Single-Atom or Dual-Atom in TiO₂ Nanosheet: Which is the Better Choice for Electrocatalytic Urea Synthesis?

As rising star materials, single-atom and dual-atom catalysts have been widely reported in the electro-catalysis area. To answer the key question: single-atom and dual-atom catalysts, which is better for electrocatalytic urea synthesis? we design two types of catalysts via a vacancy-anchorage strategy: single-atom Pd₁ -TiO₂ and dual-atom Pd₁ Cu₁ -TiO₂ nanosheets. An ultrahigh urea activity of 166.67 mol_urea  mol_Pd ^-1  h¹ with the corresponding 22.54 % Faradaic efficiency at -0.5 V vs. reversible hydrogen electrode (RHE) is achieved over Pd₁ Cu₁ -TiO₂ , which is much higher than that of Pd₁ -TiO₂ . Various characterization including an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and theoretical calculations demonstrate that dual-atom Pd₁ Cu₁ site in Pd₁ Cu₁ -TiO₂ is more favorable for producing urea, which experiences a C-N coupling pathway with a lower energy barrier compared with Pd₁ in Pd₁ -TiO₂ .