Insight into rare-earth-incorporated catalysts: The chance for a more efficient ammonia synthesis

Recent studies have suggested that rare earth (RE) elements in catalysts significantly influence the performance of the ammonia synthesis. The REs appear in various forms in the ammonia synthesis catalysts including supports (oxides, hydrides, and nitrides), promotors, and intermetallic. Besides the conventional RE oxide-supporting catalysts (mainly Ru/REO), some new RE-containing catalyst systems, such as electrode and nitride systems, could drive the ammonia synthesis via a benign Mars–van Krevelen mechanism or multi-active-site mode, affording high ammonia synthesis performance under mild conditions. These works demonstrate the great potential of RE-containing catalysts for more efficient ammonia synthesis. This review summarizes the contributions of different kinds of RE-based catalysts and highlights the function mechanism of incorporated REs. Finally, an overview of this area and the challenges for further investigation are provided.