A Facile and Surfactant-Free Electrochemical Synthesis of PtIr Nanocubes towards Ammonia Electro-Oxidation

Abstract

Noble metal Pt catalyst has been identified as excellent electrocatalysts for the ammonia oxidation reaction (AOR). However, Pt’s scarcity, expensiveness, and toxicity hinder its large-scale commercial application. Herein, we report a facile and surfactant-free electrochemical synthesis method for the production of PtIr nanocubes. The PtIr nanocubes were in situ synthesized on carbon paper, and no organic additives were used at any stage in the synthesis of the catalyst. The formation of PtIr nanocubes was attributed to the synergy of the electro-adsorption/desorption of O-containing species and the preferential adsorption of hydrogen adatoms on PtIr(100) with a lower surface free energy. The obtained PtIr nanocubes exhibit an outstanding specific activity (SA) value of 1.34 mA cm−2, which is 1.5 and 3.8 times higher than Pt nanocubes (0.90 mA cm−2) and PtIr nanospheres (0.35 mA cm−2), respectively. The enhanced SA of the PtIr nanocubes can be ascribed to the synergic effects of multiple factors, including the (100) sites of the PtIr nanocubes, the dehydrogenation ability of Ir with respect to ammonia molecules, the electronic effects, and the clean surface of the catalyst due to the use of a “green” synthesis method. This work provides an effective strategy for the “green” synthesis of high-efficiency Pt-based metal catalysts with controllable shapes.