The cover art is attributed to an article entitled “Role of Oxygen Functional Groups in Electrochemical Sodium Ion Intercalation into Oxygen-Functionalized Graphitic Carbon Materials” by Prof. Junichi Inamoto et al. Editor’s Choice of this issue is a systematic computational study on oxygen-functionalized graphite materials for sodium-ion battery applications. Graphene-like graphite (GLG) is a potential candidate of negative electrode materials for sodium-ion battery because of its capability of reversible Na⁺ intercalation/de-intercalation, while the same electrode reactions are hindered with conventional graphite materials. In this work, the authors investigated the role of oxygen-based functional groups for Na⁺-intercalation into GLG by density functional theory calculations. The positive shift of the Na⁺ intercalation potential associated with change in electronic state of GLG upon introduction of oxygen groups was found to be responsible for the favorable electrochemical characteristics.

Graphene-like graphite (GLG) is capable of reversible intercalation/deintercalation of sodium ions while the interlayer distance is almost the same as that of graphite, and elucidation of this factor will provide important insights into the design guidelines for anode materials for sodium-ion batteries. We focused on oxygen-containing functional groups in GLG and investigated their effect on the sodium ion intercalation potential using density functional theory calculations. It was found that the intercalation potential of sodium ions increased significantly in models containing lactones and ketones, leading to the formation of the low-stage intercalation compounds at higher potentials compared to sodium metal deposition reaction. In addition, it was suggested that the introduction of these functional groups changed the electronic state of the materials to increase electron acceptability, which contributed to the increase in potential. Furthermore, the negatively charged oxygen atoms interacted electrostatically with sodium ions, which to some extent had a positive effect on increasing the reaction potential. From these results, it was concluded that the oxygen-containing functional groups in GLG play a crucial role in the performance as anode materials of sodium-ion batteries.

Sodium-based dual carbon batteries (Na-DCBs) are promising next-generation secondary batteries with low environmental impact and minimal resource risk, as they can be constructed without lithium ions, transition metal oxides in the cathode, and copper current collectors in the anode. Our previously reported carbon material, named graphene-like graphite (GLG), exhibits a higher reversible capacity than graphite when used as a cathode active material in lithium-based dual carbon batteries. Additionally, it shows comparable performance to hard carbon as an anode material for sodium-ion batteries. Therefore, in this study, we fabricated a Na-DCB using GLG as both electrodes and evaluated its performance in full-cell configuration. Precycling of the anode facilitated the formation of a stable solid electrolyte interphase (SEI), enabling highly reversible charge–discharge cycles in the full-cell configuration. When the upper cutoff voltage was set to 4.5 V, the maximum capacity reached 139 mAh g⁻¹ based on the mass of the cathode active material. This value largely exceeds previously reported capacities of DCB full cells with graphite cathodes. These results clearly demonstrated the feasibility of constructing high-capacity Na-DCBs using GLG as active materials.

In this paper, composite nanostructures are constructed successfully by combining conductive carbon-based materials with MoS₂. The MoS₂/reduced Graphene Oxide (rGO) composite was synthesized by hydrothermal method, and its morphology, elemental composition and microstructure were characterized in detail. Then, the MoS₂/rGO composite material was modified on the glass carbon electrode (GCE) to construct the methyl parathion (MP) electrochemical sensor. The experimental results show that compared with a single MoS₂/GCE modified electrode, the MoS₂/rGO modified electrode exhibits significantly improved electrochemical performance. This boost can be attributed to the rGO’s high electrical conductivity and its good interface combination with MoS₂, which work together to facilitate electron transport and enhance catalytic activity. In the electrochemical detection of MP, the MoS₂/rGO modified electrode shows excellent sensitivity, and its detection limit of MP reaches 11.92 ng/mL, providing an effective solution for the detection of MP with high sensitivity.