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.

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

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.