Highly efficient photocatalytic nitrogen fixation on bio-inspired triphase interface with improved diffusion of nitrogen

Low solubility and slow diffusion of nitrogen (N2) in water are significant impediments for enhancing the efficiency of fixation nitrogen into ammonia (NH3). Herein, we have prepared bio-inspired hierarchical assembly of carbonized loofah sponge@BiOBr-OV/Au (CL@BiOBr-OV/Au) to improve diffusion of nitrogen by immobilization of hydrophilic BiOBr-OV/Au onto hydrophobic CL sponge. The hydrophobic CL sponge provides an optimized directional channel for N2 diffuse to the triphase interface N2 (gas)-H2O (liquid)-BiOBr-OV/Au (solid), which supplies generous N2 for the photocatalytic reaction and replaces the slow diffusion of N2 through the liquid phase. Continuous delivery of N2 can effectively capture generated electrons, thereby preventing the recombination of generated electron-hole and promoting N2 activation. The modification of AuNPs can broaden the photoresponse range of BiOBr-OV, increase oxygen vacancies concentration and enhance N2 adsorption and activation. CL@BiOBr-OV/Au shows an impressive in nitrogen fixation performance with high selectivity and recyclability of 2.64 mmol·gcat−1·h−1, that is 10.2 and 8.0 times compared to CL@BiOBr-OV and BiOBr-OV/Au, respectively. Our work affords a convenient method for the construction of bio-inspired triphase catalysts with a directional N2 transport channel to enhance the efficiency of nitrogen fixation, which also holds great promise for the application in other reactions involving gas consumption.