Fabrication of Flexible Mesoporous Black Nb₂O₅ Nanofiber Films for Visible‐Light‐Driven Photocatalytic CO₂ Reduction into CH₄

Abstract

Achieving high selectivity and conversion efficiency simultaneously is a challenge for visible-light-driven photocatalytic CO 2 reduction into CH 4 . Here, a facile nanofiber synthesis method and a new defect control strategy at room-temperature are reported for the fabrication of flexible mesoporous black Nb 2 O 5 nanofiber catalysts that contain abundant oxygen-vacancies and unsaturated Nb dual-sites, which are efficient towards photocatalytic production of CH 4 . The oxygen-vacancy decreases the bandgap width of Nb 2 O 5 from 3.01-2.25 eV, which broadens the light-absorption range from ultraviolet to visible-light, and the dual sites in the mesopores can easily adsorb CO 2 , so that the intermediate product of CO* can be spontaneously changed into *CHO. The formation of a highly stable NbCHO* intermediate at the dual sites is proposed to be the key feature determining selectivity. The preliminary results show that without using sacrificial agents and photosensitizers, the nanofiber catalyst achieves 64.8% selectivity for CH 4 production with a high evolution rate of 19.5 µmol g −1 h −1 under visible-light. Furthermore, the flexible catalyst film can be directly used in devices, showing appealing and broadly commercial applications.

Improving the Glucose to Fructose Isomerization via Epitaxial‐Grafting of Niobium in UIO‐66 Framework

“…It is also noted that the binding energy of Nb in 5Nb@UIO-66 possessed higher binding energy than several Nb-based catalysts reported in the literature. [55,69,70] It suggests the Nb species successfully incorporated into the Zroxo cluster of the UIO-66 through a chemical interaction which supports the FTIR analysis result. The Zr 3d species of UIO-66 deconvoluted to 3d 5/2 and 3d 3/2 with the binding energies of 183.14 eV and 185.39 eV, indicating the occurrence of the Zroxo cluster in 5Nb@UIO-66 (Figure 3c).…”

“…The high-resolution XPS spectrum of Nb 3d in 5Nb@UIO-66 deconvoluted to 3d 5/2 and 3d 3/2 due to spin-orbit coupling that appeared at a binding energy of 207.68 eV and 210.31 eV, indicating the Nb 5 + species (Figure 3b). [69] Moreover, the XPS spectrum of Nb 2 O 5 was recorded to compare the binding energy of Nb species in both materials (Figure S7). The binding energies of the Nb 3d 5/2 and Nb 3d 3/2 of Nb 2 O 5 appeared at 207.29 eV and 209.98 eV were slightly lower than the binding energy of Nb in 5Nb@UIO-66 (Figure S7).…”

“…Similarly, O 1s XPS profile of Nb 2 O 5 deconvoluted to 2 peaks at 530.57 eV and 532.71 eV, corresponding to the NbÀ O oxygen lattice, and non-lattice oxygen or adsorbed oxygen, respectively (Figure S8). [69] The thermal gravimetric analysis (TGA) curves of UIO-66 and 5Nb@UIO-66 MOF are depicted in Figure S9a to estimate their thermal stability and chemical environment. The TGA of UIO-66 showed a weight loss of ~3 % up to 160 °C) due to physisorbed/occluded ethanol in the micropores.…”

Photocatalytic CO2conversion: from C1 products to multi-carbon oxygenates

“…In a Nb 2 O 5 /g-C 3 N 4 catalyst, the introduction of Nb-sites allowed to increase the adsorption of other intermediates, such as *CHO. 102 In a WO 3 /BiVO 4 catalyst, the Bi-sites was favorable for the absorption of *CH 2 O intermediates. 103 Second, the distance between active sites can tune the C–C coupling reactions.…”

Ultrafast carrier transport in ultrafine porous 2D polymers for the highly selective photocatalytic reduction of CO2to CH4

“…The reduction process tends to produce CO by-products or compete with H 2 production, which means that the process is unfavorable from both kinetic and thermodynamic point of view. 8,9 Consequently, it is currently difficult to achieve the efficient conversion of photocatalytic CO 2 reduction to CH 4 .…”