Binder-free Fe-doped NiCo2O4/Ni3S4 hollow heterostructure nanotubes for highly efficient overall water splitting

Abstract

For overall water splitting, a vital challenge is to design active sites at interfaces. Heterogeneous catalysts with enhanced mass/charge transfer and accelerated adsorption of intermediates have exhibited significantly enhanced activities. Herein, a Fe-doped NiCo₂O₄/Ni₃S₄ heterogeneous electrocatalyst is synthesized for the HER and OER. On account of the synergistic effect of heterostructures, Ni–O–S presents a low overpotential of 29.1 mV (10 mA cm⁻²), a relatively small Tafel slope of 53.3 mV dec⁻¹ for the HER, and 259 mV at a current density of 100 mA cm⁻² (33.1 mV dec⁻¹) for the OER. What is more, Ni–O–S acts as a binder-free bi-functional electrode in an alkaline electrolyte for overall water splitting, exhibiting a cell voltage of 1.45 V (10 mA cm⁻²) with good stability. This work offers an efficient approach for designing stable and high-efficiency heterogeneous electrodes for overall water splitting.