Promoting photocatalytic nitrogen reduction for aqueous nitrogenous fertilizer from organic wastewater over p-BiOBr/n-Bi2MoO6 hetero-nanofibers

Abstract

Photocatalytic nitrogen reduction (PNR) is a potential routine for producing aqueous nitrogenous fertilizer via a green chemistry process but is still limited by a relatively poor efficiency. Considering the dynamic coupling of excited electrons and holes, we introduced organic wastewater oxidation process to substitute the sluggish water oxidation for promoting the PNR reaction. We developed p-BiOBr/n-Bi2MoO6 Z-scheme hetero-nanofibers and experimentally studied their interface charge transfer mechanism in detail. Their strong redox ability and high charge separation efficiency enabled efficient PNR with simultaneous organic pollutant degradation. They have exhibited a PNR rate of up to 911.6 µmol g−1 h−1 L−1 in Rhodamine B (RhB) solution, about 2.5 times higher than that in pure water. Meanwhile, their RhB removal rate reached ∼91.2% in the PNR process (i.e., in N2 saturated solution), close to that in the air (∼96.6%) due to the strong oxidation ability of valence band holes. The proper loading ratio of BiOBr on the hetero-nanofibers and their super-long one-dimensional structures were essential for tuning the charge separation and photocatalytic activity. Moreover, the dual-functional system exhibited efficient photocatalytic performance in a natural water matrix and simulated flowing wastewater scene. Based on a comparative plant cultivation study, the system could effectively convert pollutant solutions into aqueous nitrogenous fertilizers that could promote the healthy growth of nitrogenous sensitive plants. The green and sustainable strategy of PNR for aqueous nitrogenous fertilizer from organic wastewater would have broad applications in energy conservation and environmental remediation.