Multi-dimensionally hierarchical self-supported Cu@Cu₂₊₁O@Co₃O₄ heterostructure enabling superior lithium-ion storage and electrocatalytic oxygen evolution

Here, we propose a multi-dimensionally hierarchical self-supported Cu@Cu₂₊₁O@Co₃O₄ heterostructure as superior bifunctional material for lithium-ion storage and electrocatalytic oxygen evolution via rapid in-situ oxidation-electrodeposition-annealing treatment. The 3/1/2-dimensional hybridization heterostructure rationally organized by three-dimensional Cu foam, one-dimensional Cu₂₊₁O nanowires and two-dimensional Co₃O₄ nanosheets achieves remarkable synergistic interactions. In brief, the free-standing Cu foam framework enables remarkable structure robustness, electronic conductivity and electrolyte infiltration. Meanwhile, the in-situ grown Cu₂₊₁O nanowires with excess metal defects indeed provide certain activity, effectively adjust the size and distribution of anchored Co₃O₄ nanosheets and dramatically shorten the diffusion pathway of ions and electrons. Moreover, the constructed interfaces between Cu₂₊₁O and Co₃O₄ further yield sufficient electrochemically active surface area. In consequence, Cu@Cu₂₊₁O@Co₃O₄ heterostructure delivers superior lithium-ion storage capacity and electrocatalytic oxygen evolution activity. Specifically, a prominent and stable discharge capacity of 1090 mAh g⁻¹ can be delivered after 200 cycles at 500 mA g⁻¹. Even when the current density is elevated to 5000 mA g⁻¹, remarkable discharge capacity of 601 mAh g⁻¹ still can be yielded. As for the electrocatalytic oxygen evolution activity, Cu@Cu₂₊₁O@Co₃O₄ heterostructure demonstrates a particularly low overpotential of 223 mV at 10 mA cm⁻² and Tafel slope of 46.3 mV dec⁻¹. This strategy may enlighten the researchers on the further development of electrochemically active materials for advanced electrode and catalyst.