Efficiently enhanced N2 photofixation performance of sea-urchin-like W18O49 microspheres with Mn-doping

The urgency of mitigating climate change has prompted us to seek more sustainable approach to ammonia (NH3) synthesis via dinitrogen (N2) photofixation process by using clean solar energy. Herein, a series of Mn-doped sea-urchin-like monoclinic W18O49 microspheres (Mn-W18O49), which are constructed by nanorods with [010] growth orientation, are fabricated using a facile solvothermal process. It is found that the Mn2+ ions can replace the W sites in the W18O49 lattice and intervene the formation of microsphere-like structure, but facilitate the photoinduced charge separation and migration in Mn-W18O49, and thus cause a promoted N2 photofixation ability compared with the single W18O49. Moreover, the surface Mn2+ sites in the monoclinic nanorods of W18O49 microspheres paly multiple roles in promoting the chemisorption of N2 and H2O molecules and weakening the ultra-stable NN bond for the NH3 production through proton coupling process. Among those Mn-W18O49 products fabricated, 3.0% Mn-doped W18O49 product achieves the highest NH3 production activity of 97.9 μmol g−1 h−1 under Xe-lamp’s full spectrum irradiation, 2.3 times higher than that of the single W18O49. The present sea-urchin-like Mn-W18O49 exhibits both excellent durability and efficient N2 photofixation ability, which are of significance in sunlight utilization for artificial N2 fixation and renewable energy conversion.