Hydrogenation-Facilitated Spontaneous N-O Cleavage Mechanism for Effectively Boosting Nitrate Reduction Reaction on Fe2B2 MBene

The electrochemical reduction of toxic nitrate wastewater to green fuel ammonia under mild conditions has become a goal that researchers have relentlessly pursued. Existing designed electrocatalysts can effectively promote the nitrate reduction reaction (NO₃RR), but the study of the catalytic mechanism is not extensive enough, resulting in no breakthroughs in performance. In this study, a novel mechanism of hydrogenation-facilitated spontaneous N-O cleavage was explored based on density functional theory calculations. Furthermore, the <i>E</i>_ad-*OH (adsorption energy of the adsorbed *OH) was used as a key descriptor for predicting the occurrence of spontaneous N-O bond cleavage. We found that <i>E</i>_ad-*OH < -0.20 eV results into spontaneous N-O bond cleavage. However, excessively strong adsorption of OH* hinders the formation of water. To address this challenge, we designed the eligible Fe₂B₂ MBene, which shows excellent catalytic activity with an ultra-low limiting potential for NO₃RR of -0.22 V under this novel reaction mechanism. Additionally, electron-deficient Fe active sites could inhibit competing hydrogen evolution reactions (HERs), which provides high selectivity. This work may offer valuable insights for the rational design of advanced electrocatalysts with enhanced performance.