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 CoOx heterostructure is developed that is composed of ultrathin CoOx nanosheets further assembled into a nanotube structure. This bio-inspired architecture allows a highly active Co2+ 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 CoOx nanotube building blocks at the micro-scale. Consequently, this CoOx nanosheet/nanotube heterostructure demonstrates a record-high OER performance based on cobalt compounds reported so far, with an onset potential of approximate to 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 CoOx nanosheet/nanotube catalyst and a Pt-mesh, a full water splitting cell with a 1.5-V battery is also demonstrated.