Photoelectrocatalytic urea synthesis: Surface engineering of the constructions, mechanism insights, and technological challenges.

Traditional urea production methods, primarily the Haber-Bosch and Bosch-Meiser processes, consume substantial amounts of energy and have significant environmental impacts, calling for more sustainable alternatives. Alternatively, photoelectrocatalytic (PEC) urea synthesis utilizes sunlight and electrochemistry to facilitate C-N coupling reactions under mild, environmentally friendly conditions. This review focuses on the recent progress in electrocatalytic, photocatalytic, and photoelectrocatalytic urea synthesis, with a focus on methodology, technological constraints and innovations. Key limitations include low Faradaic efficiencies, restricted catalytic selectivity and mechanistic understanding, and suboptimal charge-transfer processes. We discuss the potential of several photo-electroactive constructions, and quantification methodologies, highlighting a need for standardized testing protocols. Economic aspects of the technology are also discussed, with focus on the industrial feasibility of green urea production. Although PEC synthesis offers notable benefits over conventional methods, it still faces challenges, including catalyst durability, high energy consumption, and limited scalability. This review provides strategies to overcome these challenges and advance PEC urea synthesis toward real-world implementation in sustainable fertilizer manufacturing.