Size effects of Ag nanoparticle for N2 photofixation over Ag/g-C3N4: Built-in electric fields determine photocatalytic performance

Abstract One of the main characteristics of metal Ag on semiconductor photocatalysts is Ag particle size effect, which determines its dispersion and electronic structure. In this work, we have studied Ag particles with mean diameters of 9.3–33.2 nm on N2 photofixation catalyst g-C3N4 by a method of ultra-low temperature reduced-deposit. Characterizations and N2 photofixation results show that the largest photoelectron life- time (τ = 0.29 ms) is obtained over the middle-sized Ag particles. Taking the activity of N2 photofixation as an example, the NH3 production rate shows a volcanic trend with the decrease of Ag particles size. The highest activity was gained over Ag4%/C3N4 (−40) catalyst prepared at the temperature of −40 °C (particle size 13.2 nm). So, the N2 photofixation rate has a volcano-shape relationship with Ag NPs (nano-particle) size indicated in this work.