Efficient water electrolyzers are constrained by the lack of low-cost and earth-abundant hydrogen evolution reaction (HER) catalysts that can operate at industry-level conditions and be prepared with a facile process. Here we report a self-standing MoC–Mo2C catalytic electrode prepared via a one-step electro-carbiding approach using CO2 as the feedstock. The outstanding HER performances of the MoC–Mo2C electrode with low overpotentials at 500 mA cm−2 in both acidic (256 mV) and alkaline electrolytes (292 mV), long-lasting lifetime of over 2400 h (100 d), and high-temperature performance (70 oC) are due to the self-standing hydrophilic porous surface, intrinsic mechanical strength and self-grown MoC (001)–Mo2C (101) heterojunctions that have a ΔGH* value of −0.13 eV in acidic condition, and the energy barrier of 1.15 eV for water dissociation in alkaline solution. The preparation of a large electrode (3 cm × 11.5 cm) demonstrates the possibility of scaling up this process to prepare various carbide electrodes with rationally designed structures, tunable compositions, and favorable properties.

In this paper, we developed an efficient and environment-friendly approach, the molten-salt-electrolysis (MSE), to recover lithium and cobalt from spent LiCoO 2 -based lithium-ion batteries (LIBs). Unlike the conventional ways that employ strong acid lixiviants and reducing agents, the spent LiCoO 2 was electrochemically reduced to either CoO or Co under controlled potentials at the cathode, releasing Li 2 O into molten salts where the Li 2 O combined with CO 2 generated at the carbon anode to produce Li 2 CO 3 . After electrolysis, CoO/Co and Li 2 CO 3 were leached out from the molten salts in water, and the recovery rates of Li and Co were high up to 85% and 99%, respectively. In addition, the LiCoO 2 was regenerated from the recovered CoO and Li 2 CO 3 , exhibiting excellent electrochemical performances as a cathode in a LIB. Overall, the MSE route employs electrons as the reducing agent and molten salt as a solvent to recycle spent LIBs, which could be a simple, comprehensive, and green process for recycling various cathode materials.

An ammonium chloride roasting approach can convert lithium metal oxides to water-soluble lithium and transition metal chlorides at 300 °C, promising an energy-efficient and environmentally benign way to recover end-of-life lithium-ion batteries. Unlike conventional chlorination processes, the roasting of LiCoO2 using NH4Cl as both reducing and chlorination agents is complex, and thus more efforts such as thermodynamics and the underlying mechanism are required to be understood. This paper aims to study the chlorination process by comprehensive thermodynamic analysis and a variety of control experiments such as operating temperature, gas atmosphere, NH4Cl/LiCoO2 mass ratios, and the way of mixing feedstocks. It is found that the chlorination of LiCoO2 is governed by a solid-to-solid reaction mechanism based on thermodynamics, thermal analysis, and roasting products. Finally, the regenerated LiCoO2 delivers a specific capacity of over 139.8 mAh g–1 at 0.5C with a capacity retention rate of 99% after 100 cycles. Overall, the chlorination process can be engineered by adjusting the temperatures, pressure, and contact area between NH4Cl and LiCoO2 to further reduce the energy consumption and thereby increase the utilization of NH4Cl and chlorination efficiencies.

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Production of silicon film directly by electrodeposition from molten salt would have utility in the manufacturing of photovoltaic and optoelectronic devices owing to the simplicity of the process and the attendant low capital and operating costs. Here, dense and uniform polycrystalline silicon films (thickness up to 60 µm) are electrodeposited on graphite sheet substrates at 650 °C from molten KCl-KF-1 mol% K 2 SiF 6 salt containing 0.020-0.035 wt% tin. The growth of such high-quality tin-doped silicon films is attributable to the mediation effect of tin in the molten salt electrolyte. A four-step mechanism is proposed for the generation of the films: nucleation, island formation, island aggregation, and film formation. The electrodeposited tindoped silicon film exhibits n-type semiconductor behavior. In liquid junction photoelectrochemi cal measurement, this material generates a photocurrent about 38-44% that of a commercial n-type Si wafer.

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