Tuning excited-state electronic structure in tungsten oxide for enhanced nitrogen photooxidation as fertilizer

Nitrate (NO3-) is an important raw ingredient for fertilizer, but its conventional synthesis is restricted by high energy consumption and CO2 emissions. Though there have been some studies on photocatalytic nitrogen oxidation, the production rate of nitrate is undesirable and the excited-state charge-transfer pathway still re-mains unclear. Herein, we fabricated the V-doped W18O49 nanowires (V-W18O49) for direct nitrate synthesis from N2 photooxidation. The NO3- production rate is as high as 39.85 mu mol g-1 h-1 with exceptional catalytic stability and the photosynthetic nitrate fertilizer was employed to promote the growth of crops. Time-resolved spectroscopic results confirmed that the introduction of V doping in V-W18O49 has created new high-efficiency electron-transfer (ET) pathways from the W-O site to the V-dopant under photoirradiation, which leads to an improved pi-backdonation process that facilitates nitrogen activation. This newly formed ET channel facilitated efficient charge separation and ultrafast photogenerated carriers transfer, thus overcame the sluggish ET kinetics.