Combining Porosification and Doping Strategy to Enhance the Catalytic Activity of NiCo2O4-Based Electrocatalysts for Efficient Water Splitting

Abstract

Low-cost electrocatalysts with high catalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are essential for electrochemical water splitting to produce hydrogen. In this study, we report the combination of porosification and doping strategy to improve the catalytic activity of NiCo₂O₄-based electrocatalysts for HER and OER. A facile porosification method was proposed and demonstrated by annealing the NiCo₂O₄ nanosheets in a reductive atmosphere to synthesize porous NiCo₂O₄ nanosheets. In order to further improve the catalytic activity for HER and OER, the porous NiCo₂O₄ nanosheets were doped with P and Fe, respectively, which tailored the electronic structure of the electrocatalysts, improved the intrinsic catalytic activity, and increased the number of active sites. HER or OER experiments were performed on the porous P-NiCo₂O₄ nanosheets or the porous NiCo_1.5Fe_0.5O₄ nanosheets, which required an overpotential of 160 mV or 222 mV to deliver a current density of 10 mA/cm², respectively. Furthermore, overall water splitting was achieved using the porous P-NiCo₂O₄ nanosheet cathode and the porous NiCo_2-xFe_xO₄ nanosheet anode with a Faraday Efficiency of 98.22%. The present paper proposes a strategy to fabricate doped porous electrocatalysts with a view to providing insights for the design and synthesis of efficient and inexpensive electrocatalysts for water splitting.

Graphical abstract