Lingxing Zan

NiFe (oxy)hydroxide has been widely used as a benchmark anodic catalyst for oxygen evolution reactions (OERs) in alkaline water electrolysis devices; however, the energy saving actually takes contributions from both the anodic OER and cathodic hydrogen evolution reaction (HER). In this work, we observe the catalytic promotion upon the in situ-derived NiFe (oxy)hydroxide from the NiFe alloy monolithic electrode and also point out that the coupled nickel cathode is contaminated, leading to the loss of HER activity and a reduction in overall efficiency. It is found that Ni²⁺ and Fe³⁺ cations are inevitably detached from the anode into the electrolyte and electrodeposited on the nickel cathode after the three-month industrial simulation. This research presents the significant enhancement of the oxygen evolution catalysis using an in situ aging process and emphasizes that the catalytic application should not only be isolated on the half reaction, but a reasonable coupled electrode match to get rid of the contamination from the electrolyte is also of great significance to sufficiently present the intrinsic catalytic yielding for the real application.

Under the ever-growing demand for electrochemical energy storage devices, developing anode materials with low cost and high performance is crucial. This study established a multiscale design of MoS₂/carbon composites with a hollow nanoflower structure (MoS₂/C NFs) for use in sodium-ion batteries as anode materials. The NF structure consists of several MoS₂ nanosheets embedded with carbon layers, considerably increasing the interlayer distance. Compared with pristine MoS₂ crystals, the carbon matrix and hollow-hierarchical structure of MoS₂/C exhibit higher electronic conductivity and optimized thermodynamic/kinetic potential for the migration of sodium ions. Hence, the synthesized MoS₂/C NFs exhibited an excellent capacity of 1300 mA h g⁻¹ after 50 cycles at a current density of 0.1 A g⁻¹ and 630 mA h g⁻¹ at 2 A g⁻¹ and high-capacity retention at large charge/discharge current density (80% after 600 cycles 2 A g⁻¹). The suggested approach can be adopted to optimize layered materials by embedding layered carbon matrixes. Such optimized materials can be used as electrodes in sodium-ion batteries, among other electrochemical applications.

Metallic conductive 1T phase molybdenum sulfide (MoS₂) has been identified as promising anode for sodium ion (Na⁺) batteries, but its metastable feature makes it difficult to obtain and its restacking during the charge/discharge processing result in part capacity reversibility. Herein, a synergetic effect of atomic‐interface engineering is employed for constructing 2H‐MoS₂ layers assembled on single atomically dispersed Fe−N−C (SA Fe−N−C) anode material that boosts its reversible capacity. The work‐function‐driven‐electron transfer occurs from SA Fe−N−C to 2H‐MoS₂ via the Fe−S bonds, which enhances the adsorption of Na⁺ by 2H‐MoS₂, and lays the foundation for the sodiation process. A phase transfer from 2H to 1T/2H MoS₂ with the ferromagnetic spin‐polarization of SA Fe−N−C occurs during the sodiation/desodiation process, which significantly enhances the Na⁺ storage kinetics, and thus the 1T/2H MoS₂/SA Fe−N−C display a high electronic conductivity and a fast Na⁺ diffusion rate.

Metallic conductive 1T phase molybdenum sulfide (MoS₂) has been identified as promising anode for sodium ion (Na⁺) batteries, but its metastable feature makes it difficult to obtain and its restacking during the charge/discharge processing result in part capacity reversibility. Herein, a synergetic effect of atomic‐interface engineering is employed for constructing 2H‐MoS₂ layers assembled on single atomically dispersed Fe−N−C (SA Fe−N−C) anode material that boosts its reversible capacity. The work‐function‐driven‐electron transfer occurs from SA Fe−N−C to 2H‐MoS₂ via the Fe−S bonds, which enhances the adsorption of Na⁺ by 2H‐MoS₂, and lays the foundation for the sodiation process. A phase transfer from 2H to 1T/2H MoS₂ with the ferromagnetic spin‐polarization of SA Fe−N−C occurs during the sodiation/desodiation process, which significantly enhances the Na⁺ storage kinetics, and thus the 1T/2H MoS₂/SA Fe−N−C display a high electronic conductivity and a fast Na⁺ diffusion rate.

CoNi-LDHs with intensively exposed highly active crystal facets manufacturedviaa solvent-induced strategy exhibit outstanding synergistic catalytic performance towards both the OER and HER.

Developing stable but high active metal-nitrogen-carbon (M-N-C)-based hard carbon anode is a promising way to be the alternatives to graphene and blank hard carbon for sodium-ion batteries (SIBs), requiring the precise tailoring of the electronic structure for optimizing the Na⁺ intercalation behavior, yet is greatly challenging. Herein, Fe-N-C graphitic layer-encapsulating Fe₃C species within hard carbon nanosheets (Fe-N-C/Fe₃C@HCNs) are rationally engineered by pyrolysis of self-assembled polymer. Impressively, the Fe-N-C/Fe₃C@HCNs exhibit outstanding rate capacity (242 mAh·g⁻¹ at 2,000 mA·g⁻¹), which is 2.1 and 4.2 times higher than that of Fe-N-C and N-doped carbon (N-C), respectively, and prolonged cycling stability (176 mAh·g⁻¹ at 2,000 mA·g⁻¹ after 2,000 cycles). Theoretical calculations unveil that the Fe₃C species enhance the electronic transfer from Na to Fe-N-C, resulting in the charge redistribution between the interfaces of Fe₃C and Fe-N-C. Thus, the optimized adsorption behavior towards Na⁺ reduces the thermodynamic energy barriers. The synergistic effect of Fe₃C and Fe-N-C species maintains the structural integrity of electrode materials during the sodiation/desodiation process. The in-depth insight into the advanced Na⁺ storage mechanisms of Fe₃C@Fe-N-C offers precise guidance for the rational establishment of confinement heterostructures in SIBs.

Magnesium based secondary batteries are regarded as a viable alternative to the immensely popular Li‐ion systems. One of the largest challenges is the selection of a Mg anode material since the insertion/extraction processes are kinetically slow because of the large ionic radius and high charge density of Mg²⁺. In an attempt to bridge the gap between insertion measurements in 3D composite electrode materials and that in an idealized pure model system, we studied the insertion and diffusion of Mg in a thin, massive layer of Sb deposited on Au by using PITT, CV, and potential step experiments. Sb has been suggested as an insertion material because magnesium can form intermetallic compound with it. The layered crystal structure of Sb leads should facilitate formation of such an intermetallic phase. Mg insertion from a MACC/tetraglyme electrolyte into Sb starts 300 mV positive of the onset potential of Mg deposition as shown by cyclic voltammetry. The molar ratio of Mg to Sb agrees well with the stoichiometry of Mg₃Sb₂ alloy (Zintl‐phase). The diffusion coefficient of Mg‐insertion into Sb – layers and the charge transfer rate have been estimated by the above techniques. Such diffusion coefficients, albeit still somewhat “apparent”, are much more closely related to the true diffusion coefficient in the metal or alloy. The solid‐state diffusion coefficient of Mg into the Sb layers is in the range of 4–8×10⁻¹⁴ cm² s⁻¹. A very high Tafel slope of 370 mV/dec was found in potential step experiments. Mg insertion was further investigated by XPS measurements. Besides Mg and Sb, Al and Cl signals were also detected, particularly at the outer parts of the layer.