Wenhua Zhang

Investigation of the Hydrolysis of Perovskite Organometallic Halide CH3NH3PbI3 in Humidity Environment.

Instability of emerging perovskite organometallic halide in humidity environment is the biggest obstacle for its potential applications in solar energy harvest and electroluminescent display. Understanding the detailed decay mechanism of these materials in moisture is a critical step towards the final appropriate solutions. As a model study presented in this work, in situ synchrotron radiation x-ray diffraction was combined with microscopy and gravimetric analysis to study the degradation process of CH3NH3PbI3 in moisture, and the results reveal that: 1) intermediate monohydrated CH3NH3PbI3·H2O is detected in the degradation process of CH3NH3PbI3 and the final decomposition products are PbI2 and aqueous CH3NH3I; 2) the aqueous CH3NH3I could hardly further decompose into volatile CH3NH2, HI or I2; 3) the moisture disintegrate CH3NH3PbI3 and then alter the distribution of the decomposition products, which leads to an incompletely-reversible reaction of CH3NH3PbI3 hydrolysis and degrades the photoelectric properties. These findings further elucidate the picture of hydrolysis process of perovskite organometallic halide in humidity environment.

Modification of UHMWPE porous fibers by acrylic acid and its adsorption kinetics for Cu2+ removal

Polyacrylic acid-grafted ultrahigh molecular weight polyethylene (UHMWPE-g-PAA) fibers were prepared by radiation-induced grafting of acrylic acid onto UHMWPE porous fibers and were examined for Cu2+ removal from aqueous solutions. The developed fibers were characterized using Fourier transform infrared spectroscopy, mechanics test, scanning electron microscopy and energetic dispersive spectroscopy analysis. It was demonstrated that the UHMWPE fibers were modified successfully with grafted acrylic acid, which conferred excellent hydrophilic performance to UHMWPE porous fibers. The mechanics test indicated that considerable mechanical strength (~0.4xa0GPa) still reserved for the UHMWPE-g-PAA fibers in spite of somewhat radiation degradation. The high-strength, hydrophilic and porous natures render UHMWPE-g-PAA fibers promising as economical adsorbent in wastewater treatment. Prepared under different radiation dose and different degree of grafting of polyacrylic acid (PAA), the adsorption kinetics of the UHMWPE-g-PAA fibers was investigated using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The results reveal a large adsorption capacity of 63xa0mgxa0g−1 for the UHMWPE-g-PAA fibers and the adsorption behavior follows perfectly a pseudo-second-order kinetics model regarding the Cu2+ solution adsorption.