LaRuSi Electride Disrupts the Scaling Relations for Ammonia Synthesis

Electrides have shown their significant advantages in NH₃ synthesis as catalysts or supports under mild conditions. A better understanding of the unconventional reaction kinetics of electrides can greatly promote the development of this kind of novel catalyst. However, most electride-based catalysts are supported ones whose complexity hampers the mechanism study. In this article, the essence behind the catalytic performance of a LaRuSi electride was uncovered using a combination of experiments and first-principles calculations. The LaRuSi electride was found to be capable of disrupting the scaling relations via two mechanisms, which ensured high catalytic performance for NH₃ synthesis. First, a very low N₂ activation energy on a Ru-terminated surface can be achieved without extremely strong adsorption of nitrogen species; then, a second efficient active site (La site) for NH_x formation further significantly reduces the barriers for the overall reaction. A comparative study with CaRuSi, a nonelectride but with the same structure, reveals that the catalytic effect of LaRuSi is indeed derived from the characteristics of anionic electrons. This study delivers insights into the working mechanism of electride-based catalysts and can stimulate the design of new catalytic materials with improved performance.