Remote Carbon Monoxide Spillover Improves Tandem Urea Electrosynthesis

Abstract

Electrocatalytic urea synthesis from carbon dioxide (CO₂) and nitrate (NO₃⁻) offers a promising alternative to traditional industrial methods. However, current catalysts face limitations in the supplies of CO* and N_related* intermediates, and their coupling, resulting in unsatisfactory urea production efficiency and energy consumption. To overcome these challenges, we carried out tandem electrosynthesis approach using ruthenium dioxide-supported palladium-gold alloys (Pd₂Au₁/RuO₂). This catalyst system effectively catalyzes CO₂-to-CO* conversion on Pd₂Au₁ and NO₃⁻-to-NH₂* conversion on RuO₂. Crucially, the minimized work function difference between two components promotes remote CO* spillover from Pd₂Au₁ to RuO₂, improving effective coupling of CO* and NH₂* for urea production. Our catalyst demonstrated exceptional performance, achieving a record-high Faradaic efficiency for urea (FE_urea) of 75.6±0.5 % and a urea production rate (r_urea) of 73.5±0.8 mmol g_cat⁻¹ h⁻¹. Notably, this was accomplished with an ultralow energy consumption of 18.9 kWh kg_urea⁻¹. We also successfully demonstrate the long-term stability of our catalyst in a flow cell, achieving over 160 h of uninterrupted urea and formate production with consistent profitability. This achievement represents a significant step towards the large-scale practical application of sustainable urea electrosynthesis.