Exploration of iron borides as electrochemical catalysts for the nitrogen reduction reaction

Abstract

In recent years, boron (B) has been identified as a p-block catalyst for the nitrogen reduction reaction (NRR), but N₂ adsorption on the B-site is often weak. In this report, iron has been introduced to improve N₂ fixation. Four iron borides, including FeB, FeB₂, FeB₆(α), and FeB₆(β), have been explored as potential NRR catalysts under the framework of density functional theory (DFT). The key hypothesis is that both Fe and B as active sites may have a synergetic effect on N₂ fixation and reduction. As demonstrated by our calculations, FeB₆(β) offers the best performance in terms of lowest maximum energy required for elementary steps (0.68 eV), which is close to that of recently reported single-atom catalysts. Following this computational work, lightly oxidized iron has been identified as the active site for the electrochemical synthesis of ammonia at room temperature.