Hard carbon anode has shown extraordinary potentials for sodium-ion batteries (SIBs) owing to the cost-effectiveness and advantaged microstructure. Nevertheless, the widespread application of hard carbon is still hindered by the insufficient sodium storage capacity and depressed rate property, which are mainly induced by the undesirable pseudographitic structure. Herein, we develop a molten-salt-mediated strategy to regulate the pseudographitic structure of hard carbon with suitable interlayer spacing and enlarged pseudographitic domain, which is conducive to the intercalation capacity and diffusion kinetics of sodium ions. Impressively, the optimized hard carbon anode delivers a high reversible capacity of 320 mAh·g⁻¹, along with superior rate property (138 mAh·g⁻¹ at 2 A·g⁻¹) and stable cyclability over 1800 cycles. Moreover, the in situ Raman spectroscopic study and full-cell assembly further investigate the sodium storage mechanism and practical implement of obtained hard carbon. This work pioneers a low-cost and effective route to regulate the pseudographitic structure of hard carbon materials for advanced SIBs.

Prussian blue analogs (PBAs) are effective precatalysts for the oxygen evolution reaction (OER); however, the underlying mechanism of their electrochemical activation is still not well elucidated. In this study, we designed and constructed PBA-based precatalysts to determine the electrochemical activation mechanism and achieve high-efficiency OER. The PBAs undergo in situ electrochemical transformation to form the corresponding metal (oxy)hydroxides (M(O)OH) as the true OER catalyst. More importantly, the hexacyanoferrate ligands undergo repetitive interfacial coordination/etching with/from M(O)OH during the activation process. The distinct mechanism could achieve in situ Fe doping and enable defect incorporation. The defect-enriched Fe-NiOOH derived from a well-designed NiHCF/Ni(OH)₂ precatalyst requires a low overpotential of 227 mV to reach a current density of 10 mA cm⁻² and works stably at 130 mA cm⁻² over 100 h. This study provides fundamental insights into the electrochemical activation mechanism for developing advanced precatalysts for OER.