Effect of loading rate of nano-silver on degradation of methyl orange by AgNPs@SBPN composite catalyst

Abstract

To determine the influence of loading rate of nano-silver on the degradation of pollutants, AgNPs were immobilized on the surface of small black phosphorus nanosheet (SBPN) with different loadings (2.5 wt%, 5 wt%, 7.5 wt% and 10 wt%) and constructed a series of composite photocatalysts, namely AgNPs@SBPN. The structure, size and morphological properties of AgNPs@SBPN were investigated. The photocatalytic performance of bare BP and AgNPs@SBPN was compared. The results confirmed that the surface plasmon resonance effect of loaded AgNPs increased the absorption of visible light and separation efficiency of charges of AgNPs@SBPN. The photocatalytic degradation performance of AgNPs@SBPN was AgNPs loading rate dependent. Compared with the pure BP, degradation rate of methyl orange (MO) increased by 35.3%–187.7% as the loading increased from 2.5 wt% to 7.5 wt%. The findings indicated that too much (>10 wt%) or little nano silver (<2.5 wt%) was not conducive to the rapid transfer of electrons, resulting in low degradation efficiency. Under the optimal condition of AgNPs loading rate (7.5 wt%), the average particle size of AgNPs was 34 nm. About 72.0% MO was degraded within 120 min by 7.5 wt%-AgNPs@SBPN with the photocurrent density of 15.3 μA cm−2. Through liquid chromatography-mass spectrometry analysis, MO may be mineralized into CO2, H2O and NO3− under the oxidation of ·OH and ·O2−.