Bio‐Inspired Leaf‐Mimicking Nanosheet/Nanotube Heterostructure as a Highly Efficient Oxygen Evolution Catalyst

Plant leaves represent a unique 2D/1D heterostructure for enhanced surface reaction and efficient mass transport. Inspired by plant leaves, a 2D/1D CoO(x) heterostructure is developed that is composed of ultrathin CoO(x) nanosheets further assembled into a nanotube structure. This bio‐inspired architecture allows a highly active Co(2+) electronic structure for an efficient oxygen evolution reaction (OER) at the atomic scale, ultrahigh surface area (371 m(2) g(−1)) for interfacial electrochemical reaction at the nanoscale, and enhanced transport of charge and electrolyte over CoO(x) nanotube building blocks at the microscale. Consequently, this CoO(x) nanosheet/nanotube heterostructure demonstrates a record‐high OER performance based on cobalt compounds reported so far, with an onset potential of ≈1.46 V versus reversible hydrogen electrode (RHE), a current density of 51.2 mA cm(−2) at 1.65 V versus RHE, and a Tafel slope of 75 mV dec(−1). Using the CoO(x) nanosheet/nanotube catalyst and a Pt‐mesh, a full water splitting cell with a 1.5‐V battery is also demonstrated.