Photo(electro)catalytic N₂ fixation with water under ambient conditions offers an ideal pathway for clean, sustainable, and decentralized ammonia production and might serve as a potential alternative to the capital and energy intensive Haber-Bosch process. To date, almost all photocatalysts for nitrogen reduction reaction (NRR) suffer from poor selectivity, low activity due to the difficulty in breaking the strong N₂ triple bond, competition with the more favorable hydrogen evolution reaction (HER), and inefficient utilization of the solar spectrum. Here, a photo(electro)chemical setup is demonstrated using a hybrid plasmonic-semiconductor as an active photocatalyst under visible light. Hybrid hollow Au-Ag₂O nanocages are utilized to convert atmospheric N₂ to NH₃ in a pure water system without using sacrificial reagents. The average NH₃ production rate of 28.2 mg m^-2 h^-1 and the solar-to-ammonia (STA) conversion efficiency of 0.017% are achieved under one sun illumination. The apparent quantum efficiency of 1.2% for NH₃ production is obtained with the monochromatic light source at 685 nm, which is among the highest ever-reported values for the photocatalytic NRR. The isotopic labeling experiments using ¹⁵N₂ confirms that supplied N₂ gas is the only source of NH₃ formation in the system. This work showcases the application of plasmonic photocatalysis in the challenging multi-electron nitrogen fixation.