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

Achieving high selectivity and conversion efficiency simultaneously is a challenge for visible-light-driven photocatalytic CO2 reduction into CH4. Here, a facile nanofiber synthesis method and a new defect control strategy at room-temperature are reported for the fabrication of flexible mesoporous black Nb2O5 nanofiber catalysts that contain abundant oxygen-vacancies and unsaturated Nb dual-sites, which are efficient towards photocatalytic production of CH4. The oxygen-vacancy decreases the bandgap width of Nb2O5 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 CO2, 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 CH4 production with a high evolution rate of 19.5 mu mol g(-1) h(-1) under visible-light. Furthermore, the flexible catalyst film can be directly used in devices, showing appealing and broadly commercial applications.

Automated summary

This study reports a facile nanofiber synthesis method for fabricating flexible mesoporous black Nb2O5 nanofiber catalysts, which exhibit high selectivity and conversion efficiency in visible-light-driven photocatalytic CO2 reduction into CH4. The catalysts contain abundant oxygen-vacancies and unsaturated Nb dual-sites, which enhance light absorption and CO2 adsorption, leading to the spontaneous conversion of CO* into *CHO. These catalysts achieve a selectivity of 64.8% for CH4 production with a high evolution rate under visible-light, without the use of sacrificial agents and photosensitizers. The flexible catalyst films also demonstrate promising applications in devices.