Nonmetallic Si Doping Constructs Cu2O/Co-O-Si Tandem Sites for Neutral Nitrate Reduction Electrocatalysis Toward Ammonia Recovery and Energy-Integrated Applications.

The electrocatalytic nitrate reduction reaction (NO3RR) in neutral media is impeded by sluggish water dissociation and the lack of spatial coordination between distinct active phases. Here, we report a nonmetallic Si doping strategy to construct a Si-CoCu@CF catalyst featuring a "Co-O-Si" interfacial bridge. This unique bonding motif not only regulates the in situ evolution of Cu2O but also establishes robust electronic communication between β‑Co(OH)2 and Cu2O, enabling a precisely engineered tandem catalytic cascade. The catalyst achieves a remarkable NH3 yield rate of 26.6 mg h-1 cm-2 and a Faradaic efficiency (FE) of 97.9% at -1.0 V vs. RHE, maintaining stability for 25 h in a neutral electrolyte of 100 mM NO3 - + 0.5 M Na2SO4. Mechanistic studies reveal a clear functional division: Cu2O governs the swift deoxygenation of NO3 - to NO2 -, while the "Co-O-Si" interface accelerates the Volmer step to enrich the surface with *H, promoting the subsequent hydrogenation of NO2 - to NH3 predominantly through a hydroxylamine pathway. The system further enables struvite recovery, energy-saving methanol-coupled electrolysis, and stable Zn-NO3 - battery operation. This work highlights the potential of nonmetallic elemental bridges in tandem electrocatalysis for integrated nitrate remediation and sustainable ammonia synthesis.