Developing single-atom electrocatalysts with high activity and superior selectivity at a wide potential window for CO 2 reduction reaction (CO 2 RR) still remains a great challenge. Herein, a porous NiNC catalyst containing atomically dispersed NiN 4 sites and nanostructured zirconium oxide (ZrO 2 @Ni-NC) synthesized via a post-synthetic coordination coupling carbonization strategy is reported. The as-prepared ZrO 2 @Ni-NC exhibits an initial potential of −0.3 V, maximum CO Faradaic efficiency (F.E.) of 98.6% ± 1.3, and a low Tafel slope of 71.7 mV dec −1 in electrochemical CO 2 RR. In particular, a wide potential window from −0.7 to −1.4 V with CO F.E. of above 90% on ZrO 2 @Ni-NC far exceeds those of recently developed state-of-the-art CO 2 RR electrocatalysts based on NiN moieties anchored carbon. In a flow cell, ZrO 2 @Ni-NC delivers a current density of 200 mA cm −2 with a superior CO selectivity of 96.8% at −1.58 V in a practical scale. A series of designed experiments and structural analyses identify that the isolated NiN 4 species act as real active sites to drive the CO 2 RR reaction and that the nanostructured ZrO 2 largely accelerates the protonation process of *CO 2 − to *COOH intermediate, thus significantly reducing the energy barrier of this rate-determining step and boosting whole catalytic performance.

Diffusion and occupancy of magnetic atoms in van der Waals (VDW) layered materials have significant impact on applications such as energy storage, thermoelectrics, catalysis, and topological phenomena. However, due to the weak VDW bonding, most research focus on in‐plane diffusion within the VDW gap, while out‐of‐plane diffusion has rarely been reported. Here, to investigate out‐of‐plane diffusion in VDW‐layered Bi2Te3‐based alloys, a Ni/Bi0.5Sb1.5Te3 heterointerface is synthesized by depositing magnetic Ni metal on a mechanically exfoliated Bi0.5Sb1.5Te3 (0001) substrate. Diffusion of Ni atoms across the Bi0.5Sb1.5Te3 quintuple layers is directly observed at elevated temperatures using spherical‐aberration‐corrected scanning transmission electron microscopy (STEM). Density functional theory calculations demonstrate that the diffusion energy barrier of Ni atoms is only 0.31–0.45 eV when they diffuse through Te3(Bi, Sb)3 octahedron chains. Atomic‐resolution in situ STEM reveals that the distortion of the Te3(Bi, Sb)3 octahedron, induced by the Ni occupancy, drives the formation of coherent NiM (M = Bi, Sb, Te) at the heterointerfaces. This work can lead to new strategies to design novel thermoelectric and topological materials by introducing magnetic dopants to VDW‐layered materials.

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Weak interlayer van der Waals (vdW) bonding has significant impact on the surface/interface structure, electronic properties, and transport properties of vdW layered materials. Unraveling the complex atomistic dynamics and structural evolution at vdW surfaces is therefore critical for the design and synthesis of the next-generation vdW layered materials. Here, we show that Ge/Bi cation diffusion along the vdW gap in layered GeBi2Te4 (GBT) can be directly observed using in situ heating scanning transmission electron microscopy (STEM). The cation concentration variation during diffusion was correlated with the local Te6 octahedron distortion based on a quantitative analysis of the atomic column intensity and position in time-elapsed STEM images. The in-plane cation diffusion leads to out-of-plane surface etching through complex structural evolutions involving the formation and propagation of a non-centrosymmetric GeTe2 triple layer surface reconstruction on fresh vdW surfaces, and GBT subsurface reconstruction from a septuple layer to a quintuple layer. Our results provide atomistic insight into the cation diffusion and surface reconstruction in vdW layered materials.

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