Theoretical calculations unveil the charge redistribution over abundant interfaces and the enhanced electronic states of Ru/RuS2 heterostructure. The resulting surface electron‐deficient Ru sites display optimized adsorption behavior toward diverse reaction intermediates, thereby reducing the thermodynamic energy barriers. Experimentally, for the first time the laminar Ru/RuS2 heterostructure is rationally engineered by virtue of the synchronous reduction and sulfurization under eutectic salt system. Impressively, it exhibits extremely high catalytic activity for both OER (201 mV @ 10 mA cm−2) and HER (45 mV @ 10 mA cm−2) in acidic media due to favorable kinetics and excellent specific activity, consequently leading to a terrific performance in acidic overall water splitting devices (1.501 V @ 10 mA cm−2). The in‐depth insight into the internal activity origin of interfacial effect could offer precise guidance for the rational establishment of hybrid interfaces.

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Theoretical calculations unveil the charge redistribution over abundant interfaces and the enhanced electronic states of Ru/RuS2 heterostructure. The resulting surface electron‐deficient Ru sites display optimized adsorption behavior toward diverse reaction intermediates, thereby reducing the thermodynamic energy barriers. Experimentally, for the first time the laminar Ru/RuS2 heterostructure is rationally engineered by virtue of the synchronous reduction and sulfurization under eutectic salt system. Impressively, it exhibits extremely high catalytic activity for both OER (201 mV @ 10 mA cm−2) and HER (45 mV @ 10 mA cm−2) in acidic media due to favorable kinetics and excellent specific activity, consequently leading to a terrific performance in acidic overall water splitting devices (1.501 V @ 10 mA cm−2). The in‐depth insight into the internal activity origin of interfacial effect could offer precise guidance for the rational establishment of hybrid interfaces.

Hitherto, Pt-based catalysts still are state of the art for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), but high dosage, low atom-utilization efficiency, and uncontrollable size of Pt species seriously impede their applications. Given this, we propose an effective way by enhancing Pt–transition metal single-atom interaction. Due to the strong interaction between single-atom Mn sites in Mn–N–C and Pt species, the overgrowth of Pt species is effectively limited with an average size smaller than 2.5 nm. Meanwhile, the regulated electronic structure drives electron transfer from Mn to adjacent Pt sites, endowing catalysts with reduced reaction energy barrier and higher intrinsic activity. As expected, the obtained Pt@Mn-SAs/N-C nanocatalyst with ideal Pt size and ultralow Pt loading (1.98 wt %) exhibits extraordinarily high ORR mass activity at 0.9 V in acidic and alkaline media, which is 11.1 and 14.7 times larger than that of commercial Pt/C, respectively. Moreover, at 30 mV, its HER mass activity is even 33.4 and 18.7 times larger than that of Pt/C. Theory calculation results show that favorable charge density rearrangement and resulting electron-enriched Pt sites, with negatively shifted d-band centers, weaken surface adsorption of key intermediates, boosting ORR/HER activity. This work provides enlightenment for integration of multiple active centers in catalysts.

The epitaxial heterostructure can be rationally designed based on the in situ growth of two compatible phases with lattice similarity, in which the modulated electronic states and tuned adsorption behaviors are conducive to the enhancement of electrocatalytic activity. Herein, theoretical simulations first disclose the charge transfer trend and reinforced inherent electron conduction around the epitaxial heterointerface between Ru clusters and Ni3N substrate (cRu‐Ni3N), thus leading to the optimized adsorption behaviors and reduced activation energy barriers. Subsequently, the defect‐rich nanosheets with the epitaxially grown cRu‐Ni3N heterointerface are successfully constructed. Impressively, by virtue of the superiority of intrinsic activity and reaction kinetics, such unique epitaxial heterostructure exhibits remarkable bifunctional catalytic activity toward electrocatalytic OER (226 mV @ 20 mA cm−2) and HER (32 mV @ 10 mA cm−2) in alkaline media. Furthermore, it also shows great application prospect in alkaline freshwater and seawater splitting, as well as solar‐to‐hydrogen integrated system. This work could provide beneficial enlightenment for the establishment of advanced electrocatalysts with epitaxial heterointerfaces.