Influence of CeO2 Support Morphology on the Structural and NO2-RR Performance of CeO2@Au Catalyst

Abstract

Gold nanoparticles are extensively employed in the field of electrocatalytic nitrite reduction for ammonia synthesis, due to their exceptional conductivity and remarkable stability. However, the properties of a single metal are often limited when compared with compositing different metals, the effect of one plus one is often greater than two. The regulation of the interaction between loaded gold nanoparticles and metal oxide support materials represents an effective strategy for facilitating the reduction of nitrite to ammonia. In this work, we prepared three different structural morphologies of cerium dioxide (CeO2) - cubic (c-CeO2), rod-like (r-CeO2) and granular (p-CeO2), by modulating the hydrothermal temperature. The effect of the morphology of the CeO2 carriers on the surface structure of the composite catalyst, CeO2@Au, was systematically studied and its performance of the electrocatalytic reduction of ammonia from nitrite was explored. It was found that c-CeO2 loaded with Au nanoparticles possessed better electrocatalytic performance with an ammonia yield of 4007.9 μg h-1 mgcat-1 and a Faraday efficiency of 91.2% compared to r-CeO2 and p-CeO2. The results of the characterisation tests conducted using scanning electron microscopy, elemental mapping analysis, inductively coupled plasma, and other techniques, indicated a stronger interaction between c-CeO2 and nano-Au. This led to a greater loading of nano-Au in c-CeO2@Au, which in turn increased the number of active sites. In addition, the results of transmission electron microscopy and X-ray photoelectron spectroscopy tests showed that after the complexation of c-CeO2 with Au, the lattice fringes of c-CeO2 were distorted with defects leading to an increase in the content of oxygen vacancies, which greatly improved the active area of the catalyst. These physicochemical properties endow the c-CeO2@Au catalysts with excellent electrocatalytic nitrite-to-ammonia activity.