Simple Electronic Descriptor for Predicting the Catalytic Activity of Ammonia Synthesis and Decomposition

Abstract

Ammonia (NH3) has emerged as one of the most effective hydrogen carriers for the hydrogen economy owing to its high hydrogen content, its carbon-free nature, and well-established infrastructure. However, the synthesis and decomposition of NH3 are energy-intensive and require high-temperature and high-pressure conditions. To overcome these challenges, the development of efficient catalysts that can operate under milder conditions is crucial. Hence, the design of cost-effective and highly efficient catalysts is required. While nitrogen adsorption energy (Ead(N)) has been reported as a useful descriptor for designing and screening catalytic materials for NH3 synthesis and decomposition, its fundamentals are not well understood, and a more simplified descriptor is still needed for the massive screening of catalyst candidates. Hence, we performed density functional theory (DFT) calculations on 11 metal surfaces to identify alternative descriptors. Our findings show that d-band filling (fd) accurately predicts the experimental catalytic activity of transition-metal-based catalysts for both NH3 synthesis and decomposition.