Efficiently enhanced degradation for the organic pollutants over GO/BiOI/NiWO4 with Z-scheme heterojunction and DFT studies

Abstract

In this work, a series GO/BiOI/NiWO4 (n%GBINWO, n=5, 10, 15, 20) were hydrothermally prepared and applied as photocatalysts for the degradation of organic dyes under ambient conditions. The physico-chemical and microstructure of the studied samples were characterized by XRD, SEM, TEM, TG-DTG, XPS, UV-Vis, EIS, and N2-adsorption. Compared with pure NiWO4, the photocatalytic activity of BiOI/NiWO4 and GO/BiOI/NiWO4 were obviously enhanced, and the highest photocatalytic efficiency of 10% GBINWO was observed to be 98.59% (methylene blue, MB) under the optimized conditions (catalyst weight of 30mg, pH of 3, 3h, 30 °C). The excellent catalytic performance of the 10% GBINWO was due to the existence of interfacial heterojunction, which endows the ternary composite with the large visible light capacity and high charge separation efficiency. Importantly, after the hybrid model constructed with NiWO4 (-1 1 1) and BiOI (0 0 2) was optimized via DFT calculations, a newly-formed bond of I-Bi-O-M (Ni and W), which promoted the transportation of the photogenerated electrons through newly-formed bridge was observed. Furthermore, the difference in degradation efficiency of various organic pollutants was related to the steric hindrance as well as the molecular structure. Moreover, •O2− was also confirmed as the key active species for 10% GBINWO catalyzing the degradation process. Besides, the Z-scheme heterojunction between BiOI and NiWO4 was confirmed by TD-DFT calculations.