Urea Electrosynthesis from Nitrate and CO2 on Diatomic Alloys

Abstract

Urea electrosynthesis from co-electrolysis of NO₃ ^- and CO₂ (UENC) offers a promising technology for achieving sustainable and efficient urea production. Herein, a diatomic alloy catalyst (CuPd₁Rh₁-DAA), with mutually isolated Pd and Rh atoms alloyed on Cu substrate, is theoretically designed and experimentally confirmed to be a highly active and selective UENC catalyst. Combining theoretical computations and operando spectroscopic characterizations reveals the synergistic effect of Pd₁-Cu and Rh₁-Cu active sites to promote the UENC via a tandem catalysis mechanism, where Pd₁-Cu site triggers the early C-N coupling and promotes *CO₂NO₂-to-*CO₂NH steps, while Rh₁-Cu site facilitates the subsequent protonation step of *CO₂NH₂ to *COOHNH₂ toward the urea formation. Impressively, CuPd₁Rh₁-DAA assembled in a flow cell presents the highest urea Faradaic efficiency of 72.1% and urea yield rate of 53.2 mmol h^-1 g_cat ^-1 at -0.5 V versus RHE, representing nearly the highest performance among all reported UENC catalysts.

Keywords: DFT calculations; diatomic alloys; electrochemical urea production; operando spectroscopic measurements; tandem catalysis.