Fe-Based Materials for Photocatalytic Nitrogen Reduction to Ammonia: Unique Advantages, Challenges, and Perspectives

Artificial photocatalytic nitrogen reduction to ammonia (NH3) driven by solar energy provides a feasible NH3 production strategy with environmentally sustainable and low energy consumption. However, activating inert nitrogen molecules (N2) with high bond energy remains a challenge for the photocatalytic nitrogen reduction reaction (PCNRR). As important components of natural nitrogenase, Fe species have received extensive attention in view of their capacity to weaken the strong N≡N triple bond. By modifying their local electron density, Fe species cause the adsorbed N2 to shift from polar to nonpolar, lowering N2 stability. Among many photocatalysts, Fe-based photocatalysts have been widely applied as nitrogen fixation materials. In this paper, the latest research progress on Fe-based photocatalysts for PCNRR is reviewed. The basic principle and reaction pathway of PCNRR are presented initially. The determination methods for product ammonia, as well as their benefits and drawbacks, are listed. Subsequently, the applications of Fe-based materials in PCNRR are systematically reviewed from the single-atom Fe, Fe-based metal organic frameworks, iron oxides, and Fe/other atoms codoping. Then, the unique advantages of different types of Fe-based nitrogen fixation photocatalysts are summarized. The authenticity verification of the PCNRR performance is briefly introduced. Finally, the main challenges encountered in the realm of PCNRR are also explored, along with the future prospects. This review aims to present useful guidance for the design of Fe-based nitrogen fixation photocatalysts with high activity, stability, and selectivity.