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[Display omitted] Thermal runaway is a hazardous risk, occurring more readily in high-energy–density lithium-ion batteries (LIBs), which leads to a rapid temperature rise and even combustion or explosion when using flammable electrolyte systems. Flame retardants (FRs), such as trimethyl phosphate (TMPa) and triethyl phosphate (TEP), are commonly utilized due to their effective flame suppression, low toxicity, and excellent thermal stability. However, the lack of in-depth understanding of the flame retardancy mechanism and solid electrolyte interphase (SEI) formation process has made the development of functional electrolytes difficult at present. In this study, we clarified the flame retardancy and interfacial reaction mechanisms of low-flammable TMPa localized high-concentration electrolytes (LHCE) using hybrid ab initio and reactive force field (HAIR) schemes. Long-term HAIR simulation reveals that phosphorous radicals produced by the decomposition of TMPa capture carbon radicals, encouraging their polymerization into low-flammable oligomers, while fluorine-containing solvents in the electrolyte capture hydrogen radicals and produce nonflammable hydrofluoric acid (HF). This synergistic flame retardancy mechanism provides essential atomic-level insights for the rational design of high-safety electrolytes in the future. [ABSTRACT FROM AUTHOR]

Cobalt phthalocyanine (CoPc) anchored on heterogeneous scaffold has drawn great attention as promising electrocatalyst for carbon dioxide reduction reaction (CO2RR), but the molecule/substrate interaction is still pending for clarification and optimization to maximize the reaction kinetics. Herein, a CO2RR catalyst is fabricated by affixing CoPc onto the Mg(OH)2 substrate primed with conductive carbon, demonstrating an ultra‐low overpotential of 0.31 ± 0.03 V at 100 mA cm−2 and high faradaic efficiency of >95% at a wide current density range for CO production, as well as a heavy‐duty operation at 100 mA cm−2 for more than 50 h in a membrane electrode assembly. Mechanistic investigations employing in situ Raman and attenuated total reflection surface‐enhanced infrared absorption spectroscopy unravel that Mg(OH)2 plays a pivotal role to enhance the CO2RR kinetics by facilitating the first‐step electron transfer to form anionic *CO2− intermediates. DFT calculations further elucidate that introducing Lewis acid sites help to polarize CO2 molecules absorbed at the metal centers of CoPc and consequently lower the activation barrier. This work signifies the tailoring of catalyst‐support interface at molecular level for enhancing the turnover rate of CO2RR. [ABSTRACT FROM AUTHOR]

The performance of a lithium metal battery (LMB) with liquid electrolytes depends on the realization of a stable solid electrolyte interphase (SEI) on the Li anode surface. According to a recent experiment, a high-concentrated (HC) dual-salt electrolyte is effective in modulating the SEI formation and improving the battery performance. However, the underlying reaction mechanism between this HC dual-salt electrolyte and the lithium metal anode surface remains unknown. To understand the SEI formation mechanism, we first performed 95 ps ab initio Molecular Dynamics (AIMD) simulation and then extend this AIMD simulation to another 1 ns by using Hybrid ab Initio and Reactive Molecular Dynamics (HAIR) to investigate the deep reactions of such dual-salt electrolytes consists of lithium difluorophosphate and lithium bis(trifluoromethanesulfonyl)imide in dimethoxyethane (DME) solvent at lithium metal anode surface. We observed the detailed reductive decomposition processes of DFP− and TFSI−, which include the formation pathway of CF3 fragments, LiF, and LixPOFy, the three main SEI components observed experimentally. Furthermore, after extending the simulation to 1.1 ns via the HAIR scheme, the decomposition reactions of DME solvent molecules were also observed, producing LiOCH3, C2H4, and precursors of organic oligomers. These microscopic insights provide important guidance in designing the advanced dual-salt electrolytes for developing high-performance LMB. [ABSTRACT FROM AUTHOR]

