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ABSTRACT:The use of a petaloid shape for the bottom design for carbonated PET bottles is widespread. Through this study, the causes of bottom cracking were investigated and a novel petaloid bottom was designed. The variations of the physical properties of PET according to the stretch ratio were examined and the stretch ratios in the blown bottle were analyzed. Cracking phenomena of the bottom were observed by a solvent-cracking test. The effective stress and the maximum principal stress in a carbonated bottle were analyzed by computer simulation. It was concluded that the bottom crack occurs because of not only the insufficient strength of material due to the insufficient stretch of PET but also to the coarse design of the petaloid shape. The highest maximum principal stress occurred at the valley in the petaloid bottom of the bottle and this strongly affected the cracking in the bottom. The petaloid shape was redesigned to minimize the maximum principal stress, and this resulted in increasing the crack resistance.

Hydrazine‐assisted water electrolysis provides new opportunities to enable energy‐saving hydrogen production while solve the issue of hydrazine pollution. Here, we report the synthesis of compressively strained Ni2P as a bifunctional electrocatalyst for boosting both the anodic hydrazine oxidation reaction (HzOR) and cathodic hydrogen evolution reaction (HER). Different from a multistep synthetic method that induces lattice strains by creating core‐shell structures, we develop a facile strategy to tune strains of Ni2P via the dual cation‐codoping. The obtained Ni2P with a compressive strain of −3.62% exhibits significantly enhanced activity for both the HzOR and HER than counterpart with tensile strains and without strains. Consequently, the optimized Ni2P delivers current densities of 10 and 100 mA cm−2 at small cell voltages of 0.16 and 0.39 V for hydrazine‐assisted water electrolysis, respectively. Density functional theory (DFT) calculations reveal that the compression strain promotes water dissociation and concurrently tunes the adsorption strength of hydrogen intermediates, thereby facilitating the HER process on Ni2P. As for the HzOR, the compression strain reduces the energy barrier of potential‐determining step (PDS) for the dehydrogenation of *N2H4 to *N2H3. Clearly, this work not only paves a facile pathway to synthesis lattice‐strained electrocatalysts via the dual cations‐codoping.This article is protected by copyright. All rights reserved

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