Single‐Atom or Dual‐Atom in TiO2Nanosheet: 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 molurea molPd-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 .