d‐p Orbital Hybridization of Ternary Transition Metal Toward High‐Performance Proton Storage

Abstract Electrochemical proton storage offers grid‐scale energy storage system with long lifespan, great safety, and eco‐friendliness. However, preparing proton storage materials with balanced conductivity, activity, and stability remains challenging due to suboptimal structure design. Herein, we report atomic‐level engineering of d ‐ p orbital hybridization strategy to regulate transition metal (V/Fe) d ‐band centers. Vanadium hexacyanoferrate (VHCF)/RuO x quantum dots (RuO x QDs) heterostructure (VHCF–RuO x QDs) was synthesized via in situ co‐precipitation. The d ‐ p hybridization of Ru's 4 d orbital with VHCF's C≡N 2 p orbital (cyano) induces π‐backdonation and creates “electronic highways” for regulating the d ‐electrons of V/Fe, shifting their d ‐band centers to achieve continuous multi‐electron transfer. Moreover, optimizing the d‐ electron structure reduces the V 5+ ratio and thus decreases vanadium dissolution during cycling. The VHCF–RuO x QDs cathode delivers a large capacity of 162 mAh g −1 at 1 A g −1 , excellent rate capability (127 mAh g −1 at 40 A g −1 ), and ultralong stability over 10 000 cycles. When paired with MoO 3 –MXene anode, the asymmetric full device achieves a high energy density of 53 Wh kg −1 at 1.3 kW kg −1 . The atomic‐level orbital hybridization regulation of d‐ electron structure provides a new direction for high‐performance proton storage.