Construction of a Co2(OH)2CO3@CoFe-LDH heterostructure on Ni foam with tunable interfacial properties for electrochemical applications

The rational design of hierarchical Co-Ni-Fe-based inorganic materials is of great significance for functional electrochemical applications. Here, a self-supported Co2(OH)2CO3@CoFe-LDH hierarchical heterostructure was constructed in-situ on a conductive nickel foam substrate via a one-step hydrothermal method. A prominent structural feature is that Co2(OH)2CO3 nanoneedles are uniformly and radially anchored on the surfaces of CoFe-LDH nanosheets, which effectively suppresses nanoneedle aggregation. By systematically tuning the Co2+/Fe3+ molar ratio, the effects of composition on phase selectivity, nucleation behavior, and morphological evolution in the multimetallic system were elucidated. The results reveal that CoFe-LDH nanosheets preferentially form at moderate Co2+/Fe3+ ratios, whereas further increasing the Co2+ content leads to heterogeneous nucleation of excess Co2+ species on the LDH surface and induces the directional growth of Co2(OH)2CO3, thereby giving rise to the hierarchical heterostructure. The resulting self-supported electrode exhibits stable oxygen evolution reaction performance under alkaline conditions. In situ Raman spectroscopy reveals a potential-dependent surface reconstruction, evidenced by the attenuation of precursor-related metal-oxygen vibrations and the formation of (oxy)hydroxide species at the heterointerfaces, highlighting the correlation between multimetallic composition regulation and interfacial structural evolution.