Search

The performance of lithium‐sulfur batteries is compromised by the loss of sulfur as dissolved polysulfides in the electrolyte and consequently the polysulfide redox shutting effect. Accelerating the conversion kinetics of polysulfide intermediates into sulfur or lithium sulfide through electrocatalysis has emerged as a root‐cause solution. Co−N−C composite electrocatalyst is commonly used for this purpose. It is illustrated here that how the effectiveness can be improved by modulating the coordination chemistry of Co−N−C catalytic sites through introducing Ru species (RuCo−NC). The well‐dispersed Ru in the Co−NC carbon matrix altered the total charge distribution over the Co−N−C catalytic sites and led to the formation of electron‐rich Co−N, which is highly active for the polysulfide conversion reactions. Using Ru to modulate the electronic structure in the Co−N−C configuration and the additional catalytic sites over the Ru−Nx species can manifest optimal adsorption behavior of polysulfides. Consequently, the sulfur cathode with RuCo−NC can reduce the capacity fade rate from 0.11 % per cycle without catalyst (initial capacity of 701 mAh g−1) to 0.054 % per cycle (initial capacity of 1074 mAh g−1) over 400 cycles at 0.2 C rate. The results of this study provide the evidence for a feasible catalyst modification strategy for the polysulfide electrocatalysis. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Urea pretreatment of straw damages fiber structure, while nitrate supplementation of ruminal diets inhibits enteric methane production. The study examined the combined effects of these treatments on ruminal substrate biodegradation and methane production using an in vitro incubation system. Rice and wheat straws were pretreated with urea (40 g kg−1 straw dry matter, DM) and urea + ammonium nitrate (34 + 6 g kg−1 dry matter (DM), respectively), and each straw (control, urea, urea+nitrate) was used in batch culture incubations in three replications (runs). RESULTS: Urea pretreatment increased (P < 0.05) neutral‐detergent solubles (NDS) content (+17%) and in vitro DM degradation of rice straw, in comparison with control. Urea+nitrate pretreatment of rice and wheat straws had higher (P < 0.05) NDS content, in vitro DM degradation and propionate molar proportion, and lower (P < 0.05) acetate:propionate ratio and lower methane production with a decline of methanogens, in comparison to control. CONCLUSIONS: Urea+nitrate pretreatment combines positive effects of urea pretreatment and nitrate supplementation, and can be a potential strategy to improve ruminal biodegradation, facilitate propionate production and reduce methane production from lignified straws. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The performance of lithium-sulfur batteries is compromised by the loss of sulfur as dissolved polysulfides in the electrolyte and consequently the polysulfide redox shutting effect. Accelerating the conversion kinetics of polysulfide intermediates into sulfur or lithium sulfide through electrocatalysis has emerged as a root-cause solution. Co-N-C composite electrocatalyst is commonly used for this purpose. It is illustrated here that how the effectiveness can be improved by modulating the coordination chemistry of Co-N-C catalytic sites through introducing Ru species (RuCo-NC). The well-dispersed Ru in the Co-NC carbon matrix altered the total charge distribution over the Co-N-C catalytic sites and led to the formation of electron-rich Co-N, which is highly active for the polysulfide conversion reactions. Using Ru to modulate the electronic structure in the Co-N-C configuration and the additional catalytic sites over the Ru-N x species can manifest optimal adsorption behavior of polysulfides. Consequently, the sulfur cathode with RuCo-NC can reduce the capacity fade rate from 0.11 % per cycle without catalyst (initial capacity of 701 mAh g -1 ) to 0.054 % per cycle (initial capacity of 1074 mAh g -1 ) over 400 cycles at 0.2 C rate. The results of this study provide the evidence for a feasible catalyst modification strategy for the polysulfide electrocatalysis., (© 2024 Wiley-VCH GmbH.)