Bifunctional PtCu Nanooctahedrons for the Electrochemical Conversion of Nitrite and Sulfion Into Value-Added Products

The electrochemical reduction of nitrite (NO₂⁻) contaminants to ammonia (NH₃) is a sustainable and energy-saving strategy for NH₃ synthesis. However, this multi-electron reduction process requires an efficient electrocatalyst to overcome the kinetic barrier. Herein, the Pt₂Cu₁ nanooctahedrons are synthesized through a liquid-phase chemical reduction process. The synergistic effect of bimetallic Pt and Cu sites in the Pt₂Cu₁ nanooctahedrons is indispensable for accelerated NO₂⁻ hydrogenation, originating from the strong hydrogen-atoms adsorption capacity at Pt site and the strong NO₂⁻ adsorption capacity at Cu site. Specifically, the introduction of Pt sites can accelerate the accumulation of hydrogenated species on the catalyst surface, which promotes the formation of NH₃. In 0.5 m Na₂SO₄ solution, the Pt₂Cu₁ nanooctahedrons can reduce NO₂⁻ to NH₃ at a yield of 4.22 mg h⁻¹mg_cat⁻¹ and a Faraday efficiency of 95.5% at a potential of −0.14 V versus RHE. Meanwhile, the Pt₂Cu₁ nanooctahedrons also exhibit excellent activity for the sulfion oxidation reaction (SEOR). Using Pt₂Cu₁ nanooctahedrons as bifunctional electrocatalyst, a coupled electrolysis system combining the nitrite electrochemical reduction reaction (NO₂⁻ERR) with the SEOR requires only 0.3 V total voltage, enabling energy-saving electrochemical NH₃ production and collective value-added recovery of nitrite and sulfion waste.