W/Mo-heteropoly blue-modified defective W18O49 as Z-Scheme heterostructure photocatalysts for efficient N2 fixation

Abstract

Photocatalytic N2 fixation can convert the abundant but inert N2 into NH3 under atmospheric conditions. However, the dissatisfactory yield rate of NH3 greatly hinders its development. The rational design of a highly efficient N2 fixation photocatalyst enables large-scale ammonia production but is challenging due to the thermodynamic obstacles of N2 activation. Herein, the W/Mo-heteropoly blue modified defective W18O49 heterojunction composite catalysts (r-HPW/W18O49 and r-HPMo/W18O49) are prepared for N2 photofixaiton without sacrificial agents and cocatalysts under ambient conditions for the first time. The heteropoly blue nanoparticles are loaded on the surface of W18O49 by electro-reduction and subsequent solvothermal methods. The as-fabricated r-HPW/W18O49 show unusual activity with NH3 formation rates of 184.54 µmol g−1 h−1, about 2.6 times higher than that of initial W18O49. The excellent photocatalysis property is attributed to the synergistic effect between W18O49 and heteropoly blues. The defective W18O49 provides rich active sites for the effective adsorption of N2 molecules and acts as a robust support to inhibit the aggregation of heteropoly blues. The photo-generated electrons in W18O49 quickly transfer to the heteropoly blues, retarding charge pair recombination and enabling the constructed “Z-Scheme” heterostructure to stronger redox capacity. This work offers a new perspective for preparing advanced heteropoly blues-based N2 photofixation nanomaterials.