Scalable synthesis of multi-shelled hollow N-doped carbon nanosheet arrays with confined Co/CoP heterostructures from MOFs for pH-universal hydrogen evolution reaction

Developing low-cost but efficient hydrogen evolution reaction (HER) electrocatalysts over whole pH values is a significant but daunting task for the large-scale application of electrochemical hydrogen production. Herein, we develop, for the first time, a scalable MOF-assisted strategy for the fabrication and microstructural optimization of multi-shelled hollow N-doped carbon nanosheet arrays with confined Co/CoP heterostructures on carbon cloth (Co/CoP@NC/CC) for boosting HER performances. The key to this strategy is the step-by-step epitaxial growth of unprecedented multilayer ZIF-L arrays on carbon cloth, which are subsequently pyrolyzed and controllably phosphorized to achieve the precise control over the shell number and nanoarchitectures of the Co/CoP@NC/CC. Impressively, the HER performances can be significantly enhanced by increasing hollow shell number, and the optimal triple-shelled hollow Co/CoP@NC/CC exhibits low overpotentials of 86, 78 and 145 mV in acidic, alkaline and neutral media to deliver a current density of 10 mA cm−2, respectively, ranking as one of the best Co-based HER electrocatalysts over whole pH values. Further DFT calculations suggest that the Co/CoP heterostructures can effectively boost the cleavage of H-OH to generate protons and optimize the adsorption energy of hydrogen (ΔGH*), which, together with the large electrode/electrolyte interface and accelerated charge/mass transfer of multi-shelled hollow array structure as well as the good conductivity and dispersity, are responsible for the remarkably improved HER performances. This study not only provides a new toolbox for enriching the family of multi-shelled nanoarchitecture materials, but also points out a general and effective route to develop highly efficient self-supported electrode materials for energy-related applications and beyond.