In situ evolution of Sn/Cu₂O heterostructure catalysts for modulating selectivity in electrosynthesis of ammonia and urea

Electrocatalytic nitrate reduction reaction (NO₃⁻RR) and its coupling with CO₂ could provide new sustainable pathways for the synthesis of ammonia and urea, respectively. However, their practical applications are hindered by the lack of catalysts with satisfied Faraday efficiency and yield. Herein, we report self-supported electrochemically reconstituted Sn/Cu₂O bifunctional catalysts for the efficient synthesis of ammonia and urea. In the NO₃⁻RR, Sn/Cu₂O-β catalysts electrodeposited for 800 s provided an excellent ammonia yield of 0.496 mmol·h⁻¹·cm⁻² and Faraday efficiency of 98.5%. Besides, Sn/Cu₂O-α catalysts electrodeposited for 400 s achieved the maximum Faraday efficiency of 13.5% and outstanding urea yield of 32.35 μmol·h⁻¹·cm⁻² in C–N coupling. Comprehensive analyses confirm that bi-selectivity to ammonia and urea synthesis could be achieved by modulating the chemical state of Cu in Sn/Cu₂O catalysts, these results are superior to most reported transition metal-based catalysts in synthesis of urea and/or ammonia. In situ Fourier transform infrared (FTIR) spectroscopy revealed that *CONH₂ intermediates are essential for urea synthesis. This work will provide a feasible strategy for the development of bifunctional electrocatalysts for efficient ammonia and urea synthesis.