Magnetically Propelled Microrobots toward Photosynthesis of Green Ammonia from Nitrates

Abstract Ammonia (NH₃) production is a critical industrial process, as ammonia is a key component in fertilizers, essential for global agriculture and food production. However, the current method of synthesizing ammonia, the Haber‐Bosch process, is highly energy‐intensive, and relies on fossil fuels, contributing substantially to greenhouse gas emissions. Moreover, the centralized nature of the Haber‐Bosch process limits its accessibility in remote or resource‐limited areas. Photochemical synthesis of ammonia, provides an alternate lower energy, carbon‐free pathway compared to the prevailing industrial methods. The photoconversion of nitrate anions, often present in wastewater, offers a greener, more sustainable, and energy‐efficient route for both ammonia‐generation and wastewater treatment. Photochemical and chemical synthesis of ammonia requires intensive mass‐transfer processes, which limits the efficiency of the method. To change the game, in this work, a key new technology of ammonia‐generation, a catalytic ammonia generation (AmmoGen) microrobot, which converts nitrate to ammonia using renewable light energy is reported. The magnetic propulsion of the AmmoGen microrobots significantly enhances mass‐transfer, and expedites the photosynthesis of ammonia. Overall, this “proof‐of‐concept” study demonstrates that microrobots can aid in catalytic small molecule activation and generation of value‐added products; and are envisaged to pave the way toward new sustainable technologies for catalysis.