Concurrent Ammonia Synthesis and Alcohol Oxidation Boosted by Glutathione-Capped Quantum Dots under Visible Light

Abstract

Mother nature accomplishes efficient ammonia synthesis via cascade N₂ oxidation by lightning strikes followed with enzyme-catalyzed nitrogen oxyanion (NO_x ^-, x = 2,3) reduction. The protein environment of enzymatic centers for NO_x ^--to-NH₄ ⁺ process greatly inspires the design of glutathione-capped (GSH) quantum dots (QDs) for ammonia synthesis under visible light (440 nm) in tandem with plasma-enabled N₂ oxidation. Mechanistic studies reveal that GSH induces positive shift of surface charge to strengthen the interaction between NO_x ^- and QDs. Upon visible light irradiation of QDs, the balanced and rapid hole and electron transfer furnish GS·radicals for 2e^-/2H⁺ alcohol oxidation and H·for 8e^-/10H⁺ NO₃ ^--to-NH₄ ⁺ reduction simultaneously. For the first time, mmol-scale ammonia synthesis is realized with apparent quantum yields of 5.45% ± 0.64%, and gram-scale synthesis of value-added acetophenone and NH₄Cl proceeds with 1:4 stoichiometry and stability, demonstrating promising multielectron and multiproton ammonia synthesis efficiency and sustainability with nature-inspired artificial photocatalysts.

Keywords: NOx− reduction; ammonia synthesis; glutathione; photocatalysis; quantum dot.