Black Phosphorene with Removable Aluminum Ion Protection for Enhanced Electrochemical Nitrogen Fixation

The exceptional electronic properties and potential applications of black phosphorus (BP) have garnered significant interest in the fields of electrochemical catalysis and energy storage. However, its poor environmental stability severely hampers its practical use. In this study, an innovative strategy is proposed to protect fresh black phosphorene (BP_ene) against oxidation by adsorbing or weakly bonding aluminum ions (Al³⁺) onto its surface, while facilitating their self‐removal under operating conditions. By leveraging Al³⁺‐protected black phosphorene (Al‐BP_ene) as a catalyst for the electrocatalytic reduction of nitrogen to ammonia (NH₃), the effectiveness of this removable Al³⁺‐protected strategy is demonstrated. Quantitative analysis reveals that Al‐BP_ene maintains structural and compositional stability for over 7 days under ambient conditions, while the Al³⁺ can be readily eliminated through self‐desorption or dissolution in the electrolyte. With highly active sites pre‐protected, Al‐BP_ene exhibits a striking NH₃ yield rate of 55.1 µg h⁻¹ mg _cat⁻¹ and a Faradaic efficiency (FE) of 66.5% in alkaline media, as exemplified by the representative application example. Moreover, it is found that the prepared Al‐BP_ene can tolerate a thermal environment, and a higher NH₃ yield rate of 75 µg h⁻¹ mg _cat⁻¹ at 60 °C is recorded. Undoubtedly, these findings pave the way for broader applications of BP_ene.