PtRu nanocubes as bifunctional electrocatalysts for ammonia electrolysis

Abstract

Co-regulation of the crystal plane and composition is a powerful strategy to effectively enhance the catalytic properties of nanomaterials. Herein, high-quality Pt_xRu nanocubes (Pt_xRu-NCs) with an adjustable composition and exposed (100) planes are synthesized by a simple hydrothermal method. For the ammonia electrooxidation reaction (AOR), Pt₆Ru-NCs show obviously higher mass activity (192 mA mg_Pt⁻¹) and specific activity (1.02 mA cm⁻²) than other Pt_xRu-NCs, Pt-NCs and commercial Pt nanocrystals. Density functional theory calculations demonstrate that the Pt₆Ru (100) plane is more energetically favourable for the AOR than the Pt (100) plane due to the stronger binding of *NH₂ and *NH. For the hydrogen evolution reaction (HER), the optimized Pt₆Ru-NCs also deliver the smallest overpotential (37.6 mV) at 10 mA cm⁻². The high activity of bifunctional Pt₆Ru-NCs for both AOR and HER can be attributed to the crystal surface effect and Pt-Ru bimetallic interactions. A symmetric ammonia electrolyzer constructed here with Pt₆Ru-NCs as the cathode and anode only requires 0.72 V electrolysis voltage for electrochemical hydrogen production.