Abstract Chemical looping gasification (CLG) is expected to act as an efficient novel technique realizing energy conversion, but solid fuel CLG suffers from inadequate fixed carbon conversion. Sufficient oxidant would be the grand cure for the torment that ever besets solid fuel CLG. We here reported a strategy to promote cotton fiber CLG to produce syngas with high H 2 /CO ratio by introducing methanol solution for supplying adequate H 2 O and CO. Experiments were performed under various oxygen excess number (Ω) at 850 °C. Ω around 0.3 favors the generation of syngas with high H 2 /CO ratio and high carbon conversion (η). Comparatively experiments concerning effect of methanol solution on cotton fiber CLG verified its significant promotion on syngas generation. Methanol solution can even play a more significant role than water to increase the H 2 /CO ratio and η from 5.64 to 71% to 6.82 and 87%, respectively, while H 2 /CO ratio and η for the direct cotton fiber CLG without water and methanol solution is only 1.28 and 29%. Stoichiometry and thermodynamics analysis further verified the possibility of cotton fiber CLG using methanol solution, which shows a double advantage of waste solution treatment and energy conversion. Highlights • Double advantage of methanol-cotton fiber CLG for waste solution treatment and energy conversion. • High H 2 /CO ratio syngas and carbon conversion. • Reaction stoichiometry and auto-thermal analysis. [ABSTRACT FROM AUTHOR]

Solid electrolyte interphase (SEI) plays a significant role in enhancing the stability and durability of lithium metal batteries (LMBs) by separating highly reactive lithium metal anode (LMA) from the electrolyte to avoid continuous degradation. However, the underlying reaction mechanism is still far from clear. Herein, a hybrid ab initio and reactive force field (HAIR) method is employed to extend the ab initio molecular dynamics (AIMD) to 1 ns, which provides crystal information about the reaction mechanism of elementary reactions that can explain the components and morphology evolution of SEI formation. Specifically, HAIR simulation confirms the two‐electron (2e–) reduction of ethylene carbonate (EC) by releasing CO and CO2, agreeing with phenomenal experiment observation. As the unsaturated intermediates accumulate, polymerization reactions occur, producing linear polyethylene oxide (PEO), Li2OCO2CH2CH2, Li2OCO2(CH2)4, etc., which regulate the formation of outer organic layer (OOL) that consists of linear polyethylene oxide (PEO), Li2OCO2CH2CH2, Li2OCO2(CH2)4, etc., and the inner inorganic layer (IIL) mainly consists of LiF and Li2O. Simulations at low concentration (LC, 1M) and high concentration (HC, 5M) reveal significantly different reaction pathways when HC electrolyte can significantly promote the formation of homogenous LiF that has been regarded as an important component to facilitate robust SEI. [ABSTRACT FROM AUTHOR]

We show that a Single-Atom Electrocatalyst (SAC) for the Nitrogen Reduction Reaction (NRR) can provide an environmentally green alternative to the Haber–Bosch high-temperature high-pressure process, replacing the water gas shift production of H2 with H extracted from water. Anchoring the single atom on a two-dimensional substrate provides control to tune NRR catalytic performance toward a SAC possessing high utilization, high activity, and high selectivity. Experimental results suggest that this can significantly improve the activity and selectivity of NRR, but the specific reaction mechanism remains uncertain. This makes it difficult to select new catalytic materials for further optimization. Here we use Density Functional Theory to study the NRR catalytic mechanism on a catalytic model using a MoS2 substrate to support a single atom site. We correct for solvation effects on the electrochemical reactions. We started with Fe@MoS2, for which there are promising experimental reports, and conducted a systematic study of the NRR reaction mechanisms. These results show that N2 adsorption, hydrogenation of N2, desorption of NH3, and Hydrogen Evolution are all critical steps affecting the reaction rates. Based on these steps, we scanned 23 transition metal elements to find improved catalysts. We identified Ir@MoS2 (Mo top site) as the best candidate, predicted to have good catalytic activity and selectivity with 64.11% Faraday Efficiency. These results on the mechanism for NRR and the in silico search for alternative catalysts provide new promising targets for synthesizing novel and efficient SAC@MoS2 NRR catalysts. [ABSTRACT FROM AUTHOR]

Ni-based single-atom catalysis (Ni-SAC) has been experimentally reported with superior performance in reducing CO2 to CO. However, due to the ambiguities in its structures, the active sites of Ni-SAC that are responsible for superior performance have not yet been resolved. This work investigates the CO2 reduction reaction (CO2RR) mechanism on Ni-SAC by carrying out quantum mechanics (QM) simulation to consider both solvation effects. After exploring multiple possible combinations of N, S, and C, we distinguish a Ni-SAC site with two C, one S, and one N, representing the best performance. The predicted formation energy is closely consistent with experimental onset potential. Our prediction also suggests further improvement by finely tuning the electronics state of metal sites by changing the SAC support. [ABSTRACT FROM AUTHOR]