Carbon defects enhanced TEMPO redox cycles for high-efficiency urotropine electrosynthesis

Electrocatalysis provides a sustainable alternative route to produce nitrogen-containing molecules. However, poor carbon-nitrogen (C-N) coupling selectivity and limited current density pose challenges to its widespread adoption. Herein, we introduce a carbon-defect enhanced 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) mediated tandem process to tackle both problems. Our hetero-homogeneous system achieved an exceptional Faraday efficiency of ~99% with industrial-level current density of ~0.6 A·cm ⁻² for electrosynthesis of urotropine. In situ near ambient pressure X-ray photoelectron spectroscopy and density functional theory calculations revealed that the boosted activity originated from the oxidation of TEMPOH on the carbon defective sites, which accelerated the redox cycling of the molecular mediator for urotropine formation. Life cycle assessment indicates that the electrosynthesis of urotropine reduces CO ₂ emissions by up to 30.7% compared to conventional industrial processes. This work highlights the unique catalytic effect of carbon defects on the redox cycling of TEMPO, facilitates electrocatalytic C-N coupling at record selectivity and rate, and offers new insights for designing efficient electrochemical mediated oxidation processes and C-N coupling reactions.