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

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⁺-Ti₃C₂Ox 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-O₂-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). Mössbauer spectroscopy analysis demonstrates that the presence of D1-high spin state Fe^III and D2-low/medium spin state Fe^II structures in the heterojunction boosts the PNRR activity. Furthermore, it is found that the defective state Ti³⁺-Ti₃C₂Ox modulation enhances the reduced nitrogen fixation capacity of the heterojunction (CB = -0.84 eV) and decreases the interfacial charge transfer resistance, yielding 450 umol·g^-1·h^-1 ammonia. Furthermore, this study modulates the charge ration of the catalyst reduction layer by constructing a charge-asymmetric structure with Ti³⁺-deficient carriers; this method provides a potential opportunity for enhancing photocatalytic nitrogen fixation in the future.