Full-spectrum photofixation of N₂ with remarkable NH₃ production rate of 228 μmol/(g·h) was achieved by W atoms doped Ti₃C₂T_x MXene (W/Ti₃C₂T_x-U) catalyst without sacrificial agents at room temperature. The effects of W doping and ultrasonic intercalation of Ti₃C₂T_x MXene were studied. Scanning transmission electron microscope, electron spin resonance spectra, X-ray photoemission spectroscopy, UV-Vis spectrophotometer, temperature programmed adsorption analyzer and density functional theory calculation were used to characterize the obtained catalysts. Results showed that Ti₃C₂T_x MXene harvested ultraviolet-visible and near-infrared light to generate hot electrons. In addition, the doped W atoms played an effective role in adsorbing and activating N₂ molecules by donating electrons to the anti-bonding orbital of N₂ molecules to elongate the bond length of N≡N.