indicates that the co-modification of the VO and Ni 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.