Asymmetric Fe-O₂-Ti structures accelerate reduced-layer-Fe^II "electron" conversion: Facilitating photocatalytic nitrogen fixation

As a green and sustainable method for ammonia production, solar photocatalytic nitrogen fixation (PNRR) provides a new approach to slowing down the consumption of non-renewable energy resources. Given the extremely huge energy required to activate inert nitrogen, a rational design of efficient nitrogen fixation catalytic materials is essential. This study constructs defective Ti3+-Ti(3)C(2)Ox to regulate the NH2-MIL-101(Fe) reduced layer-Fe-II 'electron' transition; meanwhile, the heterojunction interface electronic structure formed by coupling promotes catalytic charges' transfer/separation, while the interface-asymmetric Fe-O-2-Ti structure accelerates the response with nitrogen. It is shown that the heterojunction NM-101(Fe-II/Fe-III)-1.5 exhibits a 75.1 % Fe-II enrichment (Fe-II:Fe-III), which successfully impedes the fouling relationship between the two (Fe-II/Fe-III). Mossbauer spectroscopy analysis demonstrates that the presence of D1-high spin state Fe-III and D2-low/medium spin state FeII structures in the heterojunction boosts the PNRR activity. Furthermore, it is found that the defective state Ti3+-Ti(3)C(2)Ox modulation enhances the reduced nitrogen fixation capacity of the heterojunction (CB = -0.84 eV) and decreases the interfacial charge transfer resistance, yielding 450 umol center dot g(-1)center dot h(-1) ammonia. Furthermore, this study modulates the charge ration of the catalyst reduction layer by constructing a chargeasymmetric structure with Ti3+-deficient carriers; this method provides a potential opportunity for enhancing photocatalytic nitrogen fixation in the future.