Highly Selective CO<sub>2</sub> Conversion to CH<sub>4</sub> by a N-Doped HTiNbO<sub>5</sub>/NH<sub>2</sub>-UiO-66 Photocatalyst without a Sacrificial Electron Donor
Wenyuan Huang, Ziyi Zhang, Jingwen Xu, Haopeng Cui, Kexin Tang, Danielle Crawshaw, Jinxing Wu, Xiaodong Zhang, Liang Tang, Ning Liu
Abstract
High Resolution Image Download MS PowerPoint Slide Photocatalytic reduction of CO 2 to value-added chemicals is a promising technology for reducing atmospheric CO 2, but selectively producing a specific product still remains a great challenge. In this study, a Z-scheme heterojunction, N-doped HTiNbO 5 /NH 2 -UiO-66(Zr) (referred to as NH-NU), is developed to integrate the advantages of semiconductor photocatalysts and porous CO 2 adsorbents for CO 2 -to-CH 4 conversion. The NH-NU Z-scheme heterojunctions are fabricated via a simple one-pot solvothermal method, enabling the formation of a tight and uniform interface between the two phases, thereby facilitating the separation and transfer of the photoinduced charge carriers, as confirmed by TEM, EPR, electrochemical studies, and work functions. As a result, the as-prepared photocatalyst demonstrates a significant increase in selectivity for CH 4 production through CO 2 photoreduction, achieving a 10-fold enhancement compared to that of the pristine MOF, NH 2 -UiO-66. Moreover, there is no obvious decrease in the photocatalytic activity for CH 4 production across four consecutive cycles. In situ FT-IR spectroscopy and DFT calculations reveal that charge-enriched N-doped NH-NU-3 composites stabilize various C 1 intermediates in multistep elementary reactions, leading to superior selectivity in the CO 2 -to-CH 4 conversion process. This work establishes that efficient and selective heterogeneous catalytic processes can be achieved through the stabilization of reaction intermediates by designing suitable Z-scheme heterojunctions.