Herein, a self-charging mechanism of rechargeable aluminum (Al) batteries with Chevrel phase molybdenum sulfide (Mo 6 S 8 ) cathode is reported. The results unambiguously reveal that the self-charging is a spontaneous disproportionation of Al intercalated Mo 6 S 8 originated from the dynamic shift of Al between occupied sites during Al intercalating and resting. The theoretical study indicates that the fully Al intercalated Mo 6 S 8 in the format of Al 4/3 Mo 6 S 8 is kinetically accessible driven by electrochemical overpotential but thermodynamically unstable due to the repulsion between Al 3+ cations. This mechanism is a true self-charging with no input of any form of energy, thus distinctly superior to the previously reported self-charging mechanisms. Based on this discovery, a semi-flow Al Mo 6 S 8 battery is designed and demonstrated with long-lasting discharge capability and high capacity.
Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo 6 S 8 /Cu electrode by in-situ reaction between MoS 2 and Cu. The Chevrel phase electrode exhibits strong binding at the electrocatalyst-support interface with weak adhesion at electrocatalyst-bubble interface, in addition to fast hydrogen evolution and charge transfer kinetics. These features facilitate the achievement of large current density of 2500 mA cm −2 at a small overpotential of 334 mV which operate stably at 2500 mA cm −2 for over 100 h. In-situ total internal reflection imaging at micrometer level and mechanical tests disclose the relationships of two interfacial forces and performance of electrocatalysts. This dual interfacial engineering strategy can be extended to construct stable and high-performance electrodes for other gas-involving reactions.
Sundaram Chandrasekaran,Tingting Ma,Zhichang Hu,Qianying Liu,Chao Zhan,Yan Li,Chris Bowen,Huidan Lu,Yongping Liu
Chevrel-phase metal sulfides are known to be promising materials for energy conversion and storage applications. However, a detailed understanding of the intrinsic kinetic mechanisms of electrocatalytic bifunctional hydrogen and oxygen evolution reactions (HER/OER) on NiMo 3 S 4 -based Chevrel-phases is lacking. Herein, novel ultrathin self-assembled nanosheets of NiMo 3 S 4 are coupled with transition metal atoms (M/N-NiMo 3 S 4 ; where M = Co, Fe, and Cu) were formed by a facile hydrothermal approach. Notably, the Co/N-NiMo 3 S 4 electrocatalyst exhibits excellent performance in terms of ultralow overpotentials of 78, 208, 282, and 307 mV at 10, 100, 500, and 1000 mA cm −2 for the HER; and 186, 204, and 225 mV at 50, 100, and 300 mA cm −2 for the OER, respectively. Experimental and first principle calculations demonstrate that Co atoms coupling with edge Ni atoms results in d‐electron delocalization on Co/N-NiMo 3 S 4 , signifying the efficient charge transfer to improve overall water electrolysis. In addition, an upshift in the d‐band center of Co/N-NiMo 3 S 4 can optimize the free energies of a variety of reaction intermediates for water adsorption and dissociation; thereby facilitating the robust alkaline overall water electrolysis at 1.47 V. This work therefore greatly deepens the understanding of the bifunctional hydrogen and oxygen evolution reaction of Chevrel-phase electrocatalysts.
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