Atomically dispersed cobalt on niobium oxide enables photothermal nitrogen fixation via nitrogen-hydrogen coupling

Developing highly efficient photothermal catalyst for N₂-to-NH₃ conversion remains a great challenge. Here we report atomically dispersed cobalt on niobium oxide (Co-Nb₂O₅) for NH₃ synthesis through a photothermal NH coupling mechanism. This catalyst exhibits 28-fold enhancement in the rate of NH₃ formation (14 mmol.g^-1.h^-1) over pristine Nb₂O₅ (0.46 mmol.g^-1.h^-1). The mechanistic study reveals that under photothermal stimulation, photoexcited Co 3d orbitals donate electrons into the π* antibonding orbitals of adsorbed N₂, weakening the NN bond and enabling stepwise hydrogenation while reducing the apparent activation energy by more than 50%. Complementary DFT calculations and in-situ spectroscopies reveal that Co sites stabilize key intermediates along the associative distal pathway. These findings manifest single-atom coordination chemistry to control molecular activation and multi-electron transformations for solar-driven nitrogen fixation.