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