Amorphizing of Au Nanoparticles by CeO_x -RGO Hybrid Support towards Highly Efficient Electrocatalyst for N₂ Reduction under Ambient Conditions.

Abstract

Ammonia synthesis is one of the most kinetically complex and energetically challenging chemical processes in industry and has used the Harber-Bosch catalyst for over a century, which is processed under both harsh pressure (150-350 atm) and hightemperature (623-823 K), wherein the energy and capital intensive Harber-Bosch process has a huge energy cost accounting for about 1%-3% of human's energy consumption. Therefore, there has been a rough and vigorous exploration to find an environmentally benign alternative process. As the amorphous material is in a metastable state and has many "dangling bonds", it is more active than the crystallized one. In this paper, CeO_x -induced amorphization of Au nanoparticles anchored on reduced graphite oxide (a-Au/CeO_x -RGO) has been achieved by a facile coreduction method under ambient atmosphere. As a proof-of-concept experiment, a-Au/CeO_x -RGO hybrid catalyst containing the low noble metal (Au loading is 1.31 wt%) achieves a high Faradaic efficiency (10.10%) and ammonia yield (8.3 μg h^-1 mg^-1_cat_. ) at -0.2 V versus RHE, which is significantly higher than that of the crystalline counterpart (c-Au/RGO), and even comparable to the yields and efficiencies under harsh temperatures and/or pressures.