《Nano Lett.》: Selective CO₂ Photoreduction into CH₄ Triggered by Metal-Vacancy Pair Sites

Jiacong Wu,⁺ Juncheng Zhu,⁺ Wenya Fan,⁺ Dongpo He, Qinyuan Hu, Shan Zhu, Wensheng Yan, Jun Hu, Junfa Zhu, Qingxia Chen,^* Xingchen Jiao,^* and Yi Xie^*

Selectively achieving carbon dioxide (CO₂) photoreduction into methane (CH₄) remains significant challenges, which primarily arises from the complexity of the protonation process. Herein, we designed the metal-vacancy pair sites in defective metal-oxide semiconductors, which anchor the reactive intermediates with a bridged linkage for the selective protonation to produce CH₄. As an example, the oxygen-deficient Nb₂O₅ nanosheets are synthesized, in which the niobium-oxygen vacancy pair sites are demonstrated by the X-ray photoelectron spectroscopy and the electron paramagnetic resonance spectra. In situ Fourier transform infrared spectroscopy monitors the *CH₃O intermediate, a key intermediate for CH₄ production, during the CO₂ photoreduction in the oxygen-deficient Nb₂O₅ nanosheets. Importantly, the built metal-vacancy pair sites regulate the *CH₃O formation step as a spontaneous process, making CO₂ reduction to CH₄ the preferred method. Therefore, the oxygen-deficient Nb₂O₅ nanosheets exhibit CH₄ formation rate of 19.14 μmol g⁻¹ h⁻¹, with the electron selectivity up to 94.1%.

Link: https://pubs.acs.org/doi/10.1021/acs.nanolett.3c04012

Figure 1. Schematic illustration for tailoring the reaction step in CO₂ reduction pathways over the catalyst with (a) the single-metal sites and (b) the metal-vacancy pair sites.