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Promoting the Transformation of Li2S2 to Li2S: Significantly Increasing Utilization of Active Materials for High-Sulfur-Loading Li-S Batteries
No full textLithium-sulfur (Li-S) batteries with high sulfur loading are urgently required in order to take advantage of their high theoretical energy density. Ether-based Li-S batteries involve sophisticated multistep solid-liquid-solid-solid electrochemical reaction mechanisms. Recently, studies on Li-S batteries have widely focused on the initial solid (sulfur)-liquid (soluble polysulfide)-solid (Li2S2) conversion reactions, which contribute to the first 50% of the theoretical capacity of the Li-S batteries. Nonetheless, the sluggish kinetics of the solid-solid conversion from solid-state intermediate product Li2S2 to the final discharge product Li2S (corresponding to the last 50% of the theoretical capacity) leads to the premature end of discharge, resulting in low discharge capacity output and low sulfur utilization. To tackle the aforementioned issue, a catalyst of amorphous cobalt sulfide (CoS3) is proposed to decrease the dissociation energy of Li2S2 and propel the electrochemical transformation of Li2S2 to Li2S. The CoS3 catalyst plays a critical role in improving the sulfur utilization, especially in high-loading sulfur cathodes (3-10 mg cm(-2)). Accordingly, the Li2S/Li2S2 ratio in the discharge products increased to 5.60/1 from 1/1.63 with CoS3 catalyst, resulting in a sulfur utilization increase of 20% (335 mAh g(-1)) compared to the counterpart sulfur electrode without CoS3
An Electronic Nose Based on Copper Oxide Heterojunctions for Rapid Assessment of Liquor
No full textThe novel methods for rapid detection and discrimination of aroma have gained huge attentions not only because of the growing demands for food safety supervision, but also due to their high potentials in monitoring and regulating fermentation process in food production. In this work, a prototype of electronic nose was developed by eight metal oxide semiconductor gas sensors which were fabricated based on two different types of CuO heterojunction, namely ZnO-CuO (n-p) and NiO-CuO (p-p). The sensing performance of as-fabricated electronic nose towards 7 volatile organic compounds (VOCs) gases samples and 4 real samples of Chinese Jing Wine was conducted. The responses were analyzed with standard statistical methods, e.g., hierarchical clustering analysis (HCA), and were distinguished accurately against one another with no errors or misclassifications
Single Ru Sites-Embedded Rutile TiO2 Catalyst for Non-Oxidative Direct Conversion of Methane: A First-Principles Study
No full textNon-oxidative direct methane conversion provides a potentially economic and environmental friendly route for the use of natural gas and shale gas, but this process suffers the disadvantages of low activity and selectivity and harsh operating conditions. Using density functional calculations, we develop the relations in heats of adsorption of CHx(x = 0-4) species and catalytic performance of conventional Fe, Ru, and Co-based catalysts and identify the key factors that affect the activity and selectivity as methane adsorption and the relative strength of CH2 and CH adsorption. Based on the analysis, we design the single Ru sites embedded in rutile TiO2(110) catalyst, which tunes the adsorption strength of CHx compared with the traditional Ru-based catalyst, particularly weakening CH adsorption relative to CH2 adsorption, thus leading to increased activity, improved selectivity toward ethylene, and strong resistance toward coking. This work highlights the impact of surface coordination environment, achieving fundamental insight that can be used to design and develop improved catalysts for direct methane conversion and other important reactions of technological interest
On-Surface Fabrication of Small-Sized Nanoporous Graphene
No full textFrom the interplay of high-resolution scanning tunneling microscopy and density functional theory calculations, we have successfully obtained small-sized nanoporous graphene via a hierarchical reaction pathway involving two different kinds of reactions (Ullmann coupling and cyclodehydrogenation) of hexakis(4-bromopheny)benzene molecules (HEX-6Br) on Au(111)
