Different shape-controlled synthesis and catalytic property studies on bismuth nanomaterials

Bi with four different morphologies (zero-dimensional (0D) nanoparticles, one-dimensional (1D) nanowires, twodimensional (2D) nanoplates, and three-dimensional (3D) shuttle like structures) was successfully synthesized by changing the synthetic conditions. The Bi nanostructures were characterized in terms of structure, morphology, surface characteristics, optical properties and catalytic activity using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), photoluminescence (PL), UV-vis absorption spectroscopy (UV-Vis) and total organic carbon (TOC) analyzer techniques, respectively. The PL spectra is shown that the reduction of the size of Bi nanomaterials can reduce the recombination rate of photoelectrons and holes, which leads to the effective separation of photocharge carriers and the lowest photoelectron and hole recombination rates. The band gap values of Bi nanoparticles, nanowires, nanoplates and shuttle like structures are 2.71 eV, 2.76 eV, 2.92 eV and 3.22 eV respectively, favouring the harvesting of visible-light. The experimental results of the degradation performance of Bi with different morphologies exhibited that 99.9%, 97.9%, 96.2% and 74.4% degradations of the Rhodamine B (Rh B) was observed for Bi nanoparticles, nanowires, nanoplates and shuttle like structures, respectively. During the degradation of RhB, with the prolongation of treatment time to 90 min, the highest removal rates of chemical oxygen demand (COD) and TOC was 73.5% and 68.4%, respectively. According to TOC analysis, more than 68% of the carbon in the dyes will produce CO2 products. The removal efficiency is attributed to the production of center dot O2-, center dot OH and h+ and their mineralization to RhB. At the same time, the achieved results also reveal that Bi2O3 and BiOCl was found in Bi surfaces before and after catalytic degradation, which was confirmed by XPS and FTIR technology. In addition, Bi with the same morphology performed different catalytic activities in Rh B solution with different pH values. It was found that the degradation efficiency increased evidently when the pH value decreased. The mechanism of Bi photocatalytic activity was proposed based on the results of product analysis, radical capture and XPS analysis.