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 Nrelated* 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 (FEurea) of 75.6±0.5 % and a urea production rate (rurea) of 73.5±0.8 mmol gcat−1 h−1. Notably, this was accomplished with an ultralow energy consumption of 18.9 kWh kgurea−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.