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

Abstract

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.