Nonequilibrium-Induced Defect-Rich Bifunctional Heterojunctions for Highly Selective Paired Electrosynthesis of Ammonium Formate.

Paired electrosynthesis that couples nitrate electroreduction (NO3RR) with polyethylene terephthalate (PET) upcycling offers a promising route to close nitrogen and carbon cycles, yet its implementation is hindered by the lack of bifunctional catalysts capable of operating efficiently under high-current conditions. Here, we report a defect-engineered LD-VO-CoO/Co3O4@C heterojunction catalyst synthesized via flash Joule heating, a nonequilibrium strategy that kinetically stabilizes abundant oxygen vacancies and pronounced lattice distortion. LD-VO-CoO/Co3O4@C achieves an outstanding ammonia yield rate of 78.94 mg h-1 cm-2 with a Faradaic efficiency (FE) of 97.14%, together with excellent stability over 300 h, surpassing all reported monometallic cobalt-based catalysts, as well as efficient oxidation of ethylene glycol to formate (98% of FE). In an integrated configuration, the bifunctional LD-VO-CoO/Co3O4@C catalyst enables stable ampere-level paired synthesis (2 A cm-2 @1.86 V, 180 h at 1 A cm-2). An in situ downstream extension strategy is proposed for the first time, enabling ammonium formate production via direct mixing of anodic and cathodic products, and demonstrating a scalable, high-current paired electrosynthesis platform. Techno-economic evaluation highlights a striking overall profit margin of this configuration (75.7%), along with a substantial reduction in carbon footprint, thereby reversing the long-term dilemma of negative profits for ammonia electrosynthesis.