Vertically Aligned NiCo2S4 Nanosheets Deposited on N-Doped Graphene for Bifunctional and Durable Electrode of Overall Water Splitting

Developing non-noble metal electrocatalysts with high catalytic activity and stability is very important for practical water splitting technology. Herein, electrocatalytically active, bifunctional, and durable electrodes, are reported where NiCo2S4 nanosheets deposited onto nitrogen-incorporated reduced graphene oxide (N-rGO) are assembled onto 3D Ni foam. These freestanding binder-free electrodes exhibit excellent bifunctional catalytic activity for both hydrogen evolution and oxygen evolution reactions in alkaline condition, as well as overall water splitting reaction measured in a two-electrode configuration. The cell voltage is as low as 1.63 V to achieve a current density of 10 mA cm(-2) and this value is well preserved with negligible overpotential for more than 50 h. The results open a door to design bifunctional durable electrode based on non-noble metals for practical alkaline water electrolyzers.