Hierarchical Hollow Nanocages Derived from Polymer/Cobalt Complexes for Electrochemical Overall Water Splitting

Because of the energy crisis and environmental problems, the preparation of highly active, stable, and low-cost electrocatalysts for hydrogen evolution (HER) and oxygen evolution (OER) has great meaning to the sustainable development. In this work, we design a novel hierarchical hollow nanocomposite that is made up of CoP hollow nanoparticles (NPs) and hollow N-doped carbon nanocages (CoP@NCHNCs) derived from polydopamine (PDA)/cobalt nanocontainers (PDA/Co HNCs) through a pyrolysis–phosphidation method. PDA was chosen as the carbon precursor and offered both the oxygen atom for the phosphidation process and pyrrolic N to facilitate the electrocatalyst activity. Benefiting from the unique hierarchical hollow structure and pyrrolic N derived from PDA, the CoP@NCHNCs exhibit outstanding performance for overall water splitting. For OER and HER, only a low overpotential of 304 and 93 mV at 10 mA·cm –2 is needed, respectively. Furthermore, CoP@NCHNCs can be used as anodes and cathodes to achieve 10 mA·cm –2 at 1.62 V. This work demonstrates the potential of hierarchical hollow materials for electrocatalytic overall water splitting and opens a new way to construct highly active electrocatalysts by using polymers as a precursor.