Tuning N-Species Adsorption/Desorption Equilibrium by Ni1Aun-SrTiO3 for Artificial Urea Photosynthesis.

Abstract

Inefficient generation of N-related intermediates, stemming from inert adsorption/photoactivation of N₂, has hindered efficient artificial photosynthesis of urea from N₂, CO₂, and H₂O. To overcome this bottleneck, we herein propose a strategy for modulating the adsorption/desorption equilibrium of N-related species using precisely designed bimetallic Ni₁Au_n active sites supported on a strontium titanate (NiAu-STO) semiconductor photocatalyst. This strategy significantly enhances N₂ adsorption/activation and effective generation of N-related intermediates to facilitate C-N coupling for the photocatalytic urea synthesis, affording a considerable urea production rate of 1333.63 µg g_cat. ^-1, with successful crystallization of a collectible solid-phase urea product. Furthermore, we developed a novel reaction-temperature programmed desorption-mass spectrometry tandem monitoring system to elucidate the adsorption behavior of N₂, which can clarify the adsorption behavior of N₂ and confirm the formation of critical N-related intermediates (e.g., *NH₂) on the NiAu-STO photocatalyst. In addition, in situ Raman spectroscopy results further validated the formation of a distinctive C-N coupling intermediate (*NH₂COO^-) on the photocatalyst surface, providing mechanistic insights into urea photosynthesis from N₂, CO₂, and H₂O.