Direct Synthesis of Amino Acids from Plastic, Air, and Water.

Amino acids as fundamental building blocks exhibit versatile applications spanning from food science to pharmaceutical development. Conventional biological and chemical synthetic approaches suffer from low efficiency and elevated energy demands. While emerging thermocatalysis and photocatalysis strategies offer promising alternatives, their environmental sustainability is substantially constrained by their reliance on Haber-Bosch-derived ammonia as a nitrogen source, which contributes to a significant carbon footprint. Here we developed a hybrid thermochemical-plasma-electrochemical system for sustainable alanine synthesis directly from end-of-life polylactic acid (PLA) plastic using atmospheric nitrogen as a nitrogen source. The synthetic pathway for alanine production initiates with the thermocatalytic oxidative depolymerization of PLA to pyruvic acid (PA) in aqueous medium under mild conditions (140 °C, 1 MPa air), utilizing a Pt/SiO catalyst with high impurity tolerance. Concurrently, a nitrate-enriched solution is generated through plasma-mediated activation of air and water under ambient conditions. Subsequently, the PA and nitrate solutions are mixed and directly introduced to the electrochemical reactor. We employ a strain-engineered CuBi alloy electrocatalyst capable of stably catalyzing alanine production via co-electrolysis of PA and nitrate. This integrated process establishes a sustainable pathway to valorize low-cost feedstocks into high-value commodity chemicals using renewable energy while mitigating plastic pollution.