Strategic Atomic Layer Deposition and Electrospinning of Cobalt Sulfide/Nitride Composite as Efficient Bifunctional Electrocatalysts for Overall Water Splitting.

Abstract

Reported herein is comprehensive study of a highly active and stable cobalt catalyst for overall water splitting. This composite SFCNF/Co1- x S@CoN, consisting of S-doped flexible carbon nanofiber (SFCNF) matrix, Co1- x S nanoparticles, and CoN coatings, is prepared by integration of electrospinning and atomic layer deposition (ALD) technique. Representative results include the following: 1) ultrathin CoN layer is deposited by ALD on the surface of flexible substrate without any sacrifice of SFCNF and Co1- x S; 2) the composite exhibits strong electrocatalytic activity in both acidic and basic solutions. The overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are 20 and 180mV, respectively, at a current density of 10mA cm-2 in basic medium. A small Tafel slope of 54.4mV dec-1 is observed in 0.5 m H2 SO4 electrolyte; 3) tested as overall water splitting electrode, the composite records a current density of 10mA cm-2 at a relative low cell voltage of 1.58V and long-term stability for 20 h at a current density of up to 50mA cm-2 . The superior performance for overall water splitting is probably attributed to the synergistic effect of Co1- x S and ALD CoN. Specifically, implementation of ALD can be extended to innovate nanostructured materials for overall water splitting and even other renewable energy aspects.