Lewis acid-triggered hydroxyl spillover enables selective urea electrooxidation to nitrite with concurrent energy-saving hydrogen production

Nitrite (NO2⁻) is a high-value chemical pivotal to agriculture and pharmaceuticals, yet its conventional via the Ostwald process is energy-intensive and polluting. Electrochemical urea oxidation reaction (UOR) offers a sustainable NO2⁻ synthesis pathway with concurrent energy-saving hydrogen (H2) production, but suffers from non-selective N2/CO2 pathways. Here, we report Cr3+ Lewis acid sites in Ni3S2 that act as hydroxyl (OH⁻) pumps, dynamically spilling OH⁻ to adjacent Ni sites via a Lewis acid-base interaction. This triggers a urea-to-NO2⁻ pathway, achieving a NO2⁻ yield of 120.98 mg h-1 cm-2 (600 mA cm-2). The OH⁻ spillover accelerates C-N cleavage while suppressing N-N coupling, enabling energy-saving H2 production (3.7 kWh m-3 at 500 mA cm-2) and Zn-urea-air batteries (charging potential 288 mV lower than Zn-air). Techno-economic analysis reveals $1,210.5 per ton of urea processed at 400 mA cm-2. This work establishes OH⁻ spillover as a universal design principle for selective electrocatalysis. Electrochemical urea oxidation can coproduce nitrite and H2, but it typically lacks selectivity. Here, the authors address this issue by designing doped Lewis acid sites to trigger a hydroxyl spillover mechanism, resulting in highly selective nitrite production and efficient energy conversion.