CuPt Alloy Enabling the Tandem Catalysis for Reduction of HCOOH and NO3− to Urea at High Current Density

Abstract

The formation of urea by electrocatalytic reduction of C₁-reactants and NO₃⁻ is an attractive way to store renewable electricity, close the carbon cycle, and eliminate nitrate contaminants from wastewater. Involving insufficient supply of C₁ reactants and multiple electron transfers makes the reaction difficult to achieve high Faraday efficiency and high yield at high current density. Here, a urea synthesis approach is presented via electrocatalytic reductive coupling between liquid HCOOH and NO₃⁻ on copper foam (CF) loaded Cu₄Pt catalyst with optimized ratios. A urea yield of 40.08 mg h⁻¹ cm⁻² is achieved with FE up to 58.1% at a current density of −502.3 mA cm⁻², superior to the productivity of previously reported catalysts. No degradation is observed over 120-h continuous operation at such a high yield rate. The highly efficient activity of Cu₄Pt/CF can be attributed to the synergetic effect between Pt and Cu sites via tandem catalysis, in which the doped Pt sites enrich liquid HCOOH reactants, promote HCOOH intermolecular dehydration, and form and adsorb large amounts of ^*CO key intermediates. The Cu sites can generate large quantities of the key intermediate ^*NH₂. The Cu₄Pt/CF adsorbed intermediates ^*CO and ^*NH₂ are the basis for subsequent thermodynamic spontaneous C─N coupling.